Showing 1–50 of 274 results for author: Islam, M

Metallic Bonding-Driven Elastic Softness and Optical Response in the Mg-Rich Laves-Phase LaMg2

Authors: Farjana Mou, S. M. Nazmus Shakib Pias, M A Islam, Md Zahidur Rahaman

Abstract: A systematic first-principles investigation of the structural, electronic, mechanical, and optical properties of the cubic C15 Laves-phase intermetallic compound LaMg2 is performed within density functional theory. The calculated elastic constants satisfy the mechanical stability criteria for cubic crystals, confirming the intrinsic stability of the C15 phase. LaMg2 exhibits relatively low bulk, s… ▽ More A systematic first-principles investigation of the structural, electronic, mechanical, and optical properties of the cubic C15 Laves-phase intermetallic compound LaMg2 is performed within density functional theory. The calculated elastic constants satisfy the mechanical stability criteria for cubic crystals, confirming the intrinsic stability of the C15 phase. LaMg2 exhibits relatively low bulk, shear, and Young's moduli, indicating enhanced compressibility and elastic softness compared with transition-metal-based Laves phases. Direction-dependent elastic analysis reveals moderate anisotropy in Young's modulus, shear modulus, and Poisson's ratio, whereas linear compressibility remains nearly isotropic, consistent with the high crystallographic symmetry. The ductile nature of LaMg2 is supported by Pugh's ratio and Poisson's ratio, suggesting resistance to brittle failure and the dominance of metallic bonding. Electronic structure calculations confirm metallic behavior with a finite density of states at the Fermi level, primarily originating from La-5d states, accompanied by delocalized charge density characteristic of metallic interactions. The optical response further reflects the metallic nature through high reflectivity, strong optical conductivity at low photon energies, and pronounced absorption in the ultraviolet region. The combination of mechanical compliance, ductility, and metallic optical response highlights LaMg2 as a promising lightweight intermetallic material for applications requiring structural stability, damage tolerance, and efficient electromagnetic shielding or reflective components. △ Less

Submitted 10 August, 2026; originally announced August 2026.

Comments: 25 pages, 6 figures, 2 tables

Thermal and electrical conductivity of a refractory high-entropy alloy after high-pressure torsion: Electron versus phonon contributions

Authors: Jacqueline Hidalgo-Jimenez, Payam Edalati, Md Amirul Islam, Makoto Arita, Bidyut Baran Saha, Kaveh Edalati

Abstract: The equiatomic refractory high-entropy alloy TiZrHfNbTa was processed by high-pressure torsion (HPT) to investigate the effect of nanostructuring and defect engineering on thermal and electrical transport properties. Severe plastic deformation (SPD) via the HPT treatment induces substantial accumulation of dislocations, grain refinement to the nanometer level (average: 40 nm), and partial transfor… ▽ More The equiatomic refractory high-entropy alloy TiZrHfNbTa was processed by high-pressure torsion (HPT) to investigate the effect of nanostructuring and defect engineering on thermal and electrical transport properties. Severe plastic deformation (SPD) via the HPT treatment induces substantial accumulation of dislocations, grain refinement to the nanometer level (average: 40 nm), and partial transformation from the BCC phase to the omega phase. While hardness increases to a steady state with processing, the specific heat capacity exhibits a non-monotonic behavior: it decreases at low strains due to the suppression of low-frequency vibrational modes by dislocations, then partially recovers at high strains due to anharmonic vibrations at newly formed high-angle grain boundaries. Thermal conductivity decreases at low strains but shows a slight recovery at high strains, whereas electrical conductivity decreases monotonically to a steady state without recovery. Analysis using the Wiedemann-Franz law reveals that the electronic contribution dominates thermal transport, while the phononic contribution (limited by the scattering of phonons on defects) is only 11 to 23%, depending on the degree of straining. The contrasting evolution of thermal and electrical conductivity is ascribed to the transition from dislocation-dominated vibrations at low strains to grain boundary-dominated vibrations at high strains, which affects phonons and electrons with different efficiencies. △ Less

Submitted 21 July, 2026; originally announced July 2026.

Domain wall motion in ferromagnetic nanowires driven by a localized Gaussian thermal gradient

Authors: M. A. Jafar Pikul, M. A. S. Akanda, M. T. Islam

Abstract: We investigate magnetic domain wall (DW) dynamics in a uniaxial ferromagnetic nanowire under the localized Gaussian temperature profile of a laser spot using the stochastic Landau-Lifshitz-Gilbert equation. The DW velocity increases linearly with peak laser temperature and decreases with increasing laser to DW distance. The velocity varies nonlinearly with Gilbert damping because damping strengthe… ▽ More We investigate magnetic domain wall (DW) dynamics in a uniaxial ferromagnetic nanowire under the localized Gaussian temperature profile of a laser spot using the stochastic Landau-Lifshitz-Gilbert equation. The DW velocity increases linearly with peak laser temperature and decreases with increasing laser to DW distance. The velocity varies nonlinearly with Gilbert damping because damping strengthens thermal magnon excitation but shortens the magnon propagation length. The DW initially lies away from the laser-heated region, so the temperature gradient at its position is effectively zero and the entropic torque is negligible. The DW motion is therefore mainly driven by magnonic spin-transfer torque. We analyze laser temperature, laser to DW distance, damping, uniaxial anisotropy, and laser width. The analysis shows that laser width and laser to DW distance independently control the DW response. These findings may clarify the mechanism of localized thermally driven DW motion and guide thermal control strategies in spintronic racetrack-memory devices. △ Less

Submitted 14 July, 2026; originally announced July 2026.

Strain- and Electric-Field-Tunable Valley Polarization in Mo0.75V0.25Te2(Mo3VTe8) for Valleytronic Application

Authors: Md. Mostaqul Islam, Vivek Chowdhury, Md. Nure-Alam-Dipu, Ahmed Zubair

Abstract: Valley polarization in 2D TMDs is promising for low-power valleytronic and spin-valley information processing, but time-reversal symmetry in pristine nonmagnetic TMDs keeps the K+ and K- valleys degenerate, limiting device applications. In this work, we investigated the structural stability, electronic properties, and tunable valley polarization of V-alloyed MoTe2 monolayer, Mo0.75V0.25Te2, using… ▽ More Valley polarization in 2D TMDs is promising for low-power valleytronic and spin-valley information processing, but time-reversal symmetry in pristine nonmagnetic TMDs keeps the K+ and K- valleys degenerate, limiting device applications. In this work, we investigated the structural stability, electronic properties, and tunable valley polarization of V-alloyed MoTe2 monolayer, Mo0.75V0.25Te2, using first-principles density functional theory (DFT) calculations. Substitutional alloying of MoTe2 with V introduced magnetic exchange interaction, which, together with spin-orbit coupling (SOC), lifted the valley degeneracy at the unequal valleys. The alloyed structure was found to be energetically and dynamically stable due to the absence of imaginary phonon modes. In pristine MoTe2, SOC produced spin splittings of 34.0 meV and 218.9 meV in the conduction bands and valence bands, respectively, but no valley polarization was observed. In contrast, Mo0.75V0.25Te2 exhibited spontaneous valley polarization of 37.3 meV in the conduction band and 78.2 meV in the valence band. The valley polarization was further enhanced by external electric fields and biaxial strain. A transverse electric field along the crystal c axis produced the maximum valley splitting of 132.8 meV in the valence band, whereas biaxial tensile strain increased the valence band valley splitting up to 160.8 meV. The maximum conduction band valley splitting reached 54.4 meV under 2% biaxial compressive strain. These results demonstrated that V alloying, combined with electric-field and strain engineering, provides an effective strategy for achieving large and tunable valley polarization in MoTe2. Thus, Mo0.75V0.25Te2 can be considered a promising 2D platform for tunable valleytronic device applications, such as transistors and sensors. △ Less

Submitted 18 June, 2026; originally announced June 2026.

Precipitation strengthening: a collective multi-dislocation phenomenon

Authors: Mahmudul Islam, Nicolas Bertin, Sylvie Aubry, Vasily V. Bulatov, Rodrigo Freitas

Abstract: Precipitation strengthening is a cornerstone of physical metallurgy, delivering otherwise unattainable combinations of strength and ductility. The approach relies on nanoscale precipitates that impede the motion of dislocations, the primary carriers of plastic deformation. Historically, precipitation strengthening has been rationalized via two idealized, limiting mechanisms: dislocations either cu… ▽ More Precipitation strengthening is a cornerstone of physical metallurgy, delivering otherwise unattainable combinations of strength and ductility. The approach relies on nanoscale precipitates that impede the motion of dislocations, the primary carriers of plastic deformation. Historically, precipitation strengthening has been rationalized via two idealized, limiting mechanisms: dislocations either cut through or bow around precipitates. However, in situ experiments cannot yet resolve the coupled, real-time evolution of dislocation networks and nanoprecipitates, leaving these atomic-scale dynamics inaccessible to direct observation. Here, using large-scale atomistic simulations that fully capture these dynamics, we demonstrate that the classical cutting-versus-bowing dichotomy is incomplete. Instead, strengthening arises as an emergent collective phenomenon driven by concurrent, multi-dislocation interactions. These interactions simultaneously induce dislocation accumulation at interfaces, storage within precipitates, and precipitate-mediated multiplication inside the matrix. These findings establish a mechanistic framework that transcends traditional models and provides a new foundation for predicting strengthening behavior. △ Less

Submitted 12 June, 2026; originally announced June 2026.

Comments: 13 pages, 4 figures

Magnesium-graphene interphase boundaries created by high-pressure torsion enhance hydrogen storage kinetics:Mechanisms and significance of activation energy and frequency factor

Authors: Runchen Zhou, Payam Edalati, Anthony Alhayek, Shivam Dangwal, Marc Novelli, Md. Amirul Islam, Baran Bidyut Saha, Thierry Grosdidier, Kaveh Edalati

Abstract: A strategy to overcome sluggish hydrogenation/dehydrogenation of magnesium is demonstrated by creating magnesium-graphene interphase boundaries via high-pressure torsion (HPT). HPT reduces the grain size of pure magnesium from 1 mm to 850 nm, with 70% of grain boundaries having high misorientation angles. Graphene addition leads to even finer grain sizes of 10-500 nm with a bimodal morphology. The… ▽ More A strategy to overcome sluggish hydrogenation/dehydrogenation of magnesium is demonstrated by creating magnesium-graphene interphase boundaries via high-pressure torsion (HPT). HPT reduces the grain size of pure magnesium from 1 mm to 850 nm, with 70% of grain boundaries having high misorientation angles. Graphene addition leads to even finer grain sizes of 10-500 nm with a bimodal morphology. The magnesium-graphene composites exhibit superior kinetics at 623 K while maintaining high air resistance. Kinetic modeling reveals that the rate-controlling mechanism transits from interfacial reaction in coarse-grained magnesium to atomic diffusion in magnesium-graphene nanocomposites. Kissinger analysis shows that the activation energy for hydrogen desorption remains unchanged at 145 +/- 2 kJ/mol, regardless of the presence of grain or interphase boundaries. However, the frequency factor (number of successful attempts to overcome the activation energy) increases with the generation of interfaces, which serve as sites for hydrogen diffusion and heterogeneous metal/hydride nucleation. These findings highlight the impact of interphase boundary engineering via severe plastic deformation for enhancing the kinetics and air resistance of hydrogen storage materials. △ Less

Submitted 13 May, 2026; originally announced May 2026.

Can we teach generative artificial intelligence the design language of engineered living materials?

Authors: Andrés Díaz Lantada, José A. Yáñez, William Solórzano-Requejo, Monsur Islam

Abstract: This study presents a versatile ontology and a useful codification scheme for describing all kinds of engineered living materials (ELMs). The different components of the ontology, namely: families according to the taxonomy for ELMs, industrial applications and synthesis or processing methods, are systematically organized, enumerated, classified, codified and explained. The methodic application of… ▽ More This study presents a versatile ontology and a useful codification scheme for describing all kinds of engineered living materials (ELMs). The different components of the ontology, namely: families according to the taxonomy for ELMs, industrial applications and synthesis or processing methods, are systematically organized, enumerated, classified, codified and explained. The methodic application of the ontology to a set of 100 relevant examples of ELMs helps to demonstrate its utility and adaptability to many different types of ELMs with a wide range of industrial applications and obtained through numerous synthesis and processing methods. This proves that the developed ontology and codification schemes, with the glossary provided to support its implementation and application, can serve as a comprehensive classification tool for the emergent field of ELMs. Furthermore, the usability of the ELMs ontology and codification by a generative artificial intelligence (AI) is explored and validated by different means, checking that both natural language and the codification are understandable for describing ELMs, verifying that the generative AI adequately codifies examples of ELMs according to the ontology, and validating the synergic applicability of the ontology and codification with generative AI tools for illustrating novel ELMs and supporting their conceptual design. This study is expected to provide a universal language to facilitate communication in the ELMs field and to foster the discovery of new ELMs and related innovations, hoping it may accelerate scientific and technological discoveries. △ Less

Submitted 29 April, 2026; originally announced April 2026.

Dynamical magnetism in the disordered cubic lattice material $γ$-${\rm Ba}_{3}{\rm CoNb}_{2}{\rm O}_{9}$

Authors: Fanjun Xu, Ralf Feyerherm, Cecilie Glittum, Thomas J. Hicken, Hubertus Luetkens, Jonas A. Krieger, Cintli Aguilar-Maldonado, Sven Luther, Lucy K. Saunders, Clemens Ritter, Peter Fouquet, Margarita Russina, Karel Prokes, A. T. M. Nazmul Islam, Bella Lake

Abstract: $γ$-${\rm Ba}_{3}{\rm CoNb}_{2}{\rm O}_{9}$ realizes a disordered simple-cubic spin-$1/2$ lattice in which Co$^{2+}… ▽ More $γ$-${\rm Ba}_{3}{\rm CoNb}_{2}{\rm O}_{9}$ realizes a disordered simple-cubic spin-$1/2$ lattice in which Co$^{2+}$ ions randomly occupy one third of the sites, placing the system close to the site-percolation threshold for magnetic order. Specific-heat, susceptibility, neutron spin-echo, and muon spin-rotation measurements reveal a broad thermodynamic crossover, short-range magnetic correlations, and persistent fast spin dynamics down to at least 0.1~K, with no evidence for static order or conventional spin-glass freezing. Monte Carlo simulations yield a broad distribution of orphan spins, finite clusters, and an infinite network. The calculated orphan-spin fraction ($\approx 8.8\%$) agrees well with the weakly correlated spin fraction inferred from magnetization ($\approx 8.2\%$). Exact diagonalization of a diluted $S = 1/2$ Heisenberg model captures the broad magnetic specific-heat anomaly and supports the coexistence of weakly and strongly correlated spin environments. These results support a picture in which spin-$1/2$ quantum fluctuations, together with dilution and proximity to the percolation threshold, can support a disorder-driven dynamical state with short-range correlations in three dimensions, distinct from both classical spin glasses and geometrically frustrated quantum spin liquids. △ Less

Submitted 20 April, 2026; originally announced April 2026.

Comments: 17 pages, 15 figures

Half-quantized anomalous Hall conductance in topological insulator/ferromagnet van der Waals heterostructures

Authors: Shahid Sattar, Roman Stepanov, Alexander Tyner, M. F. Islam, A. H. MacDonald, C. M. Canali

Abstract: The half-quantized anomalous Hall conductance (AHC) in topological materials is a condensed matter physics realization of the parity anomaly of (2+1) quantum field theory and an important challenge for both theoretical and experimental research. A possible realization of this phenomenon may be achieved by interfacing a two-dimensional (2D) ferromagnetic (FM) layer with one surface of a thin slab o… ▽ More The half-quantized anomalous Hall conductance (AHC) in topological materials is a condensed matter physics realization of the parity anomaly of (2+1) quantum field theory and an important challenge for both theoretical and experimental research. A possible realization of this phenomenon may be achieved by interfacing a two-dimensional (2D) ferromagnetic (FM) layer with one surface of a thin slab of a topological insulator (TI), which breaks the otherwise conserved time-reversal symmetry, leading to a gap opening in the Dirac-like energy spectrum of the TI surface states. The resulting heterostructure can support chiral currents where only one spin channel contributes to transport, producing a half-quantized Hall conductance ($e^2/2h$). In this work, using first-principles methods together with tight-binding models, we investigate the magnetization-induced gap, the properties of the sidewalls states, and Hall conductance in three different FI/TI van der Waals heterostructures that are relevant for ongoing experiments. We also discuss the factors that can hinder the realization of exact half-quantization in a realistic system and their implication for the quantum anomalous Hall effect and the topological magnetoelectric effect. △ Less

Submitted 12 April, 2026; originally announced April 2026.

Comments: 9 pages, 5 figures

Structural Motif Selection in Fluorinated Metal-Organic Chalcogenides Driven by Ligand Electrostatics

Authors: Md. Saiful Islam, Tomoaki Sakurada, Yeongsu Cho

Abstract: Hybrid organic-inorganic materials enable systematic structural tuning through chemical modification of organic ligands. Predictive control, however, requires mechanistic understanding of how ligand chemistry and inorganic frameworks jointly determine structural motif selection. Metal-organic chalcogenides (MOCs), where metal-chalcogenide units are covalently bonded to organic ligands, offer an id… ▽ More Hybrid organic-inorganic materials enable systematic structural tuning through chemical modification of organic ligands. Predictive control, however, requires mechanistic understanding of how ligand chemistry and inorganic frameworks jointly determine structural motif selection. Metal-organic chalcogenides (MOCs), where metal-chalcogenide units are covalently bonded to organic ligands, offer an ideal platform in which ligand substitution directly alters crystal structure. Here, we investigate silver selenide-based MOCs with fluorinated phenyl ligands to elucidate governing interactions. Density functional theory with fragment-based energy analysis identifies ligand-ligand interactions as the primary energetic driver of motif selection. Symmetry-adapted perturbation theory further decomposes ligand-ligand interactions and shows that electrostatic interactions are decisive in selecting the preferred motif by selectively stabilizing specific packing arrangements. The results further show that ligand orientation controls the effectiveness of long-range electrostatic interactions, establishing a physically grounded design principle for directing structural motifs in MOCs through targeted control of ligand packing and electrostatics. △ Less

Submitted 10 April, 2026; originally announced April 2026.

Single-Crystal Growth and Magnetic, Electronic Properties of the FCC Antiferromagnet Ba_2CoMoO_6

Authors: A. R. N. Hanna, M. M. Ferreira-Carvalho, S. H. Chen, C. F. Chang, C. Y. Kuo, A. T. M. N. Islam, R. Feyerherm, L. H. Tjeng, B. Lake

Abstract: This work presents a comprehensive investigation of the structural, magnetic, and electronic properties of the double perovskite Ba$_2$CoMoO$_6$ (BCMO). Single crystals were grown via floating-zone and Czochralski techniques and characterized using a set of complementary methods. X-ray diffraction analysis confirmed that BCMO crystallizes in a face-centered cubic structure with space group… ▽ More This work presents a comprehensive investigation of the structural, magnetic, and electronic properties of the double perovskite Ba$_2$CoMoO$_6$ (BCMO). Single crystals were grown via floating-zone and Czochralski techniques and characterized using a set of complementary methods. X-ray diffraction analysis confirmed that BCMO crystallizes in a face-centered cubic structure with space group $Fm\bar{3}m$. Magnetic susceptibility measurements reveal antiferromagnetic ordering below $T_\mathrm{N} = 20.1(1)$~K, with a spin-flop transition at $μ_0 H = 2.65$~T. Heat-capacity measurements and entropy analysis, $ΔS \approx 0.95\,R\ln 2$, are consistent with a $J_\mathrm{eff} = \tfrac{1}{2}$ effective ground state for Co$^{2+}$ ions. X-ray absorption spectroscopy at the Co~$L_{2,3}$ edges provides insight into the local electronic structure, revealing spin-orbit and crystal-field splitting effects; cluster-model calculations constrained by the XAS spectra yield a Landé $g$ factor $g = 4.52$, consistent with a spin-orbit-entangled $J_\mathrm{eff} = \tfrac{1}{2}$ ground state. Surface photovoltage spectroscopy reveals a strong optical response with a prominent feature at $2.65$~eV. These findings advance the understanding of face-centered cubic lattice antiferromagnets with strong spin-orbit coupling and suggest the technological promise of BCMO for spintronic and energy-conversion applications. △ Less

Submitted 16 March, 2026; originally announced March 2026.

A systematic study of single molecule metallocenes with 4d and 3d transition metal atoms

Authors: Daniela Herrera-Molina, Kushantha P. K. Withanage, Jesus N. Pedroza-Montero, Pardeep Kaur, Mark. R. Pederson, M. F. Islam

Abstract: The realization of spin-based devices remains one of the central goals of spintronics research. Single-molecule magnets (SMMs) constitute an important class of nanoscale magnetic systems with significant potential for spintronic applications, where individual molecules can serve as fundamental building blocks of functional devices. In this work, we systematically investigate a family of 4d and 3d… ▽ More The realization of spin-based devices remains one of the central goals of spintronics research. Single-molecule magnets (SMMs) constitute an important class of nanoscale magnetic systems with significant potential for spintronic applications, where individual molecules can serve as fundamental building blocks of functional devices. In this work, we systematically investigate a family of 4d and 3d transition-metal metallocenes using first-principles density functional theory. Among the seven 4d metallocenes considered, only Mo and Rh metallocenes undergo Jahn Teller distortions and exhibit uniaxial anisotropy with energy barriers of approximately 20 K. Similarly, among the 3d metallocenes studied in this work, only Cr and Co metallocenes undergo Jahn Teller distortions and display uniaxial anisotropy, although with smaller barriers below 10 K. All remaining metallocenes exhibit easy-plane anisotropy. We find that the magnetic anisotropy energy does not increase monotonically with the number of d electrons; instead, it is governed primarily by the orbital ordering of the transition-metal d states. Our calculations further show that the Jahn Teller distortion induces transverse anisotropy, leading to zero-field magnetization tunneling across the energy barrier, with the weakest tunneling rate for Mo metallocene. For the Mo metallocene, the magnetic anisotropy energy increases to approximately 60 K in cationic charge states, although the magnetic anisotropy changes from uniaxial to easy-plane. In this work, we also investigate the influence of ligand size on the structural stability of metallocenes and establish practical guidelines for constructing reliable molecular models for first-principles studies. Finally, we also propose that metallocenes with easy-plane anisotropy could serve as magnetic sensing elements, highlighting their potential beyond memory applications. △ Less

Submitted 28 July, 2026; v1 submitted 10 March, 2026; originally announced March 2026.

Comments: 14 pages, 8 figures

Crystal growth and magnetic properties of spin-$1/2$ distorted triangular lattice antiferromagnet CuLa$_2$Ge$_2$O$_8$

Authors: S. Thamban, C. Aguilar-Maldonado, S. Chillal, R. Feyerherm, K. Prokeš, A. J. Studer, D. Abou-Ras, K. Karmakar, A. T. M. N. Islam, B. Lake

Abstract: CuLa$_2$Ge$_2$O$_8$ forms a distorted triangular lattice of quantum spin-1/2 Cu$^{2+}$ ions. A crystal growth method was developed using the traveling-solvent floating zone technique resulting in the synthesis of a large single crystal (4 mm$\times$4 mm$\times$10 mm). The crystal was characterized with regard to phase purity and crystallinity using powder X-ray diffraction, energy dispersive X-ray… ▽ More CuLa$_2$Ge$_2$O$_8$ forms a distorted triangular lattice of quantum spin-1/2 Cu$^{2+}$ ions. A crystal growth method was developed using the traveling-solvent floating zone technique resulting in the synthesis of a large single crystal (4 mm$\times$4 mm$\times$10 mm). The crystal was characterized with regard to phase purity and crystallinity using powder X-ray diffraction, energy dispersive X-ray analysis and Laue diffraction, and found to be of excellent quality. The magnetic properties were characterized using dc-susceptibility, magnetization, and heat capacity measurements which revealed weak magnetic frustration with long-range magnetic order occurring below $T_N=1.14(1)$~K. The magnetic structure determined using neutron powder diffraction is a commensurate, noncollinear antiferromagnetic, different from the 120$^{\circ}$ order of an equilateral triangular antiferromagnet. The ordered moments lie in the {\bf bc}-plane, with components $m_b=0.50(3)$~$μ_{B}$ and $m_c= 0.73(5)$~$μ_{B}$ along the {\bf b}- and {\bf c}-axes respectively, giving a total ordered moment of $M_{total}$= 0.89(6)$μ_{B}/$Cu$^{2+}$ at 20~mK. △ Less

Submitted 5 March, 2026; v1 submitted 5 March, 2026; originally announced March 2026.

Comments: 11 pages, 13 figures

Majorana Fermions in spin up and down electronic complexes in spin-orbit coupled array of semiconductor quantum dots in proximity to $s$-type superconductor and in magnetic field

Authors: Mijanur Islam, Mahan Mohseni, Ibsal Assi, Daniel Miravet, Pawel Hawrylak

Abstract: Semiconductor-s-type superconductor nanowires host spinful fermions and cannot be reduced to a single spinless Kitaev chain hosting single Majorana zero mode. Instead, such systems can be converted into two coupled p-wave Kitaev-like chains associated with different spin sectors. Using the bond Fermion transformation and exact diagonalization, we analyze parity resolved spectra and local spectral… ▽ More Semiconductor-s-type superconductor nanowires host spinful fermions and cannot be reduced to a single spinless Kitaev chain hosting single Majorana zero mode. Instead, such systems can be converted into two coupled p-wave Kitaev-like chains associated with different spin sectors. Using the bond Fermion transformation and exact diagonalization, we analyze parity resolved spectra and local spectral functions, demonstrating that zero-energy modes strongly localized at the system boundaries emerge only in one effective chain. Inter-chain coupling lifts parity degeneracy and redistributes the low-energy spectral weight, providing a controlled framework to assess the stability of Majorana-like modes in the finite spinful nanowires. △ Less

Submitted 26 January, 2026; v1 submitted 20 January, 2026; originally announced January 2026.

Comments: 10 pages, 7 figures, comments are welcome

DFT modelling of stacking faults in hexagonal and cubic GaN

Authors: Zijie Wang, Mazharul M. Islam, David R. Bowler

Abstract: We have performed density functional theory (DFT) calculations to characterize the energetics, and the atomic and electronic structure, of stacking faults in GaN, both in the stable hexagonal wurtzite (wz) phase and in the metastable cubic zincblende (zb) phase. In wz GaN, SFs on the (0001) planes can be divided into three different intrinsic stacking faults (I1, I2, and I3) and oneextrinsic stack… ▽ More We have performed density functional theory (DFT) calculations to characterize the energetics, and the atomic and electronic structure, of stacking faults in GaN, both in the stable hexagonal wurtzite (wz) phase and in the metastable cubic zincblende (zb) phase. In wz GaN, SFs on the (0001) planes can be divided into three different intrinsic stacking faults (I1, I2, and I3) and oneextrinsic stacking fault (E). In zb GaN, SFs form along (111) directions, giving one type each of intrinsic, extrinsic and twin SFs. Based on the calculated formation energy, I1 is the most stable SF of wz GaN in agreement with experiment. For zb GaN, the intrinsic stacking fault is the most dominant planar defect. To characterize the effect of the stacking faults on the electronic structure of the material, we examined the band density. We found that the bands near the valence band maximum in wz GaN are localised on the Ga-polar side of the stacking fault (i.e. on the Ga side of the Ga-N bonds perpendicular to the SF), with the bands near the conduction band minimum more on the N-polar side, though somewhat delocalised. We found the opposite trend in zb GaN; this behaviour is caused by a redistribution of charge near the interface. We also show the band offsets for the stacking faults, finding that they are very sensitive to local conditions, but can all be described as type II interfaces, with the presence of a stacking fault reducing the gap locally. △ Less

Submitted 1 July, 2026; v1 submitted 16 January, 2026; originally announced January 2026.

Comments: Contains supplementary information as appendix; 7 figures in main text. Submitted to Phys. Rev. B

Journal ref: Phys. Rev. B 114, 115303 (2026)

DataScribe: An AI-Native, Policy-Aligned Web Platform for Multi-Objective Materials Design and Discovery

Authors: Divyanshu Singh, Doguhan Sarıtürk, Cameron Lea, Md Shafiqul Islam, Raymundo Arroyave, Vahid Attari

Abstract: The acceleration of materials discovery requires digital platforms that go beyond data repositories to embed learning, optimization, and decision-making directly into research workflows. We introduce DataScribe, an AI-native, cloud-based materials discovery platform that unifies heterogeneous experimental and computational data through ontology-backed ingestion and machine-actionable knowledge gra… ▽ More The acceleration of materials discovery requires digital platforms that go beyond data repositories to embed learning, optimization, and decision-making directly into research workflows. We introduce DataScribe, an AI-native, cloud-based materials discovery platform that unifies heterogeneous experimental and computational data through ontology-backed ingestion and machine-actionable knowledge graphs. The platform integrates FAIR-compliant metadata capture, schema and unit harmonization, uncertainty-aware surrogate modeling, and native multi-objective multi-fidelity Bayesian optimization, enabling closed-loop propose-measure-learn workflows across experimental and computational pipelines. DataScribe functions as an application-layer intelligence stack, coupling data governance, optimization, and explainability rather than treating them as downstream add-ons. We validate the platform through case studies in electrochemical materials and high-entropy alloys, demonstrating end-to-end data fusion, real-time optimization, and reproducible exploration of multi-objective trade spaces. By embedding optimization engines, machine learning, and unified access to public and private scientific data directly within the data infrastructure, and by supporting open, free use for academic and non-profit researchers, DataScribe functions as a general-purpose application-layer backbone for laboratories of any scale, including self-driving laboratories and geographically distributed materials acceleration platforms, with built-in support for performance, sustainability, and supply-chain-aware objectives. △ Less

Submitted 12 January, 2026; originally announced January 2026.

Detecting the Onset and Progression of Spinodal Decomposition using Transient Grating Spectroscopy

Authors: Maxwell Rae, Merrill Chiang, Mahmudul Islam, Angus P. C. Wylie, Avery Nguyen, Myles Stapelberg, Saleem A. Al Dajani, Kristýna Repček, Tomáš Grabec, Abby Kaplan, Rodrigo Freitas, Michael P. Short

Abstract: Spinodal decomposition can degrade corrosion resistance and embrittle materials. The ability to quickly, conclusively, and non-destructively detect the onset of spinodal decomposition before catastrophic materials degradation would represent a significant advance in materials testing. We demonstrate that spinodal decomposition can be detected in binary Fe-Cr alloys via modulus stiffening using in… ▽ More Spinodal decomposition can degrade corrosion resistance and embrittle materials. The ability to quickly, conclusively, and non-destructively detect the onset of spinodal decomposition before catastrophic materials degradation would represent a significant advance in materials testing. We demonstrate that spinodal decomposition can be detected in binary Fe-Cr alloys via modulus stiffening using in situ and ex situ transient grating spectroscopy (TGS). The key mechanistic insight is the non-linearity in elastic moduli as function of Cr content renders a spinodally decomposed Fe-Cr alloy stiffer than an equivalent solid solution for a certain range of initial chromium compositions. We confirm the presence of spinodal decomposition in the 36 at.% chromium alloy using differential scanning calorimetry (DSC), linked to known spinodal decomposition energetics, and show via atomistic simulations that elastic modulus stiffening is expected after spinodal decomposition in the 36 at.% chromium alloy. The results of this study suggest the potential use of TGS as a practical tool for non-destructive evaluation of key materials susceptible to such degradation. △ Less

Submitted 10 January, 2026; originally announced January 2026.

Configurable antiferromagnetic domains and lateral exchange bias in atomically thin CrPS4

Authors: Yu-Xuan Wang, Thomas K. M. Graham, Ricardo Rama-Eiroa, Md Ariful Islam, Mohammad H. Badarneh, Rafael Nunes Gontijo, Ganesh Prasad Tiwari, Tibendra Adhikari, Xin-Yue Zhang, Kenji Watanabe, Takashi Taniguchi, Claire Besson, Elton J. G. Santos, Zhong Lin, Brian B. Zhou

Abstract: Interfacial exchange coupling between antiferromagnets (AFMs) and ferromagnets (FMs) crucially makes it possible to shift the FM hysteresis, known as exchange bias, and to switch AFM states. Two-dimensional magnets unlock opportunities to combine AFM and FM materials; however, the buried AFM-FM interfaces obtained by stacking remains challenging to understand. Here we demonstrate interfacial contr… ▽ More Interfacial exchange coupling between antiferromagnets (AFMs) and ferromagnets (FMs) crucially makes it possible to shift the FM hysteresis, known as exchange bias, and to switch AFM states. Two-dimensional magnets unlock opportunities to combine AFM and FM materials; however, the buried AFM-FM interfaces obtained by stacking remains challenging to understand. Here we demonstrate interfacial control via intralayer exchange coupling in the layered AFM CrPS$_4$, where connected even and odd layers realize pristine lateral interfaces between AFM-like and FM-like regions. We distinguish antiphase even-layer states by scanning nitrogen-vacancy centre (NV) magnetometry due to a weak surface magnetization. This surface magnetization enables control over the even-layer state, with different regions switching at distinct fields due to their own lateral couplings. We toggle three AFM domains adjacent to a FM-like region and demonstrate a tunable multilevel exchange bias. Our nanoscale visualization unveils the microscopic origins of exchange bias and advances single two-dimensional crystals for hybrid AFM-FM technologies. △ Less

Submitted 3 December, 2025; originally announced December 2025.

Comments: 16 pages, 5 figures

Journal ref: Nature Materials 24, 1414-1423 (2025)

Ligand Engineering for Precise Control of Ultrathin CsPbI3 Nanoplatelet Superlattices for Efficient Light-Emitting Diodes

Authors: Jongbeom Kim, Woo Hyeon Jeong, Junzhi Ye, Allison Nicole Arber, Vikram, Donghan Kim, Yi-Teng Huang, Yixin Wang, Dongeun Kim, Dongryeol Lee, Chia-Yu Chang, Xinyu Shen, Sung Yong Bae, Ashish Gaurav, Akshay Rao, Henry J. Snaith, M. Saiful Islam, Bo Ram Lee, Myoung Hoon Song, Robert L. Z. Hoye

Abstract: Strongly-confined perovskite nanoplatelets (PeNPLs) offer opportunities not found in conventional isotropic nanocubes, especially in producing linearly polarized light, as well as enhancing outcoupling through control over the transition dipole moment. But this requires ultrathin nanoplatelets with three or fewer monolayers of PbI6 octahedra across the thickness, which are challenging to synthesis… ▽ More Strongly-confined perovskite nanoplatelets (PeNPLs) offer opportunities not found in conventional isotropic nanocubes, especially in producing linearly polarized light, as well as enhancing outcoupling through control over the transition dipole moment. But this requires ultrathin nanoplatelets with three or fewer monolayers of PbI6 octahedra across the thickness, which are challenging to synthesise uniformly, and their luminescence is strongly affected by surface defects. Together, these limit the performance of ultrathin PeNPLs in light-emitting diodes (LEDs). Here, we address these challenges with an ancillary ligand engineering strategy. We demonstrate that ligands with phosphoryl functional groups strongly bind to the perovskite surface, while having an organic backbone that is not sterically bulky ensures high ligand density. By modulating nucleation and growth, these ancillary ligands lead to monodisperse PeNPLs that stack more uniformly when self-assembled into superlattices, with suppressed agglomeration. As a result, from edge-up PeNPL superlattices, we achieve enhanced degree of polarization, while from face-down PeNPL superlattices, we achieve enhanced outcoupling that results in LEDs with 13.1% external quantum efficiency, the highest reported for ultrathin PeNPL LEDs. This work establishes ancillary ligand-induced synthesis as a decisive route to achieve uniform nanoplatelets with robust orientation control, enabling full utilization of the multifunctionality of anisotropic PeNPLs. △ Less

Submitted 23 January, 2026; v1 submitted 14 November, 2025; originally announced November 2025.

Comments: 25 pages, 4 figures, 1 table

Analog-to-Digital Converter Based on Voltage-controlled Superconducting Device

Authors: Md Mazharul Islam, Connor A. Good, Diego Ferrer, Juan P. Mendez, Denis Mamaluy, Wei Pan, Kathleen E Hamilton, Ahmedullah Aziz

Abstract: The increasing demand for cryogenic electronics in superconducting and quantum computing systems calls for ultra energy efficient data conversion architectures that remain functional at deep cryogenic temperatures.In this work, we present the first design of a voltage-controlled superconducting flash analog-to-digital converter (ADC) based on a novel quantum enhanced Josephson junction field effec… ▽ More The increasing demand for cryogenic electronics in superconducting and quantum computing systems calls for ultra energy efficient data conversion architectures that remain functional at deep cryogenic temperatures.In this work, we present the first design of a voltage-controlled superconducting flash analog-to-digital converter (ADC) based on a novel quantum enhanced Josephson junction field effect transistor (JJFET).Exploiting its strong gate tunability and transistor-like behavior, the JJFET offers a scalable alternative to conventional current controlled superconducting devices while aligning naturally with CMOS style design methodologies.Building on our previously developed Verilog A compact model calibrated to experimental data, we design and simulate a three bit JJFET based flash ADC.The core comparator block is realized through careful bias current selection and augmented with a three terminal nanocryotron to precisely define reference voltages.Cascaded JJFET comparators ensure robust voltage gain, cascadability, and logic level restoration across stages.Simulation results demonstrate accurate quantization behavior with ultra-low power dissipation, underscoring the feasibility of voltage driven superconducting mixed signal circuits.This work establishes a critical step toward unifying superconducting logic and data conversion, paving the way for scalable cryogenic architectures in quantum classical co-processors, low-power AI accelerators, and next generation energy constrained computing platforms. △ Less

Submitted 4 November, 2025; originally announced November 2025.

Design and Modeling of CdGa2Te4 and ZnGa2Te4 Chalcogenide Compound-Based Photovoltaic Devices: A DFT Study along with SCAPS-1D Simulation

Authors: Md Hasan Shahriar Rifat, Tanvir Khan, Md Arafat Hossain Shourov, Md Sahat Bin Sayed, Md Saiful Islam

Abstract: The electronic and optical properties of CdGa2Te4 and ZnGa2Te4 were studied using first-principles DFT calculations. Band gaps were calculated using the GGA-PBESol functional. Both materials show promise for photovoltaic applications because of their large, near-unity absorption efficiencies (10^4 cm^-1) in the visible region. They exhibit low exciton binding energies (18.85-26.81 meV), large Bohr… ▽ More The electronic and optical properties of CdGa2Te4 and ZnGa2Te4 were studied using first-principles DFT calculations. Band gaps were calculated using the GGA-PBESol functional. Both materials show promise for photovoltaic applications because of their large, near-unity absorption efficiencies (10^4 cm^-1) in the visible region. They exhibit low exciton binding energies (18.85-26.81 meV), large Bohr radii (23-34.3 Angstrom), and moderate exciton temperatures (218-311 K), which are favorable for photovoltaic applications. Their performance as solar cells was simulated using the SCAPS-1D tool for thin-film devices with Pt/CdS/CdGa2Te4/Cu2O/Ti and Pt/CdS/ZnGa2Te4/Cu2O/Ti structures. We investigated the effects of layer thickness, donor and acceptor concentrations (shallow donors/acceptors), and defect density on device performance. The ideal absorber thickness for XGa2Te4 (X = Cd, Zn) was found to be 1000-1800 nm, and the CdS buffer layer around 100 nm. To obtain an efficiency above 20%, the defect density in the CdGa2Te4 and ZnGa2Te4 absorber layers should be kept below 1.772 x 10^13 cm^-3. The best simulations show efficiencies of 18.46% and 17.35% for CdGa2Te4- and ZnGa2Te4-based solar cells, respectively. △ Less

Submitted 18 October, 2025; v1 submitted 6 October, 2025; originally announced October 2025.

Comments: 33 pages, 8 figures

Multifunctional Oxide Nanosheets: Frictional, Hall, and Piezoelectric Deformation of 2D Ga2O3

Authors: Md Akibul Islam, Uichang Jeong, Nima Barri, Azmeera Jannat, Ali Zavabeti, Seungbum Hong, Tobin Filleter

Abstract: Atomically thin oxides are increasingly recognized as an emerging class of 2D materials, yet their multifunctional properties have been far less investigated compared to other layered materials. Among these, gallium oxide is distinguished by its ultrawide bandgap, thermal stability, and mechanical rigidity, positioning it as a candidate material for nanoelectromechanical systems. In this study, th… ▽ More Atomically thin oxides are increasingly recognized as an emerging class of 2D materials, yet their multifunctional properties have been far less investigated compared to other layered materials. Among these, gallium oxide is distinguished by its ultrawide bandgap, thermal stability, and mechanical rigidity, positioning it as a candidate material for nanoelectromechanical systems. In this study, the tribological, transport, and electromechanical properties of beta-Ga2O3 nanosheets were probed using atomic force microscopy (AFM)--based techniques. Friction force microscopy (FFM) was used to investigate interfacial sliding, and a dependence of friction on external bias was observed, which was attributed to defect-mediated charge trapping. Van der Pauw Hall measurements were conducted up to 400 $^{\circ}$C, through which the ultrawide bandgap nature of beta-Ga2O3 was confirmed, as electronic transport remained suppressed despite high thermal activation. Piezoresponse force microscopy (PFM) was further applied, and a measurable converse electromechanical response on the order of a few pm/V was revealed, consistent with oxygen-vacancy--induced symmetry breaking. By integrating tribological, electrical, and electromechanical measurements, it was demonstrated that beta-Ga2O3 nanosheets present a unique platform in which insulating stability, bias-tunable interfacial mechanics, and defect-enabled electromechanical activity coexist, offering new opportunities for multifunctional oxide nanodevices. △ Less

Submitted 2 October, 2025; originally announced October 2025.

Comments: NA

Pristine and transition metal doped 2D AlSb as high performance electrocatalyst for selective CO2 reduction: A first-principles study

Authors: Md. Mostaqul Islam, Ahmed Zubair

Abstract: Electrochemical CO2 reduction reaction (CO2RR) using 2D nanomaterials has emerged as a sophisticated approach to mitigate industrial CO2 emissions. In this work, the potential application of pristine as well as strategically Fe, Co, Ni-doped 2D AlSb was examined as a CO2RR electrocatalyst. The recation pathways of CO2RR intermediate complexes, overpotential, stability, efficiency, and selectivity… ▽ More Electrochemical CO2 reduction reaction (CO2RR) using 2D nanomaterials has emerged as a sophisticated approach to mitigate industrial CO2 emissions. In this work, the potential application of pristine as well as strategically Fe, Co, Ni-doped 2D AlSb was examined as a CO2RR electrocatalyst. The recation pathways of CO2RR intermediate complexes, overpotential, stability, efficiency, and selectivity were studied using density functional theory (DFT). Outstanding overpotentials were achieved with pristine and doped 2D AlSb: Ni-doped 2D AlSb was selective for HCOOH (0.12eV) and CH4 (0.28eV), and Fe-doped 2D AlSb for HCHO (0.31eV) and CH3OH (0.31eV). The opposing effects of hydrogen evolution reaction (HER) was mitigated with the application of electric potential and solution pH. The main reasons for the enhancement of catalytic effect due to doping with Fe, Co, and Ni are bandgap reduction and creation of states at the edge of the valence band due to the 3d orbitals of these dopants. Interestingly, the Fe-doped 2D AlSb catalyst exhibited the highest catalytic activity. Excellent electrocatalytic properties of pristine and doped 2D AlSb make them suitable as CO2RR catalysts contributing towards a green and sustainable energy ecosystem. △ Less

Submitted 21 September, 2025; v1 submitted 14 September, 2025; originally announced September 2025.

Cavity-induced Eliashberg effect: superconductivity vs charge density wave

Authors: Md Mursalin Islam, Michele Pini, R. Flores-Calderón, Francesco Piazza

Abstract: Recent experiments have shown that non-equilibrium effects can play a key role in cavity-based control of material phases, notably in systems with charge-density-wave order. Motivated by this, we extend the theory of the Eliashberg effect, originally developed for superconducting phases, to charge-density-wave phases. Starting from a minimal electronic model where superconductivity and charge-dens… ▽ More Recent experiments have shown that non-equilibrium effects can play a key role in cavity-based control of material phases, notably in systems with charge-density-wave order. Motivated by this, we extend the theory of the Eliashberg effect, originally developed for superconducting phases, to charge-density-wave phases. Starting from a minimal electronic model where superconductivity and charge-density-wave order are equivalent at equilibrium, we introduce coupling to cavity photons, which are in turn coupled to an environment at a temperature different from the one of the electronic environment. This drives the system into a non-thermal steady state, which breaks the equivalence between superconductivity and charge-density-wave order. In the superconducting case, we recover the known behavior: a shift from continuous to discontinuous phase transitions with bistability. In contrast, the charge-density-wave case displays richer behavior: tuning the cavity frequency induces both continuous and discontinuous transitions, two distinct ordered phases, and a bistable regime ending at a critical point. These findings demonstrate that the scope of cavity-based non-thermal control of quantum materials is broader than at thermal equilibrium, and strongly depends on the targeted phases. △ Less

Submitted 9 September, 2025; originally announced September 2025.

Comments: Main text: 8 pages, 5 figures; Supplemental material: 21 pages, 2 figures

Dislocation-mediated short-range order evolution during thermomechanical processing

Authors: Mahmudul Islam, Killian Sheriff, Rodrigo Freitas

Abstract: Thermomechanical processing alters the microstructure of metallic alloys through coupled plastic deformation and thermal exposure, with dislocation motion driving plasticity and microstructural evolution. Our previous work (Islam et al., 2025) showed that the same dislocation motion both creates and destroys chemical short-range order (SRO), driving alloys into far-from-equilibrium SRO states. How… ▽ More Thermomechanical processing alters the microstructure of metallic alloys through coupled plastic deformation and thermal exposure, with dislocation motion driving plasticity and microstructural evolution. Our previous work (Islam et al., 2025) showed that the same dislocation motion both creates and destroys chemical short-range order (SRO), driving alloys into far-from-equilibrium SRO states. However, the connection between this dislocation-mediated SRO evolution and processing parameters remains largely unexplored. Here, we perform large-scale atomistic simulations of thermomechanical processing of equiatomic TiTaVW to determine how temperature and strain rate control SRO via competing creation ($Γ$) and annihilation ($λ$) rates. The simulations employ systems containing 2.4 million atoms and utilize a machine learning interatomic potential optimized to capture chemical complexity through the motif-based sampling technique. Using information-theoretic metrics, we quantify that the magnitude and chemical character of SRO vary systematically with processing parameters. We identify two regimes: a low-temperature regime with weak strain-rate sensitivity, and a high-temperature regime in which reduced dislocation density and increased screw character amplify chemical bias and accelerate SRO formation. The resulting steady-state SRO is far-from-equilibrium and cannot be produced by equilibrium thermal annealing. Together, these results provide a mechanistic and predictive link between processing parameters, dislocation physics, and SRO evolution in chemically complex alloys. △ Less

Submitted 23 December, 2025; v1 submitted 18 August, 2025; originally announced August 2025.

Comments: 15 pages, 5 figures. Acta Materialia (2025)

High-magnitude, spatially programmable, and sustained strain engineering of 2D semiconductors

Authors: Boran Kumral, Pedro Guerra Demingos, Peter Serles, Shuo Yang, Da Bin Kim, Dian Yu, Akhil Nair, Akshat Rastogi, Nima Barri, Md Akibul Islam, Jane Howe, Cristina H Amon, Sjoerd Hoogland, Edward H. Sargent, Chandra Veer Singh, Tobin Filleter

Abstract: Crystalline two-dimensional (2D) semiconductors often combine high elasticity and in-plane strength, making them ideal for strain-induced tuning of electronic characteristics, akin to strategies used in silicon electronics. However, existing techniques have not achieved strain in 2D materials that is simultaneously high in magnitude (>1%), stable over long periods, and spatially programmable, mean… ▽ More Crystalline two-dimensional (2D) semiconductors often combine high elasticity and in-plane strength, making them ideal for strain-induced tuning of electronic characteristics, akin to strategies used in silicon electronics. However, existing techniques have not achieved strain in 2D materials that is simultaneously high in magnitude (>1%), stable over long periods, and spatially programmable, meaning the strain level can be deterministically engineered across different regions of a single 2D layer. Here, we apply spatially programmable biaxial strain (e_b) up to 2.2% with spatial resolution of 0.13 %e_b um-1 in monolayer MoS2 via conformal transfer onto patterned substrates fabricated using two-photon lithography. The induced strain is stable for months and enables local band gap tuning of ~0.4 eV in monolayer MoS2, ~25% of its intrinsic band gap. We further extend the approach to bilayer WS2-MoS2 heterostructures. This strain-engineering technique introduces a new regime of strain-enabled control in 2D semiconductors to support the development of wide-spectrum optoelectronic devices and nanoelectronics with engineered electronic landscapes. △ Less

Submitted 21 December, 2025; v1 submitted 1 August, 2025; originally announced August 2025.

Comments: 25 pages of main text with 6 figures and 35 pages of supplementary information with 22 figures

Reducing Data Requirements for Sequence-Property Prediction in Copolymer Compatibilizers via Deep Neural Network Tuning

Authors: Md Mushfiqul Islam, Nishat N. Labiba, Lawrence O. Hall, David S. Simmons

Abstract: Synthetic sequence-controlled polymers promise to transform polymer science by combining the chemical versatility of synthetic polymers with the precise sequence-mediated functionality of biological proteins. However, design of these materials has proven extraordinarily challenging, because they lack the massive datasets of closely related evolved molecules that accelerate design of proteins. Here… ▽ More Synthetic sequence-controlled polymers promise to transform polymer science by combining the chemical versatility of synthetic polymers with the precise sequence-mediated functionality of biological proteins. However, design of these materials has proven extraordinarily challenging, because they lack the massive datasets of closely related evolved molecules that accelerate design of proteins. Here we report on a new Artifical Intelligence strategy to dramatically reduce the amount of data necessary to accelerate these materials' design. We focus on data connecting the repeat-unit-sequence of a \emph{compatibilizer} molecule to its ability to reduce the interfacial tension between distinct polymer domains. The optimal sequence of these molecules, which are essential for applications such as mixed-waste polymer recycling, depends strongly on variables such as concentration and chemical details of the polymer. With current methods, this would demand an entirely distinct dataset to enable design at each condition. Here we show that a deep neural network trained on low-fidelity data for sequence/interfacial tension relations at one set of conditions can be rapidly tuned to make higher-fidelity predictions at a distinct set of conditions, requiring far less data that would ordinarily be needed. This priming-and-tuning approach should allow a single low-fidelity parent dataset to dramatically accelerate prediction and design in an entire constellation of related systems. In the long run, it may also provide an approach to bootstrapping quantitative atomistic design with AI insights from fast, coarse simulations. △ Less

Submitted 29 July, 2025; originally announced July 2025.

Comments: 23 pages, 6 figures

Unveiling Phonon Contributions to Thermal Transport and the Failure of the Wiedemann-Franz Law in Ruthenium and Tungsten Thin Films

Authors: Md. Rafiqul Islam, Pravin Karna, Niraj Bhatt, Sandip Thakur, Helge Heinrich, Daniel M. Hirt, Saman Zare, Christopher Jezewski, Rinus T. P. Lee, Kandabara Tapily, John T. Gaskins, Colin D. Landon, Sean W. King, Ashutosh Giri, Patrick E. Hopkins

Abstract: Thermal transport in nanoscale interconnects is dominated by intricate electron-phonon interactions and microstructural influences. As copper faces limitations at the nanoscale, tungsten and ruthenium have emerged as promising alternatives due to their substantial phonon contributions to thermal conductivity. Metals with stronger phonon-mediated thermal transport are particularly advantageous in n… ▽ More Thermal transport in nanoscale interconnects is dominated by intricate electron-phonon interactions and microstructural influences. As copper faces limitations at the nanoscale, tungsten and ruthenium have emerged as promising alternatives due to their substantial phonon contributions to thermal conductivity. Metals with stronger phonon-mediated thermal transport are particularly advantageous in nanoscale architectures, where phonons are less sensitive to size effects than electrons. Here, we show that phonons play a comparable role to electrons in the thermal transport of ruthenium and tungsten thin films, evidenced by deviations from the classical Wiedemann-Franz law. Elevated Lorenz numbers-1.9 and 2.7 times the Sommerfeld value for ruthenium and tungsten, respectively-indicate phonon contributions of 45% and 62% to total thermal conductivity. Comparisons of in-plane thermal conductivity from steady-state thermoreflectance and electron relaxation times from infrared ellipsometry reveal that phonon-mediated transport is insensitive to microstructural variations and scaling. Ultrafast infrared pump-probe measurements show that ruthenium exhibits a higher electron-phonon coupling factor than tungsten, consistent with the differing contributions of carriers to thermal transport. Molecular dynamics simulations and spectral energy density analysis confirm substantial phonon-driven thermal transport and mode-dependent phonon lifetimes. These results offer insights into phonon-driven thermal transport and provide design principles for selecting interconnects with enhanced thermal management. △ Less

Submitted 12 May, 2025; originally announced May 2025.

Multiscale modelling of thermally stressed superelastic polyimide

Authors: Jerome Samuel S, Puneet Kumar Patra, Md Rushdie Ibne Islam

Abstract: Many thermo-mechanical processes, such as thermal expansion and stress relaxation, originate at the atomistic scale. We develop a sequential multiscale approach to study thermally stressed superelastic polyimide to explore these effects. The continuum-scale smoothed particle hydrodynamics (SPH) model is coupled with atomistic molecular dynamics (MD) through constitutive modelling, where thermo-mec… ▽ More Many thermo-mechanical processes, such as thermal expansion and stress relaxation, originate at the atomistic scale. We develop a sequential multiscale approach to study thermally stressed superelastic polyimide to explore these effects. The continuum-scale smoothed particle hydrodynamics (SPH) model is coupled with atomistic molecular dynamics (MD) through constitutive modelling, where thermo-mechanical properties and equations of state are derived from MD simulations. The results are verified through benchmark problems of heat transfer. Finally, we analyse the insulating capabilities of superelastic polyimide by simulating the thermal response of an aluminium plate. The result shows a considerable reduction in the thermal stress, strain and temperature field development in the aluminium plate when superelastic polyimide is used as an insulator. The present work demonstrates the effectiveness of the multi-scale method in capturing thermo-mechanical interactions in superelastic polyimide. △ Less

Submitted 28 April, 2025; originally announced April 2025.

Comments: 25 pages, 17 figures

Two-stage evolution of magnetic correlations in spiral spin liquid material, Ca$_{10}$Cr$_{7}$O$_{28}$

Authors: Changhyun Koo, Jaena Park, Johannes Werner, Suheon Lee, Christian Balz, A. T. M. Nazmul Islam, Yugo Oshima, Bella Lake, Kwang-Yong Choi, Rüdiger Klingeler

Abstract: We present an X-band and tunable high-frequency/high-field electron spin resonance (HF-ESR) study of single-crystalline Ca$_{10}$Cr$_{7}$O$_{28}$, which constitutes alternating antiferromagnetic and ferromagnetic kagome bilayers. At high temperatures, a phonon-assisted relaxation process is evoked to account for the pronounced increase of the linewidth in an exchange-narrowing regime (… ▽ More We present an X-band and tunable high-frequency/high-field electron spin resonance (HF-ESR) study of single-crystalline Ca$_{10}$Cr$_{7}$O$_{28}$, which constitutes alternating antiferromagnetic and ferromagnetic kagome bilayers. At high temperatures, a phonon-assisted relaxation process is evoked to account for the pronounced increase of the linewidth in an exchange-narrowing regime ($k_{\rm B}T\gg J$). In contrast, at low temperatures ($k_{\rm B}T\lesssim J$), a power-law behavior in line narrowing is observed. Our data reveal two distinct power-law regimes for the linewidth which crossover at $T^*\approx 7.5$~K. Notably, the intriguing evolution of the ESR linewidth in this alternating kagome bilayer system with opposite sign of exchange interactions highlights distinct spin dynamics compared to those in a uniform kagome antiferromagnet. △ Less

Submitted 3 April, 2025; originally announced April 2025.

Comments: 7 pages, 6 figures

Journal ref: Phys. Rev. B 111, 125144 (2025)

Operating two exchange-only qubits in parallel

Authors: Mateusz T. Mądzik, Florian Luthi, Gian Giacomo Guerreschi, Fahd A. Mohiyaddin, Felix Borjans, Jason D. Chadwick, Matthew J. Curry, Joshua Ziegler, Sarah Atanasov, Peter L. Bavdaz, Elliot J. Connors, J. Corrigan, H. Ekmel Ercan, Robert Flory, Hubert C. George, Benjamin Harpt, Eric Henry, Mohammad M. Islam, Nader Khammassi, Daniel Keith, Lester F. Lampert, Todor M. Mladenov, Randy W. Morris, Aditi Nethwewala, Samuel Neyens , et al. (16 additional authors not shown)

Abstract: Semiconductors are among the most promising platforms to implement large-scale quantum computers, as advanced manufacturing techniques allow fabrication of large quantum dot arrays. Various qubit encodings can be used to store and manipulate quantum information on these quantum dot arrays. Regardless of qubit encoding, precise control over the exchange interaction between electrons confined in qua… ▽ More Semiconductors are among the most promising platforms to implement large-scale quantum computers, as advanced manufacturing techniques allow fabrication of large quantum dot arrays. Various qubit encodings can be used to store and manipulate quantum information on these quantum dot arrays. Regardless of qubit encoding, precise control over the exchange interaction between electrons confined in quantum dots in the array is critical. Furthermore, it is necessary to execute high-fidelity quantum operations concurrently to make full use of the limited coherence of individual qubits. Here, we demonstrate the parallel operation of two exchange-only qubits, consisting of six quantum dots in a linear arrangement. Using randomized benchmarking techniques, we show that issuing pulses on the five barrier gates to modulate exchange interactions in a maximally parallel way maintains the quality of qubit control relative to sequential operation. The techniques developed to perform parallel exchange pulses can be readily adapted to other quantum-dot based encodings. Moreover, we show the first experimental demonstrations of an iSWAP gate and of a charge-locking Pauli spin blockade readout method. The results are validated using cross-entropy benchmarking, a technique useful for performance characterization of larger quantum computing systems; here it is used for the first time on a quantum system based on semiconductor technology. △ Less

Submitted 3 October, 2025; v1 submitted 1 April, 2025; originally announced April 2025.

Wafer scale reactive sputtering of highly oriented and ferroelectric Al$_{0.6}$Sc$_{0.4}$N from 300 mm AlSc Targets

Authors: Tom-Niklas Kreutzer, Muhammad Zubair Ghori, Md Redwanul Islam, Fabian Lofink, Fabian Stoppel, Axel Müller-Groeling, Simon Fichtner

Abstract: This paper presents progress towards the large-scale manufacturability of piezo- and ferroelectric Al$_{1-x}$Sc$_x$N thin films with very high Sc content. Al$_{0.6}$Sc$_{0.4}$N layers were deposited by reactive sputtering from a 300 mm diameter Al$_{0.6}$Sc$_{0.4}$N target on standard 200 mm Si wafers with Pt bottom- and Mo top-electrodes. The deposited films were analyzed in depth with X-Ray diff… ▽ More This paper presents progress towards the large-scale manufacturability of piezo- and ferroelectric Al$_{1-x}$Sc$_x$N thin films with very high Sc content. Al$_{0.6}$Sc$_{0.4}$N layers were deposited by reactive sputtering from a 300 mm diameter Al$_{0.6}$Sc$_{0.4}$N target on standard 200 mm Si wafers with Pt bottom- and Mo top-electrodes. The deposited films were analyzed in depth with X-Ray diffraction (XRD), Reciprocal Space Mapping (RSM), Scanning electron microscopy (SEM) and Energy Dispersive X-Ray Spectroscopy (EDX) showing well oriented c-axis growth over the full wafer with slight variation in the film thickness and Sc content over the wafer radius. An overall low density of abnormally oriented grains (AOG) was found. Further wafer mapping for piezoelectric and dielectric properties showed a piezoelectric performance increase by 40 % in comparison to Al$_{0.7}$Sc$_{0.3}$N while only moderately increasing the permittivity and loss factor. Switching measurements revealed ferroelectric behavior of the film on all measured positions with an average remanent polarization of 88.36 uC/cm$^2$ and an average coercive field of 244 V/um. This successful demonstration opens new opportunities for MEMS applications with demands for high forces like microspeakers or quasi static micromirrors. △ Less

Submitted 4 July, 2025; v1 submitted 21 March, 2025; originally announced March 2025.

Comments: Minor revision of manuscript due to Reviewer comments

Interfacial Polarization Switching in Al0.92Sc0.08N/GaN Heterostructures Grown by Sputter Epitaxy

Authors: Niklas Wolff, Georg Schönweger, Redwanul Md. Islam, Ziming Ding, Christian Kübel, Simon Fichtner, Lorenz Kienle

Abstract: The integration of ferroelectric nitride thin films such as Al1-xScxN onto GaN templates could enable enhanced functionality in novel high-power transistors and memory devices. This requires a detailed understanding of the ferroelectric domain structures and their impact on the electric properties. In this contribution, the sputter epitaxy of highly coherent Al0.92Sc0.08N thin films grown on GaN a… ▽ More The integration of ferroelectric nitride thin films such as Al1-xScxN onto GaN templates could enable enhanced functionality in novel high-power transistors and memory devices. This requires a detailed understanding of the ferroelectric domain structures and their impact on the electric properties. In this contribution, the sputter epitaxy of highly coherent Al0.92Sc0.08N thin films grown on GaN approaching lattice-matching conditions is demonstrated. Scanning transmission electron microscopy investigations reveal the formation of polar domains and the mechanism of domain propagation upon ferroelectric switching. Atomic resolution imaging suggests that polarization inversion is initiated by an interfacial switching process in which already the first atomic layer of Al1-xScxN changes its polarization from the as-grown M- to N-polarity. An atomically sharp planar polarization discontinuity is identified at the Al0.92Sc0.08N/GaN interface and described by atomic modeling and chemical structure analysis using electron energy loss spectroscopy, considering local lattice spacings. Moreover, residual domains with M-polarity are identified at the top Pt electrode interface. These insights on the location and the atomic structure of ferroelectric inversion domains in sputter deposited Al1-xScxN/GaN heterostructures will support the development of future non-volatile memory devices and novel HEMT structures based on ferroelectric nitride thin films via interface engineering. △ Less

Submitted 13 February, 2025; originally announced February 2025.

Comments: 14 pages, 7 figures

Site-engineered ferromagnetism in Ca and Cr co-substituted Bismuth Ferrite Nanoparticles

Authors: Mehedi Hasan Prince, Abrar Daiyan, Troyee Mitra Aishi, Anika Rahman Riya, Md. Fakhrul Islam, Md. Abdullah Zubair, Takian Fakhrul

Abstract: Multiferroic perovskites that exhibit room temperature magnetization and polarization have immense potential in the next generation of magneto-electric and spintronic memory devices. In this work, the magnetic and ferroelectric properties of Bismuth Ferrite, BiFeO3 (BFO) nanoparticles (NPs) were enhanced through simultaneous A and B site Ca and Cr co-substitution. Novel compositions of Bi0.97Ca0.0… ▽ More Multiferroic perovskites that exhibit room temperature magnetization and polarization have immense potential in the next generation of magneto-electric and spintronic memory devices. In this work, the magnetic and ferroelectric properties of Bismuth Ferrite, BiFeO3 (BFO) nanoparticles (NPs) were enhanced through simultaneous A and B site Ca and Cr co-substitution. Novel compositions of Bi0.97Ca0.03CrxFe1-xO3 (x=0, 0.01, 0.03, 0.05) were synthesized using the sol-gel route and annealed at 550 degrees Celcius. Rietveld Refinement of XRD patterns confirmed high phase purity, while SEM analysis revealed a decreasing trend in average particle size with increasing dopant concentration. Hysteresis loops showed enhanced magnetic properties as particle size approached the spin cycloid wavelength (around 62 nm), disrupting the intrinsic antiferromagnetic ordering of BFO. Moreover, the presence of exchange bias in the NPs was linked to the formation of core-shell structure. Temperature dependent magnetization studies showed an increase in Néel temperature upon Ca substitution. XPS analysis confirmed that Bi0.97Ca0.03FeO3 samples exhibited the highest oxygen vacancy concentration, while Fe3+ remained the dominant oxidation state across all compositions. Ferroelectric polarization loop measurements showed enhanced remanent polarization in doped samples, with leakage linked to oxygen vacancies and extrinsic microstructural effects. △ Less

Submitted 6 February, 2025; originally announced February 2025.

Comments: Mehedi Hasan Prince, Abrar Daiyan, Troyee Mitra Aishi contributed equally to this work. Paper undergoing review in Ceramics International

Investigation of magnetic ordering with spin reorientation transition and optical properties in Dy$_2$CoCrO$_6$ nanomaterials

Authors: M. M. Islam, M. A. Islam, Rana Hossain, M. J. Hosen, M. D. I. Bhuyan

Abstract: This study reports the synthesis and physical properties of polycrystalline Dy$_2$CoCrO$_6$ (DCCO) nanoparticles. Analysis of the powder X-ray diffraction (XRD) pattern using Rietveld refinement showed that the compound crystallizes in an orthorhombic crystal structure with a space group Pbnm. The particle size of approximately 57 nm was confirmed through micrographs obtained from field emission s… ▽ More This study reports the synthesis and physical properties of polycrystalline Dy$_2$CoCrO$_6$ (DCCO) nanoparticles. Analysis of the powder X-ray diffraction (XRD) pattern using Rietveld refinement showed that the compound crystallizes in an orthorhombic crystal structure with a space group Pbnm. The particle size of approximately 57 nm was confirmed through micrographs obtained from field emission scanning electron microscopy and transmission electron microscopy. The X-ray photoelectron spectroscopy (XPS) investigations identified a mixed-valence state of Co and Cr cations. Magnetic susceptibility data indicated Curie-Weiss behavior in the temperature range 140-340 K and the onset of antiferromagnetic interactions with a Neel temperature of 119 K. At 31 K, DCCO shows spin reorientation transition from $Γ_4$(G$_x$A$_y$F$_z$) to $Γ_2$(F$_x$C$_y$G$_z$). Furthermore, room-temperature magnetization measurements demonstrated the antiferromagnetic behavior with weak ferromagnetic interactions at low temperatures. Additionally, DCCO exhibited semiconducting behavior with a direct optical bandgap of 1.97 eV, indicating promise for visible-light-driven energy harvesting and catalytic applications. △ Less

Submitted 2 June, 2025; v1 submitted 5 January, 2025; originally announced January 2025.

Journal ref: Physica B: Condensed Matter Volume 692, 1 November 2024, 416368

DFT based comparative analysis of physical properties of binary metallic diborides XB$_2$ (X = Cr, Mo and W)

Authors: Razu Ahmed, Md. Sohel Rana, Md. Sajidul Islam, S. H. Naqib

Abstract: Transition-metal borides (TMBs) have long attracted attention of the researchers because of their unique mechanical and electrical properties including superconductivity. We have explored the structural, mechanical, electronic, optical, and some thermophysical properties of XB$_2$ (X = Cr, Mo and W) binary metallic diborides in detail employing density functional theory based first-principles meth… ▽ More Transition-metal borides (TMBs) have long attracted attention of the researchers because of their unique mechanical and electrical properties including superconductivity. We have explored the structural, mechanical, electronic, optical, and some thermophysical properties of XB$_2$ (X = Cr, Mo and W) binary metallic diborides in detail employing density functional theory based first-principles method. Many of the physical properties, including direction-dependent mechanical properties, optical properties, and thermo-mechanical properties are being investigated for the first time. △ Less

Submitted 27 December, 2024; originally announced December 2024.

Effect of Grain Size and Local Chemical Order on Creep Resistance in MoNbTaW Refractory High-Entropy Alloy: A Molecular Dynamics Study

Authors: Saifuddin Zafar, Mashaekh Tausif Ehsan, Sourav Das Suvro, Mahmudul Islam, Mohammad Nasim Hasan

Abstract: Refractory high-entropy alloy (RHEA) is a promising class of materials with potential applications in extreme environments, where the dominant failure mode is thermal creep. The design of these alloys, therefore, requires an understanding of how their microstructure and local chemical distribution affect creep behavior. In this study, we performed high-fidelity atomistic simulations using machine-… ▽ More Refractory high-entropy alloy (RHEA) is a promising class of materials with potential applications in extreme environments, where the dominant failure mode is thermal creep. The design of these alloys, therefore, requires an understanding of how their microstructure and local chemical distribution affect creep behavior. In this study, we performed high-fidelity atomistic simulations using machine-learning interatomic potentials to explore the creep deformation of MoNbTaW RHEA under a wide range of stress and temperature conditions. We parametrized grain size and local chemical order (LCO) to investigate the effects of these two important design variables, which can be controlled during the alloy fabrication process, on creep deformation process. Our investigation revealed that resistance to creep deformation is enhanced with larger grain size due to the reduced grain boundary area, which limits grain-boundary dominated deformation mechanisms such as Coble creep and grain boundary sliding. Introducing LCO in the microstructure has the same effect of increasing resistance to creep deformation by strengthening grain boundary. This study highlights the importance of utilizing LCO in conjunction with other microstructural properties when designing RHEAs for extreme environmental applications. △ Less

Submitted 26 March, 2026; v1 submitted 30 November, 2024; originally announced December 2024.

Comments: 23 pages, 6 figures

Improved Leakage Currents and Polarity Control through Oxygen Incorporation in Ferroelectric Al0.73Sc0.27N Thin Films

Authors: Md Redwanul Islam, Niklas Wolff, Georg Schönweger, Tom-Niklas Kreutzer, Margaret Brown, Maike Gremmel, Patrik Straňák, Lutz Kirste, Geoff L. Brennecka, Simon Fichtner, Lorenz Kienle

Abstract: This article examines systematic oxygen (O)-incorporation to reduce total leakage currents in sputtered wurtzite-type ferroelectric Al0.73Sc0.27N thin films, along with its impact on the material structure and the polarity of the as-grown films. The O in the bulk Al0.73Sc0.27N was introduced through an external gas source during the reactive sputter process. In comparison to samples without doping… ▽ More This article examines systematic oxygen (O)-incorporation to reduce total leakage currents in sputtered wurtzite-type ferroelectric Al0.73Sc0.27N thin films, along with its impact on the material structure and the polarity of the as-grown films. The O in the bulk Al0.73Sc0.27N was introduced through an external gas source during the reactive sputter process. In comparison to samples without doping, O-doped films showed almost a fourfold reduction of the leakage current near the coercive field. In addition, doping resulted in the reduction of the steady-state leakage currents by roughly one order of magnitude sub-coercive fields. Microstructure analysis using X-ray diffraction 1and scanning transmission electron microscopy (STEM) revealed no significant structural degradation of the bulk Al0.73Sc0.27N. In case of the maximum O-doped film, the c-axis out-of-plane texture increased by only 20% from 1.8° and chemical mapping revealed a uniform distribution of oxygen incorporation into the bulk. Our results further demonstrate the ability to control the as-deposited polarity of Al0.73Sc0.27N via the O-concentration, changing from nitrogen- to metal-polar orientation. Thus, this article presents a promising approach to mitigate the leakage current in wurtzite-type Al0.73Sc0.27N without incurring any significant structural degradation of the bulk thin film quality, thereby making ferroelectric nitrides more suitable for microelectronic applications. △ Less

Submitted 26 November, 2024; originally announced November 2024.

Robust coherent dynamics of homogeneously limited anisotropic excitons in two-dimensional layered ReS2

Authors: Rup Kumar Chowdhury, Md Samiul Islam, Marie Barthelemy, Nicolas Beyer, Lorry Engel, Jean-Sebastien Pelle, Mircea Rastei, Alberto Barsella, Francois Fras

Abstract: The discovery of in-plane anisotropic excitons in two-dimensional layered semiconductors enables state-of-the-art nanophotonic applications. A fundamental yet unknown parameter of these quasiparticles is the coherence time (T_2 ), which governs the quantum dephasing timescale, over which the coherent superposition of excitons can be maintained and manipulated. Here, we report the direct measuremen… ▽ More The discovery of in-plane anisotropic excitons in two-dimensional layered semiconductors enables state-of-the-art nanophotonic applications. A fundamental yet unknown parameter of these quasiparticles is the coherence time (T_2 ), which governs the quantum dephasing timescale, over which the coherent superposition of excitons can be maintained and manipulated. Here, we report the direct measurement of T_2 within the sub-picosecond range, along with multiple population decay timescales (T_1 ) at resonance for anisotropic excitons in pristine layered rhenium disulfide (ReS2). We observe a notable weak dependence on layer thickness for T_2 , and a quasi-independence for T_1 . The excitonic coherence in few-layer ReS2 exhibits exceptional robustness against optical density and temperature compared to other two-dimensional semiconductors, enabling quantum features even at room temperature. No photon echo fingerprints were observed in pristine ReS2, highlighting the homogeneous character of the anisotropic excitonic transitions and a particularly low level of disorder in exfoliated flakes. Lastly, our results for mono- to bulk-like ReS2 support a direct gap band structure regardless their layer thickness, addressing the ongoing discussion about its nature. △ Less

Submitted 20 November, 2024; originally announced November 2024.

12-spin-qubit arrays fabricated on a 300 mm semiconductor manufacturing line

Authors: Hubert C. George, Mateusz T. Mądzik, Eric M. Henry, Andrew J. Wagner, Mohammad M. Islam, Felix Borjans, Elliot J. Connors, J. Corrigan, Matthew Curry, Michael K. Harper, Daniel Keith, Lester Lampert, Florian Luthi, Fahd A. Mohiyaddin, Sandra Murcia, Rohit Nair, Rambert Nahm, Aditi Nethwewala, Samuel Neyens, Bishnu Patra, Roy D. Raharjo, Carly Rogan, Rostyslav Savytskyy, Thomas F. Watson, Josh Ziegler , et al. (7 additional authors not shown)

Abstract: Intels efforts to build a practical quantum computer are focused on developing a scalable spin-qubit platform leveraging industrial high-volume semiconductor manufacturing expertise and 300 mm fabrication infrastructure. Here, we provide an overview of the design, fabrication, and demonstration of a new customized quantum test chip, which contains 12-quantum-dot spin-qubit linear arrays, code name… ▽ More Intels efforts to build a practical quantum computer are focused on developing a scalable spin-qubit platform leveraging industrial high-volume semiconductor manufacturing expertise and 300 mm fabrication infrastructure. Here, we provide an overview of the design, fabrication, and demonstration of a new customized quantum test chip, which contains 12-quantum-dot spin-qubit linear arrays, code named Tunnel Falls. These devices are fabricated using immersion and extreme ultraviolet lithography (EUV), along with other standard high-volume manufacturing (HVM) processes, as well as production-level process control. We present key device features and fabrication details, as well as qubit characterization results confirming device functionality. These results corroborate our fabrication methods and are a crucial step towards scaling of extensible 2D qubit array schemes. △ Less

Submitted 20 December, 2024; v1 submitted 21 October, 2024; originally announced October 2024.

Conductance properties of an $α$-$T_3$ Corbino disk

Authors: Mijanur Islam, Saurabh Basu

Abstract: In this work, we investigate an $α$-$T_3$ lattice in the form of a Corbino disk, characterized by inner and outer radii $R_1$ and $R_2$, threaded by a tunable magnetic flux. Through exact (analytic) solution of the stationary Dirac-Weyl equation, we compute the transmission probability of the carriers and hence obtain the conductance features for $0<α\leq 1$ ($α$ denotes the strength of the hoppin… ▽ More In this work, we investigate an $α$-$T_3$ lattice in the form of a Corbino disk, characterized by inner and outer radii $R_1$ and $R_2$, threaded by a tunable magnetic flux. Through exact (analytic) solution of the stationary Dirac-Weyl equation, we compute the transmission probability of the carriers and hence obtain the conductance features for $0<α\leq 1$ ($α$ denotes the strength of the hopping between the central atom and one of the other two) which allows ascertaining the role of the flat band, alongwith scrutinizing the transport features from graphene to a dice lattice. Our results reveal periodic Aharonov-Bohm (AB) oscillations in the conductance, reminiscent of the utility of the Corbino disk as an electron pump. Further, these results are strongly influenced by parameters, such as, doping level, ratio of the inner and outer radii, magnetic flux, and $α$. Additionally, complex quantum interference effect resulting in the possible emergence of higher harmonic modes and split-peak structures in the conductance, become prominent for smaller $α$ values and larger ratios of the radii. We also find that, away from the charge-neutrality point (zero doping), the conductance oscillations are more pronounced and sensitive to the various parameters, with the corresponding behaviour largely governed via the evanescent wave transport. The Fano factor reveals distinct transport regimes, transitioning from Poissonian to pseudo-diffusive for $α< 1$, and from ballistic to pseudo-diffusive for $α= 1$. This setup, thus serves as a fertile ground for studying the generation of quantum Hall current and Aharonov-Bohm (AB) oscillations in a flat band system, alongwith demonstrating intricate appearance of higher harmonics in electron transport. △ Less

Submitted 18 April, 2025; v1 submitted 30 September, 2024; originally announced September 2024.

Comments: 10 pages, 11 figures, comments are welcome

Nonequilibrium chemical short-range order in metallic alloys

Authors: Mahmudul Islam, Killian Sheriff, Yifan Cao, Rodrigo Freitas

Abstract: Metallic alloys are routinely subjected to nonequilibrium processes during manufacturing, such as rapid solidification and thermomechanical processing. It has been suggested in the high-entropy alloy literature that chemical short-range order (SRO) could offer a new knob to tailor materials properties. While evidence of the effect of SRO on materials properties accumulates, the state of SRO evolut… ▽ More Metallic alloys are routinely subjected to nonequilibrium processes during manufacturing, such as rapid solidification and thermomechanical processing. It has been suggested in the high-entropy alloy literature that chemical short-range order (SRO) could offer a new knob to tailor materials properties. While evidence of the effect of SRO on materials properties accumulates, the state of SRO evolution during alloy manufacturing remains obscure. Here, we employ high-fidelity atomistic simulations to track SRO evolution during the solidification and thermomechanical processing of alloys. Our investigation reveals that alloy processing can lead to nonequilibrium steady-states of SRO that are different from any equilibrium state. The mechanism behind nonequilibrium SRO formation is shown to be an inherent ordering bias present in nonequilibrium events. These results demonstrate that conventional manufacturing processes provide pathways for tuning SRO that lead to a broad nonequilibrium spectrum of SRO states beyond the equilibrium design space of alloys. △ Less

Submitted 9 October, 2025; v1 submitted 23 September, 2024; originally announced September 2024.

Comments: 17 pages, 4 figures

Journal ref: Nat Commun 16, 8926 (2025)

Electronic vs. phononic thermal transport in Cr-doped V2O3 thin films across the Mott transition

Authors: Johannes Mohr, Kiumars Aryana, Md. Rafiqul Islam, Dirk J. Wouters, Rainer Waser, Patrick E. Hopkins, Joyeeta Nag, Daniel Bedau

Abstract: Understanding the thermal conductivity of chromium doped V2O3 is crucial for optimizing the design of selectors for memory and neuromorphic devices. We utilized the time-domain thermoreflectance technique to measure the thermal conductivity of chromium doped V2O3 across varying concentrations, spanning the doping induced metal-insulator transition. In addition, different oxygen stoichiometries and… ▽ More Understanding the thermal conductivity of chromium doped V2O3 is crucial for optimizing the design of selectors for memory and neuromorphic devices. We utilized the time-domain thermoreflectance technique to measure the thermal conductivity of chromium doped V2O3 across varying concentrations, spanning the doping induced metal-insulator transition. In addition, different oxygen stoichiometries and film thicknesses were investigated in their crystalline and amorphous phases. Chromium doping concentration (0%-30%) and the degree of crystallinity emerged as the predominant factors influencing the thermal properties, while the effect of oxygen flow (600-1400 ppm) during deposition proved to be negligible. Our observations indicate that even in the metallic phase of V2O3, the lattice contribution is the dominant factor in thermal transport with no observable impact from the electrons on heat transport. Finally, the thermal conductivity of both amorphous and crystalline V2O3 was measured at cryogenic temperatures (80-450 K). Our thermal conductivity measurements as a function of temperature reveal that both phases exhibit behavior similar to amorphous materials, indicating pronounced phonon scattering effects in the crystalline phase of V2O3. △ Less

Submitted 16 September, 2024; originally announced September 2024.

Comments: Submitted to APL

Holstein polaron in a pseudospin-$1$ quantum spin Hall system: first and second order topological phase transitions

Authors: Kuntal Bhattacharyya, Srijata Lahiri, Mijanur Islam, Saurabh Basu

Abstract: We theoretically propose the occurrence of a quantum spin Hall (QSH) and a second order topological phase transition (TPT) driven by electron-phonon (e-p) coupling in a pseudospin-$1$ fermionic system on an $α$-$T_3$ lattice. Our model is formulated in the spirit of the Kane-Mele model modified by the Holstein Hamiltonian. The Lang-Firsov approach is employed to describe polarons reasonably well i… ▽ More We theoretically propose the occurrence of a quantum spin Hall (QSH) and a second order topological phase transition (TPT) driven by electron-phonon (e-p) coupling in a pseudospin-$1$ fermionic system on an $α$-$T_3$ lattice. Our model is formulated in the spirit of the Kane-Mele model modified by the Holstein Hamiltonian. The Lang-Firsov approach is employed to describe polarons reasonably well in the anti-adiabatic (high frequency) limit and to obtain an effective electronic Hamiltonian. It is shown that the system possesses topologically nontrivial phases up to a critical e-p coupling, $λ_c$ and are characterized by the helical QSH edge states along with a non-zero $\mathbb{Z}_2$ invariant for a certain range of $α$. The topological phase vanishes beyond $λ_c$ and is accompanied by a bulk gap closing transition at $λ_c$, manifesting a TPT. We observe a more intriguing phenomenon for higher values of $α$, where the system exhibits TPTs supported by two distinct gap closing transitions at $λ_{c_1}$ and $λ_{c_2}$, while a slim region at slightly lower values hosts a semi-metallic signature below $λ_{c_1}$. Subsequently, to explore more intricate features, we introduce a time reversal symmetry breaking magnetic field to trigger the formation of a second order topological phase. The magnetic field, by construction causes a boundary dependent gapping out of the edge states, consequently giving rise to robust corner modes in a tailored open boundary conditions. We justify the formation of the higher order phase by employing an appropriate invariant, namely the projected spin Chern number. Finally, we show that the e-p coupling significantly influences the corner modes (and also the real space energy bandstructure), corroborating a higher order TPT as we tune $λ$ beyond a critical value for a given value of $α$. △ Less

Submitted 26 August, 2024; originally announced August 2024.

Comments: 18 pages, 18 figures. Comments are welcome

Journal ref: Phys. Rev. B 110, 235432 (2024)

Growth of Ba_2CoWO_6 Single Crystals and their Magnetic, Thermodynamic and Electronic Properties

Authors: Abanoub R. N. Hanna, A. T. M. N. Islam, C. Ritter, S. Luther, R. Feyerherm, B. Lake

Abstract: This study explores the bulk crystal growth, structural characterization, and physical property measurements of the cubic double perovskite Ba_2CoWO_6(BCWO). In BCWO, Co+2 ions form a face-centered cubic (FCC) lattice with non-distorted cobalt octahedra. The compound exhibits long-range antiferromagnetic order below TN = 14 K. Magnetization data indicated a slight anisotropy along with a spin-flop… ▽ More This study explores the bulk crystal growth, structural characterization, and physical property measurements of the cubic double perovskite Ba_2CoWO_6(BCWO). In BCWO, Co+2 ions form a face-centered cubic (FCC) lattice with non-distorted cobalt octahedra. The compound exhibits long-range antiferromagnetic order below TN = 14 K. Magnetization data indicated a slight anisotropy along with a spin-flop transition at 10 kOe , a saturation field of 310 kOe and an ordered moment of 2.17 Mu_B at T = 1.6 K. Heat capacity measurements indicate an effective j = 1/2 ground state configuration, resulting from the combined effects of the crystal electric field and spin-orbit interaction. Surface photovoltage analysis reveals two optical gaps in the UV-Visible region, suggesting potential applications in photocatalysis and photovoltaics. The magnetic and optical properties highlight the significant role of orbital contributions within BCWO, indicating various other potential applications. △ Less

Submitted 16 August, 2024; originally announced August 2024.

Comments: 15 pages, 7 figures

Harnessing Ferro-Valleytricity in Penta-Layer Rhombohedral Graphene for Memory and Compute

Authors: Md Mazharul Islam, Shamiul Alam, Md Rahatul Islam Udoy, Md Shafayat Hossain, Kathleen E Hamilton, Ahmedullah Aziz

Abstract: Two-dimensional materials with multiple degrees of freedom, including spin, valleys, and orbitals, open up an exciting avenue for engineering multifunctional devices. Beyond spintronics, these degrees of freedom can lead to novel quantum effects such as valley-dependent Hall effects and orbital magnetism, which could revolutionize next-generation electronics. However, achieving independent control… ▽ More Two-dimensional materials with multiple degrees of freedom, including spin, valleys, and orbitals, open up an exciting avenue for engineering multifunctional devices. Beyond spintronics, these degrees of freedom can lead to novel quantum effects such as valley-dependent Hall effects and orbital magnetism, which could revolutionize next-generation electronics. However, achieving independent control over valley polarization and orbital magnetism has been a challenge due to the need for large electric fields. A recent breakthrough involving penta-layer rhombohedral graphene has demonstrated the ability to individually manipulate anomalous Hall signals and orbital magnetic hysteresis, forming what is known as a valley-magnetic quartet. Here, we leverage the electrically tunable Ferro-valleytricity of penta-layer rhombohedral graphene to develop non-volatile memory and in-memory computation applications. We propose an architecture for a dense, scalable, and selector-less non-volatile memory array that harnesses the electrically tunable ferro-valleytricity. In our designed array architecture, non-destructive read and write operations are conducted by sensing the valley state through two different pairs of terminals, allowing for independent optimization of read/write peripheral circuits. The power consumption of our PRG-based array is remarkably low, with only ~ 6 nW required per write operation and ~ 2.3 nW per read operation per cell. This consumption is orders of magnitude lower than that of the majority of state-of-the-art cryogenic memories. Additionally, we engineer in-memory computation by implementing majority logic operations within our proposed non-volatile memory array without modifying the peripheral circuitry. Our framework presents a promising pathway toward achieving ultra-dense cryogenic memory and in-memory computation capabilities. △ Less

Submitted 2 August, 2024; originally announced August 2024.

Low dimensional fragment-based descriptors for property predictions in inorganic materials with machine learning

Authors: Md Mohaiminul Islam

Abstract: In recent times, the use of machine learning in materials design and discovery has aided to accelerate the discovery of innovative materials with extraordinary properties, which otherwise would have been driven by a laborious and time-consuming trial-and-error process. In this study, a simple yet powerful fragment-based descriptor, Low Dimensional Fragment Descriptors (LDFD), is proposed to work i… ▽ More In recent times, the use of machine learning in materials design and discovery has aided to accelerate the discovery of innovative materials with extraordinary properties, which otherwise would have been driven by a laborious and time-consuming trial-and-error process. In this study, a simple yet powerful fragment-based descriptor, Low Dimensional Fragment Descriptors (LDFD), is proposed to work in conjunction with machine learning models to predict important properties of a wide range of inorganic materials such as perovskite oxides, metal halide perovskites, alloys, semiconductor, and other materials system and can also be extended to work with interfaces. To predict properties, the generation of descriptors requires only the structural formula of the materials and, in presence of identical structure in the dataset, additional system properties as input. And the generation of descriptors involves few steps, encoding the formula in binary space and reduction of dimensionality, allowing easy implementation and prediction. To evaluate descriptor performance, six known datasets with up to eight components were compared. The method was applied to properties such as band gaps of perovskites and semiconductors, lattice constant of magnetic alloys, bulk/shear modulus of superhard alloys, critical temperature of superconductors, formation enthalpy and energy above hull convex of perovskite oxides. An advanced python-based data mining tool matminer was utilized for the collection of data. The prediction accuracies are equivalent to the quality of the training data and show comparable effectiveness as previous studies. This method should be extendable to any inorganic material systems which can be subdivided into layers or crystal structures with more than one atom site, and with the progress of data mining the performance should get better with larger and unbiased datasets. △ Less

Submitted 30 July, 2024; originally announced July 2024.

Comments: Work in progress

Electron-phonon coupling induced topological phase transition in an $α$-$T_{3}$ Haldane-Holstein model

Authors: Mijanur Islam, Kuntal Bhattacharyya, Saurabh Basu

Abstract: We present impelling evidence of topological phase transitions induced by electron-phonon (e-ph) coupling in an $α$-$T_3$ Haldane-Holstein model that presents smooth tunability between graphene ($α=0$) and a dice lattice $(α=1)$. The e-ph coupling has been incorporated via the Lang-Firsov transformation which adequately captures the polaron physics in the high frequency (anti-adiabatic) regime, an… ▽ More We present impelling evidence of topological phase transitions induced by electron-phonon (e-ph) coupling in an $α$-$T_3$ Haldane-Holstein model that presents smooth tunability between graphene ($α=0$) and a dice lattice $(α=1)$. The e-ph coupling has been incorporated via the Lang-Firsov transformation which adequately captures the polaron physics in the high frequency (anti-adiabatic) regime, and yields an effective Hamiltonian of the system through zero phonon averaging at $T=0$. While exploring the signature of the phase transition driven by polaron and its interplay with the parameter $α$, we identify two regions based on the values of $α$, namely, the low to intermediate range $(0 < α\le 0.6)$ and larger values of $α~(0.6 < α< 1)$ where the topological transitions show distinct behaviour. There exists a single critical e-ph coupling strength for the former, below which the system behaves as a topological insulator characterized by edge modes, finite Chern number, and Hall conductivity, with all of them vanishing above this value, and the system undergoes a spectral gap closing transition. Further, the critical coupling strength depends upon $α$. For the latter case $(0.6 < α< 1)$, the scenario is more interesting where there are two critical values of the e-ph coupling at which trivial-topological-trivial and topological-topological-trivial phase transitions occur for $α$ in the range $[0.6:1]$. Our studies on e-ph coupling induced phase transitions show a significant difference with regard to the well-known unique transition occurring at $α= 0.5$ (or at $0.7$) in the absence of the e-ph coupling, and thus underscore the importance of interaction effects on the topological phase transitions. △ Less

Submitted 19 April, 2024; v1 submitted 12 April, 2024; originally announced April 2024.

Comments: 18 pages, 16 figures, comments are welcome

Non-collinear first-principles studies of the spin-electric coupling in frustrated triangular molecular magnets

Authors: M. F. Islam, Kushantha P. K. Withanage, C. M. Canali, Mark R. Pederson

Abstract: Frustrated triangular molecular magnets (MMs) with anti-ferromagnetic ground states (GS) are an important class of magnetic systems with potential applications in quantum information processing. The two-fold degenerate GS of these molecules, characterized by spin chirality, can be utilized to encode qubits for quantum computing. Furthermore, because of the lack of inversion symmetry in these molec… ▽ More Frustrated triangular molecular magnets (MMs) with anti-ferromagnetic ground states (GS) are an important class of magnetic systems with potential applications in quantum information processing. The two-fold degenerate GS of these molecules, characterized by spin chirality, can be utilized to encode qubits for quantum computing. Furthermore, because of the lack of inversion symmetry in these molecules, an electric field couples directly states of opposite chirality, allowing a very efficient and fast control of the qubits. In this work we present a theoretical method to calculate the spin-electric coupling for triangular MMs with effective {\it local} spins $s$ larger than 1/2, which is amenable to a first-principles implementation based on density functional theory (DFT). In contrast to MMs where the net magnetization at the magnetic atoms is $μ_{\rm B}/2$ ($μ_{\rm B} $ is the Bohr magneton), the DFT treatment of frustrated triangular MMs with larger local magnetizations requires a fully non-collinear approach, which we have implemented in the NRLMOL DFT code. As an example, we have used these methods to evaluate the spin-electric coupling for a spin $s = 5/2$ $\{\mathrm{Fe_3}\}$ triangular MM, where this effect has been observed experimentally for the first time quite recently. Our theoretical and computational methods will help elucidate and further guide ongoing experimental work in the field of quantum molecular spintronics. △ Less

Submitted 16 February, 2024; originally announced February 2024.

Comments: 9 pages, 6 figures

Journal ref: Phys. Rev. B 109, 214407, 2024

Field-free ultrafast magnetization reversal of a nanodevice by a chirped current pulse via spin-orbit torque

Authors: Y. D. Liu, M. T. Islam, T. Min, X. S. Wang, X. R. Wang

Abstract: We investigated the magnetization reversal of a perpendicularly magnetized nanodevice using a chirped current pulse (CCP) via spin-orbit torques (SOT). Our findings demonstrate that both the field-like (FL) and damping-like (DL) components of SOT in CCP can efficiently induce ultrafast magnetization reversal without any symmetry-breaking means. For a wide frequency range of the CCP, the minimal cu… ▽ More We investigated the magnetization reversal of a perpendicularly magnetized nanodevice using a chirped current pulse (CCP) via spin-orbit torques (SOT). Our findings demonstrate that both the field-like (FL) and damping-like (DL) components of SOT in CCP can efficiently induce ultrafast magnetization reversal without any symmetry-breaking means. For a wide frequency range of the CCP, the minimal current density obtained is significantly smaller compared to the current density of conventional SOT-reversal. This ultrafast reversal is due to the CCP triggering enhanced energy absorption (emission) of the magnetization from (to) the FL- and DL-components of SOT before (after) crossing over the energy barrier. We also verified the robustness of the CCP-driven magnetization reversal at room temperature. Moreover, this strategy can be extended to switch the magnetic states of perpendicular synthetic antiferromagnetic (SAF) and ferrimagnetic (SFi) nanodevices. Therefore, these studies enrich the basic understanding of field-free SOT-reversal and provide a novel way to realize ultrafast SOT-MRAM devices with various free layer designs: ferromagnetic, SAF, and SFi. △ Less

Submitted 12 January, 2024; v1 submitted 9 January, 2024; originally announced January 2024.

Comments: 9 pages, 7 figures