Showing 1–31 of 31 results for author: Shah, M

Floquet Engineering of Topological Phases and Magneto-Optical Response in a Driven $d$-wave Altermagnet

Authors: Muzamil Shah

Abstract: We study how Floquet driving with linearly polarized light controls the topology and magneto-optical response of a two-dimensional (2D) $d$-wave altermagnet. In the absence of linearly polarized optical field and under spin conservation, we find that the system hosts a spin-Chern (a quantum-spin-Hall analog) phase with Chern numbers of opposite sign in the two spin sectors. The irradiated optical… ▽ More We study how Floquet driving with linearly polarized light controls the topology and magneto-optical response of a two-dimensional (2D) $d$-wave altermagnet. In the absence of linearly polarized optical field and under spin conservation, we find that the system hosts a spin-Chern (a quantum-spin-Hall analog) phase with Chern numbers of opposite sign in the two spin sectors. The irradiated optical field breaks the $C_{4z}\mathcal{T}$ crystalline antiunitary symmetry between the spin sectors. Symmetry breaking originates from polarization-dependent Peierls phases, which renormalize hopping anisotropically along the two axes. The resulting spin-selective gap closures produce intermediate Chern-insulating phases with $C=\pm1$. The drive amplitude $A_0$ determines the inversion thresholds, while rotating the polarization by $π/2$ swaps the spin sectors and reverses the Chern number. Using the Kubo formalism, we compute the frequency-dependent longitudinal and Hall conductivities and derive the corresponding Faraday and Kerr rotations for a free-standing conducting sheet. The longitudinal response tracks the Floquet-renormalized interband thresholds, whereas the optical Hall response, together with the sign of the magneto-optical rotations, distinguishes the two opposite Berry-curvature chiralities. Sizable Kerr angles occur only within narrow resonant windows and should be interpreted together with the reflected intensity and Kerr ellipticity. These results identify linearly polarized light as a symmetry-selective handle for spin-resolved band inversion, Chern-number switching, and contact-free optical detection in $d$-wave altermagnets. △ Less

Submitted 11 August, 2026; originally announced August 2026.

High-pressure electride superconductor Li5N for multifunctional applications: A theoretical insight into the physical properties

Authors: M. Abdul Hadi Shah, S. H. Naqib

Abstract: This study aims to unveil the physical properties of multifunctional Li5N electride under high pressure in the range of 150-350 GPa through first principles analysis within the density functional theory. This study aims to unveil the physical properties of multifunctional Li5N electride under high pressure in the range of 150-350 GPa through first principles analysis within the density functional theory. △ Less

Submitted 11 August, 2026; originally announced August 2026.

Nonlinear Hall effect in Floquet-driven monolayer 1T$'$-MoS$_2$

Authors: Muhammad Faisal, Muzamil Shah, Imtiaz Khan, Reza Asgari

Abstract: We study the nonlinear Hall effect in Floquet-driven monolayer \(1T'\)-MoS\(_2\), a low-symmetry quantum spin Hall material whose tilted Dirac bands sustain an intrinsic Berry-curvature dipole without the need for strain or trigonal warping. We show that off-resonant circularly polarized light offers a way to control both the sign and the magnitude of the nonlinear Hall response through optically… ▽ More We study the nonlinear Hall effect in Floquet-driven monolayer \(1T'\)-MoS\(_2\), a low-symmetry quantum spin Hall material whose tilted Dirac bands sustain an intrinsic Berry-curvature dipole without the need for strain or trigonal warping. We show that off-resonant circularly polarized light offers a way to control both the sign and the magnitude of the nonlinear Hall response through optically induced topological phase transitions using a Floquet effective Hamiltonian and nonlinear semiclassical transport theory. We show that the anisotropic crystal symmetry enforces a selection rule in which the Berry-curvature dipole elements satisfy $D_x\equiv0$, while a finite $D_y$ originates from the intrinsic band tilt. The Berry curvature is recreated in momentum space as the Floquet drive successively inverts individual spin-valley sectors, resulting in an identical sign reversal of the nonlinear Hall conductivity and the Berry-curvature dipole at each bulk gap closing. In contrast, tuning the band tilt modifies only the magnitude of the response without changing its sign, establishing the observed sign reversal as an unambiguous transport signature of genuine Floquet topological phase transitions. We further show that the nonlinear Hall response can be controlled by the driving strength, perpendicular electric field, Fermi energy, and temperature, providing multiple experimental knobs for observation. Our findings establish the sign of the nonlinear Hall response as a universal transport fingerprint of Floquet-engineered topology and point to monolayer \(1T'\)-MoS\(_2\) as a viable platform for all-electrical detection of nonequilibrium topological phases. △ Less

Submitted 4 July, 2026; originally announced July 2026.

Intrinsic Topological Control of the Orbital Hall Effect in Buckled Dirac Materials

Authors: Madiha Zia, Muzamil Shah, Kashif Sabeeh, Gao Xianlong, Reza Asgari

Abstract: We study the orbital Hall response in buckled two-dimensional Dirac materials using a unified framework that includes an antiferromagnetic exchange field, a perpendicular electric field, and intrinsic spin-orbit coupling. We show that the orbital Hall conductivity is considerably boosted around band-inversion points and shows different signatures across multiple electronic phases using a low-energ… ▽ More We study the orbital Hall response in buckled two-dimensional Dirac materials using a unified framework that includes an antiferromagnetic exchange field, a perpendicular electric field, and intrinsic spin-orbit coupling. We show that the orbital Hall conductivity is considerably boosted around band-inversion points and shows different signatures across multiple electronic phases using a low-energy massive Dirac model in conjunction with Berry-curvature-based linear response theory. We find a series of quantum spin Hall, valley Hall, and anomalous Hall regimes by methodically adjusting external fields, and demonstrate how the evolution of the orbital response is controlled by the redistribution of Berry curvature between spin and valley sectors. We examine the impacts of finite temperature in more detail and find that although the response s size is suppressed by thermal broadening, the distinctive phase-dependent features remain robust. Our findings demonstrate that orbital Hall conductivity offers a sensitive band topology probe in Dirac systems and emphasize buckled two-dimensional materials as a flexible platform for engineering tunable orbital currents for orbitronic applications. △ Less

Submitted 24 May, 2026; originally announced May 2026.

Physical properties of transition metal hydride superconductors Mg2TmH6 (Tm = Rh, Pd, Ir, Pt) by first-principles calculations

Authors: Md Ashraful Alam, Md Abdul Hadi Shah, F. Parvin, S. H. Naqib

Abstract: In this work, a comprehensive first-principles investigation of the structural, hydrogen storage potential, electronic, elastic, mechanical, thermophysical, superconducting, and optical properties of Mg2TmH6 (Tm = Rh, Pd, Ir, Pt) hydrides is presented. Obtained results demonstrate that Mg2TmH6 hydrides combine favorable hydrogen storage, mechanical robustness, superconductivity, and multifunctiona… ▽ More In this work, a comprehensive first-principles investigation of the structural, hydrogen storage potential, electronic, elastic, mechanical, thermophysical, superconducting, and optical properties of Mg2TmH6 (Tm = Rh, Pd, Ir, Pt) hydrides is presented. Obtained results demonstrate that Mg2TmH6 hydrides combine favorable hydrogen storage, mechanical robustness, superconductivity, and multifunctional optical properties, making them promising candidates for energy storage, superconducting and advanced optoelectronic applications. △ Less

Submitted 28 April, 2026; originally announced April 2026.

Light-Induced Topological Phase Transitions and Anomalous Thermal Transport in d-Wave Altermagnets

Authors: Ayesha Maryam, Muzamil Shah, Kashif Sabeeh, Reza Asgari

Abstract: We study intrinsic thermal transport and Floquet-engineered topology in a two-dimensional d wave altermagnetic topological insulator powered by linearly polarized light. We analyze the anomalous Hall, Nernst, and thermal Hall conductivities, as well as their spin-resolved equivalents, and develop closed-form formulas for the Berry curvature using an analytically calculated high-frequency effective… ▽ More We study intrinsic thermal transport and Floquet-engineered topology in a two-dimensional d wave altermagnetic topological insulator powered by linearly polarized light. We analyze the anomalous Hall, Nernst, and thermal Hall conductivities, as well as their spin-resolved equivalents, and develop closed-form formulas for the Berry curvature using an analytically calculated high-frequency effective Hamiltonian. We demonstrate that linearly polarized light, in contrast to conventional antiferromagnets, breaks the symmetry connecting spin sectors in altermagnets, allowing a series of spin-selective topological phase transitions from a quantum spin Hall state to a spin-polarized Chern insulator and finally to a trivial phase. The Nernst response shows substantial thermal activation and significant sensitivity to the gap size in the Chern domain, but both the electrical and thermal Hall responses become quantized and meet the anomalous Wiedemann Franz law. Every anomalous transport coefficient exhibits a distinctive d wave dependence on the polarization angle, reversing sign under orthogonal rotation and vanishing at symmetry-restoring directions. Our findings show a path to all-optical regulation of topological and caloritronic responses beyond traditional magnetic systems and establish thermal transport as a sensitive probe of altermagnetic order. △ Less

Submitted 25 June, 2026; v1 submitted 22 April, 2026; originally announced April 2026.

Topological magnetotransport in modified-Haldane systems

Authors: A. Uzair, Muzamil Shah, Imtiaz Khan, Kashif Sabeeh

Abstract: We present a theoretical study of quantum magneto-transport and magneto-optical (M-O) properties in modified-Haldane model; which is applicable to diverse classes of two-dimensional (2D) quantum materials such as buckled Xene monolayers and transition metal dichalcogenide (TMDC) monolayers. By varying the staggered sublattice potential and intrinsic spin-orbit coupling, we identify distinct topolo… ▽ More We present a theoretical study of quantum magneto-transport and magneto-optical (M-O) properties in modified-Haldane model; which is applicable to diverse classes of two-dimensional (2D) quantum materials such as buckled Xene monolayers and transition metal dichalcogenide (TMDC) monolayers. By varying the staggered sublattice potential and intrinsic spin-orbit coupling, we identify distinct topological regimes and analyze their manifestations in the emergence of Landau levels, the evolution of the density of states, and the characteristics of M-O absorption spectra. Using the Kubo formalism, we compute the longitudinal and Hall M-O conductivities and show that inter-Landau-level (inter-LL) transitions produce characteristic resonance features that provide optical signatures of the underlying topological phases. Within this framework, we demonstrate electrically tunable topological phase transitions in buckled silicene. Extending our study to monolayer TMDCs, we show that inspite of large band gap, the spin-valley coupling provides a powerful tool for tailoring M-O absorption features across wide range of 2D materials. Collectively, these results underscore modified-Haldane-model materials as an ideal testbed for engineering quantum transport, with promising applications in topological photonics, valleytronic devices, and next-generation optoelectronics. △ Less

Submitted 1 April, 2026; originally announced April 2026.

Floquet-driven thermal transport in topological Haldane lattice systems

Authors: Imtiaz Khan, Muzamil Shah, Ambreen Uzair, Reza Asgari, Gao Xianlong

Abstract: In this paper, we employ a modified Haldane lattice model to investigate the light-driven, spin- and valley-dependent anomalous Nernst effect in two-dimensional hexagonal topological systems. We demonstrate that two-dimensional buckled materials exhibit a hierarchy of electrically and optically tunable topological phases when subjected to off-resonant circularly polarized light in the presence of… ▽ More In this paper, we employ a modified Haldane lattice model to investigate the light-driven, spin- and valley-dependent anomalous Nernst effect in two-dimensional hexagonal topological systems. We demonstrate that two-dimensional buckled materials exhibit a hierarchy of electrically and optically tunable topological phases when subjected to off-resonant circularly polarized light in the presence of intrinsic spin-orbit coupling and a staggered sublattice potential. Within a Berry-curvature-driven transport framework, we systematically analyze charge-, spin-, and valley-resolved anomalous Nernst responses and identify their correspondence with distinct topological regimes. A finite charge Nernst conductivity arises under optical driving combined with spin-orbit coupling, whereas the generation of a pure valley Nernst current requires the simultaneous presence of sublattice asymmetry and off-resonant light. Substrate-induced inversion asymmetry further enables thermally driven valley currents with tunable magnitude and sign. We find that single-spin and single-valley Nernst responses occur in selected insulating and metallic phases, while the valley Nernst signal is suppressed in spin-polarized and anomalous quantum Hall phases. Extending our analysis to monolayer MoS$_2$, we show that strong spin-orbit coupling and broken inversion symmetry allow fully spin- and valley-polarized Nernst currents over a broad energy window. The temperature dependence of the Nernst response exhibits characteristic signatures of topological phase transitions, establishing the anomalous Nernst effect as a sensitive probe of field-engineered band topology in two-dimensional Dirac materials. △ Less

Submitted 26 March, 2026; originally announced March 2026.

Comments: 14 pages, 9 figures

Interlayer Coupling and Floquet-Driven Topological Phases in Bilayer Haldane Lattices

Authors: Imtiaz Khan, Muzamil Shah, Reza Asgari, Gao Xianlong

Abstract: We investigate Floquet-driven topological phase transitions in an AB-stacked bilayer Haldane lattice with tunable intralayer hopping anisotropy. By combining interlayer hybridization, Haldane flux, and off-resonant circularly polarized light, we obtain controlled transitions among Dirac, semi-Dirac, and higher-Chern insulating phases. As the hopping anisotropy increases, the two inequivalent Dirac… ▽ More We investigate Floquet-driven topological phase transitions in an AB-stacked bilayer Haldane lattice with tunable intralayer hopping anisotropy. By combining interlayer hybridization, Haldane flux, and off-resonant circularly polarized light, we obtain controlled transitions among Dirac, semi-Dirac, and higher-Chern insulating phases. As the hopping anisotropy increases, the two inequivalent Dirac points move toward each other and merge at the Brillouin-zone $\mathbf{M}$ point, where a semi-Dirac dispersion emerges with linear and quadratic momentum dependence along orthogonal directions. In this regime, competition between the intrinsic Haldane mass and the Floquet-induced mass drives a sequence of sharp topological transitions with Chern numbers $C=0,\pm1,\pm2$. We further show that interlayer coupling qualitatively reshapes the Floquet band topology by inducing helicity-dependent and valley-selective band inversions at the K and K$'$ points, thereby stabilizing higher-Chern phases in the valence bands. These changes are accompanied by redistribution of the Berry curvature, bulk gap closings, and the collapse or sign reversal of quantized anomalous Hall plateaus. As the system approaches the semi-Dirac limit, the topological phase space narrows and disappears at the critical merger point, beyond which the system becomes topologically trivial even when it remains gapped. Overall, the bilayer geometry broadens the scope of Floquet topological control by enabling dynamically tunable higher-Chern phases and valley-dependent Hall responses governed by interlayer coupling and light helicity. △ Less

Submitted 25 March, 2026; originally announced March 2026.

Single impurity-induced localization transitions in electronic systems

Authors: Niaz Ali Khan, Munsif Jan, Muzamil Shah, Muhammad Sajid, Muhammad Mateen, Mushtaq Ali

Abstract: Anderson localization is a fundamental phenomenon in disordered quantum systems, where transport is suppressed by wave interference from extensive randomness. Moving beyond traditional multi-impurity scenarios, we investigate impurity-induced localization phenomena in low-dimensional tight-binding systems by focusing on the properties of impurity-generated bound states. By introducing a single on-… ▽ More Anderson localization is a fundamental phenomenon in disordered quantum systems, where transport is suppressed by wave interference from extensive randomness. Moving beyond traditional multi-impurity scenarios, we investigate impurity-induced localization phenomena in low-dimensional tight-binding systems by focusing on the properties of impurity-generated bound states. By introducing a single on-site impurity into an otherwise extended lattice, we demonstrate that the impurity can host a bound state whose spatial character undergoes a transition from extended to localized as the impurity strength surpasses a critical value. This transition pertains solely to the impurity state, while the bulk states of the host system remain extended. We characterize the localization behavior by analyzing two distinct spatial profiles of the bound states: one with symmetric decay and another with exponential decay from the impurity site. Our results highlight how a local perturbation can induce nontrivial localization behavior at the level of individual eigenstates, without implying a global localization transition of the underlying electronic system. △ Less

Submitted 2 March, 2026; originally announced March 2026.

Journal ref: Journal of Low Temperature Physics 222, 51 (2026)

Solvation Restructuring Accelerates Early SEI Nucleation in Lithium Metal Batteries

Authors: Syed Mustafa Shah, Mohammed Lemaalem, Anh T. Ngo

Abstract: The development of high-energy-density lithium metal batteries is limited by electrolyte instability and the poorly understood onset of solid-electrolyte interphase (SEI) formation. Here, we use AIMD-trained Deep Potential molecular dynamics to link electrolyte solvation structure to early SEI nucleation in \ce{LiTFSI}/DMC electrolytes. Increasing \ce{LiTFSI} concentration drives the electrolyte f… ▽ More The development of high-energy-density lithium metal batteries is limited by electrolyte instability and the poorly understood onset of solid-electrolyte interphase (SEI) formation. Here, we use AIMD-trained Deep Potential molecular dynamics to link electrolyte solvation structure to early SEI nucleation in \ce{LiTFSI}/DMC electrolytes. Increasing \ce{LiTFSI} concentration drives the electrolyte from solvent-separated ion pairs toward contact ion pairs and aggregates, with \SI{3.5}{M} showing the strongest anion coordination. This anion-rich environment promotes earlier interfacial Li--F/Li--O bond formation, faster consumption of intact \ce{TFSI-} and solvent, and a denser, LiF/Li$_2$O-rich nascent interphase, in contrast to the more organic-laden, phosphorus/fluorine-based interphase formed by a \SI{1}{M} \ce{LiPF6} reference electrolyte. These results show that bulk solvation architecture biases both the timing and chemistry of early SEI formation and suggest solvation control as a design handle for Li-metal electrolytes. △ Less

Submitted 14 August, 2026; v1 submitted 4 February, 2026; originally announced February 2026.

Atomic-Scale Mechanisms of Li-Ion Transport Mediated by Li10GeP2S12 in Composite Solid Polyethylene Oxide Electrolytes

Authors: Syed Mustafa Shah, Musawenkosi K. Ncube, Mohammed Lemaalem, Selva Chandrasekaran Selvaraj, Naveen K. Dandu, Alireza Kondori, Gayoon Kim, Adel Azaribeni, Mohammad Asadi, Anh T. Ngo, Larry A. Curtiss

Abstract: Polymer electrolytes incorporating Li$_{10}$GeP$_{2}$S$_{12}$ (LGPS) nanoparticles show promise for solid-state lithium batteries owing to their enhanced ionic conductivity, though the governing mechanisms remain unclear. We combine molecular dynamics (MD) simulations, experimental ionic conductivity measurements, and density functional theory (DFT) calculations to elucidate the effect of LGPS loa… ▽ More Polymer electrolytes incorporating Li$_{10}$GeP$_{2}$S$_{12}$ (LGPS) nanoparticles show promise for solid-state lithium batteries owing to their enhanced ionic conductivity, though the governing mechanisms remain unclear. We combine molecular dynamics (MD) simulations, experimental ionic conductivity measurements, and density functional theory (DFT) calculations to elucidate the effect of LGPS loading on polyethylene oxide (PEO) structure and Li-ion transport. MD and experimental results agree up to 10\% LGPS, showing a volcano-shaped conductivity trend driven by polymer segmental dynamics and interfacial effects. Beyond 10\%, experiments reveal additional conductivity enhancement unexplained by MD, suggesting a distinct transport regime. DFT calculations indicate that Li-ion migration at the PEO|LGPS interface proceeds via vacancy-mediated hopping, with low barriers favored by S-rich interfacial sites and hindered by Ge. These findings link interfacial chemistry and microstructure to Li-ion dynamics, offering guidelines for designing high-performance composite polymer electrolytes. △ Less

Submitted 28 March, 2026; v1 submitted 31 December, 2025; originally announced January 2026.

Wafer-Scale Single-Crystalline Monolayer Graphene

Authors: Johanna Huhtasaari, Joyal Jain Palakulam, Awse Salha, Per Hyldgaard, Elsebeth Schröder, Magnus Hårdensson Berntsen, Oscar Tjernberg, Manasi Shah, Rodrigo Martinez-Duarte, Hans He, Johannes Hofmann, Thilo Bauch, Naveen Shetty, Samuel Lara-Avila

Abstract: Producing large-area single-crystalline graphene is key to realizing its full potential in advanced applications, including twistronics. Yet, controlling graphene growth kinetics to avoid grain boundaries or multilayer growth remains challenging. Here, we demonstrate single-crystalline graphene free from multilayer domains via one-step delamination of epitaxial graphene from silicon carbide (SiC).… ▽ More Producing large-area single-crystalline graphene is key to realizing its full potential in advanced applications, including twistronics. Yet, controlling graphene growth kinetics to avoid grain boundaries or multilayer growth remains challenging. Here, we demonstrate single-crystalline graphene free from multilayer domains via one-step delamination of epitaxial graphene from silicon carbide (SiC). This is enabled by a specific surface reconstruction of 4H-SiC(0001) achieved in our growth conditions. High crystalline quality is confirmed by the observation of the half-integer quantum Hall effect -- the hallmark of monolayer graphene -- in near cm-sized crystals. The scalability of our process, explored with 4''-wafers, represents an advance toward large-scale integration of high-performance graphene applications. △ Less

Submitted 29 November, 2025; originally announced December 2025.

Melting point depression of charge density wave in 1T-TiSe$_2$ due to size effects

Authors: Saif Siddique, Mehrdad T. Kiani, Omri Lesser, Stephen D. Funni, Nishkarsh Agarwal, Maya Gates, Miti Shah, William Millsaps, Suk Hyun Sung, Noah Schnitzer, Lopa Bhatt, David A. Muller, Robert Hovden, Ismail El Baggari, Eun-Ah Kim, Judy J. Cha

Abstract: Classical nucleation theory predicts size-dependent nucleation and melting due to surface and confinement effects at the nanoscale. In correlated electronic states, observation of size-dependent nucleation and melting is rarely reported, likely due to the extremely small length scales necessary to observe such effects for electronic states. Here, using 1T-TiSe$_2$ nanoflakes as a prototypical two-… ▽ More Classical nucleation theory predicts size-dependent nucleation and melting due to surface and confinement effects at the nanoscale. In correlated electronic states, observation of size-dependent nucleation and melting is rarely reported, likely due to the extremely small length scales necessary to observe such effects for electronic states. Here, using 1T-TiSe$_2$ nanoflakes as a prototypical two-dimensional (2D) charge density wave (CDW) system, we perform in-situ cryogenic electron microscopy with temperature down to 20 K and observe size-dependent nucleation and melting of CDWs. Specifically, we observe a melting point depression of CDW for 1T-TiSe$_2$ flakes with lateral sizes less than 100 nm. By fitting experimental data to a Ginzburg-Landau model, we estimate a zero-temperature correlation length of 10--50 nm, which matches the reported CDW domain size for 1T-TiSe$_2$. As the flake size approaches the correlation length, the divergence of the CDW correlation length near the transition is cut off by the finite flake size, limiting long-range order and thereby lowering the transition temperature. For very small flakes whose size is close to the correlation length, we also observe absence of CDWs, as predicted by the model. We thus show that an electronic phase transition follows classical nucleation theory. △ Less

Submitted 20 September, 2025; originally announced September 2025.

Journal ref: Phys. Rev. B 113, 224106 (2026)

Mapping Microstructure: Manifold Construction for Accelerated Materials Exploration

Authors: Simon A. Mason, Megna N. Shah, Jeffrey P. Simmons, Dennis M. Dimiduk, Stephen R. Niezgoda

Abstract: Accelerating materials development requires quantitative linkages between processing, microstructure, and properties. In this work, we introduce a framework for mapping microstructure onto a low-dimensional material manifold that is parametrized by processing conditions. A key innovation is treating microstructure as a stochastic process, defined as a distribution of microstructural instances rath… ▽ More Accelerating materials development requires quantitative linkages between processing, microstructure, and properties. In this work, we introduce a framework for mapping microstructure onto a low-dimensional material manifold that is parametrized by processing conditions. A key innovation is treating microstructure as a stochastic process, defined as a distribution of microstructural instances rather than a single image, enabling the extraction of material state descriptors that capture the essential process-dependent features. We leverage the manifold hypothesis to assert that microstructural outcomes lie on a low-dimensional latent space controlled by only a few parameters. Using phase-field simulations of spinodal decomposition as a model material system, we compare multiple microstructure descriptors (two-point statistics, chord-length distributions, and persistent homology) in terms of two criteria: (1) intrinsic dimensionality of the latent space, and (2) invertibility of the processing-to-structure mapping. The results demonstrate that distribution-based descriptors can recover a two-dimensional latent structure aligned with the true processing parameters, yielding an invertible and physically interpretable mapping between processing and microstructure. In contrast, descriptors that do not account for microstructure variability either overestimate dimensionality or lose predictive fidelity. The constructed material manifold is shown to be locally continuous, wherein small changes in process variables correspond to smooth changes in microstructure descriptors. This data-driven manifold mapping approach provides a quantitative foundation for microstructure-informed process design and paves the way toward closed-loop optimization of processing--structure--property relationships in an integrated materials engineering context. △ Less

Submitted 19 May, 2026; v1 submitted 18 September, 2025; originally announced September 2025.

Liquid Helium Cryogenic TEM below 1 Å

Authors: Suk Hyun Sung, Maya Gates, Nishkarsh Agarwal, Yang Zhang, William Millsaps, Miti Shah, Emily Rennich, Cong Li, Pu Yu, Miaofang Chi, Benjamin H. Savitzky, Ismail El Baggari, Robert Hovden

Abstract: Next-generation cryogenic transmission electron microscopes (TEM) aim to achieve high-resolution imaging at ultracold sample temperatures (< 90 K) and over extended hold times. Lower temperatures enable atomic-scale characterization with improved beam and dose resilience for organic specimens and access to emergent electronic phases in quantum materials. Side-entry liquid helium cooling stages pre… ▽ More Next-generation cryogenic transmission electron microscopes (TEM) aim to achieve high-resolution imaging at ultracold sample temperatures (< 90 K) and over extended hold times. Lower temperatures enable atomic-scale characterization with improved beam and dose resilience for organic specimens and access to emergent electronic phases in quantum materials. Side-entry liquid helium cooling stages presently lack the mechanical and thermal stability required to support sub-Angstrom information transfer in modern TEM. Here we demonstrate sub-Angstrom atomic imaging TEM with a side-entry stage at specimen temperatures down to ~20K and with low stage drift and stable hold times. △ Less

Submitted 15 September, 2025; originally announced September 2025.

Quantum magnetotransport in monolayer $\mathrm{Pt_{2}HgSe_{3}}$

Authors: Muzamil Shah, Imtiaz Khan, Kashif Sabeeh, Muhammad Sabieh Anwar, Reza Asgari

Abstract: We present a theoretical framework to investigate quantum magnetotransport in monolayer jacutingaite, focusing on its response to external electric fields and off-resonant circularly polarized laser irradiation. Our analysis reveals a sequence of topological phase transitions triggered by tuning these external parameters. We find that the zeroth LL exhibits spin- and valley-polarized splitting, le… ▽ More We present a theoretical framework to investigate quantum magnetotransport in monolayer jacutingaite, focusing on its response to external electric fields and off-resonant circularly polarized laser irradiation. Our analysis reveals a sequence of topological phase transitions triggered by tuning these external parameters. We find that the zeroth LL exhibits spin- and valley-polarized splitting, leading to four distinct peaks in the DOSs for the $K$ and $K'$ valleys. Using the Kubo formalism, we calculate both longitudinal and Hall magneto-optical conductivities based on the Kane-Mele model. Our results demonstrate that external electric, magnetic, and off-resonant optical fields can control these conductivities. These findings highlight monolayer jacutingaite as a highly tunable platform with strong potential for future applications in photonics, optoelectronics, and topological quantum devices. △ Less

Submitted 12 June, 2025; originally announced June 2025.

Topological transport in monolayer jacutingaite

Authors: Muzamil Shah, Muhammad Sabieh Anwar

Abstract: Monolayer-jacutingaite (Pt2HgSe3) has been predicted to be the first large-gap Kane-Mele quantum spin Hall insulator. Materials in the jacutingaite family undergo topological phase transitions (TPTs), i.e., from a topologically non-trivial to a semimetallic phase and further to the normal insulating phase when exposed to electric fields and off-resonance, high-frequency and high-intensity laser ir… ▽ More Monolayer-jacutingaite (Pt2HgSe3) has been predicted to be the first large-gap Kane-Mele quantum spin Hall insulator. Materials in the jacutingaite family undergo topological phase transitions (TPTs), i.e., from a topologically non-trivial to a semimetallic phase and further to the normal insulating phase when exposed to electric fields and off-resonance, high-frequency and high-intensity laser irradiation. In this article, we investigate the rich tapestry of topological phases in this unique material in the presence of an appropriate choice of off-resonance circularly polarized laser fields and staggered sublattice potentials. The interplay of these stimuli with large spin-orbit coupling, due to the buckled structure of jacutingaite materials, results in the emergence of quantum spin Hall insulator, valley-spin-polarized metal, spin-polarized metal, photo-induced quantum Hall insulator, anomalous quantum Hall insulator and band insulator phases. By analyzing the band structures, we compute Berry curvatures in different topological regimes for the $K$ and $K'$ valleys. Furthermore, by using the Kubo formula, we calculate the spin-valley resolved longitudinal and Hall conductivities as a function of photon energies showing that the conductivities exhibit a strong topological state dependence. The photon energy of the intraband and interband optical transitions can be tuned by varying the electric and optical fields. Finally, we demonstrate that by modulating the chemical potential, some of the allowed optical transitions become Pauli blocked due to the optical selection rules △ Less

Submitted 22 December, 2024; originally announced December 2024.

First-principles exploration of the pressure dependent physical properties of Sn4Au: a superconducting topological semimetal

Authors: M. Abdul Hadi Shah, M. I. Naher, S. H. Naqib

Abstract: First-principles investigation within the density functional theory is utilized to explore the physical properties of a superconducting topological semimetal Sn4Au under pressure within the range of 0-5 GPa. According to the computed elastic moduli, the compound under study is classified as ductile and applied pressure enhances the ductility. The compound has very high level of dry lubricity and m… ▽ More First-principles investigation within the density functional theory is utilized to explore the physical properties of a superconducting topological semimetal Sn4Au under pressure within the range of 0-5 GPa. According to the computed elastic moduli, the compound under study is classified as ductile and applied pressure enhances the ductility. The compound has very high level of dry lubricity and machinability index. All the anisotropy factors demonstrate an elastically anisotropic nature. The electronic properties are investigated in view of the electronic band structure and density of states. The band structure reveals the topological semimetallic feature of Sn4Au while the density of states at the Fermi level decreases gradually with increasing pressure. Both ionic and covalent bondings are observed in Sn4Au. Optical parameters of Sn4Au are investigated at different pressures. The characteristic peaks in reflectivity, refractive index and photoconductivity exhibit a shift towards higher energy with increasing pressure for all polarizations of the electric field vector. The absorption coefficient and reflectivity spectra designate Sn4Au as a suitable system for optoelectronic applications. Moreover, the pressure dependent shifts in the electronic density of states at the Fermi level, the changes in the Debye temperature, and pressure induced variations in the repulsive Coulomb pseudopotential have been used to explore the effect of pressure on the superconducting transition temperature in this study. △ Less

Submitted 14 August, 2024; originally announced August 2024.

Atomic short-range order control of GeSn as a new degree of freedom for band engineering

Authors: Shang Liu, Yunfan Liang, Nirosh M. Eldose, Shunda Chen, Xiaochen Jin, Haochen Zhao, Manoj Shah, Jin-Hee Bae, Omar Concepcion, Fernando M. de Oliveira, Ilias Bikmukhametov, Xiaoxin Wang, Yuping Zeng, Dan Buca, Mansour Mortazavi, Damien West, Shengbai Zhang, Tianshu Li, Gregory J. Salamo, Shui-Qing Yu, Jifeng Liu

Abstract: Chemical short-range order (SRO) refers to preference or avoidance between neighboring atomic species, which significantly impacts the properties of advanced alloys. However, quantifying and further controlling SRO remains a major challenge, especially for semiconductor alloys. Inspired by theoretically predicted impact of SRO on the band structure of direct-bandgap GeSn for infrared photonics, we… ▽ More Chemical short-range order (SRO) refers to preference or avoidance between neighboring atomic species, which significantly impacts the properties of advanced alloys. However, quantifying and further controlling SRO remains a major challenge, especially for semiconductor alloys. Inspired by theoretically predicted impact of SRO on the band structure of direct-bandgap GeSn for infrared photonics, we quantify and compare SRO in GeSn grown by molecular beam epitaxy (MBE) vs. chemical vapor deposition (CVD) using atom probe tomography. Remarkably, MBE-grown GeSn exhibits a stronger preference for Sn-Sn 1st nearest neighbors and an even smaller bandgap than CVD-grown samples with 2 at.% higher Sn composition. First-principles modeling confirms that the bandgap reduction originates from differences in SRO and further indicates that these SRO variations arise from different surface terminations and growth temperatures between MBE and CVD. These findings suggest that controlling SRO during GeSn growth offers a new degree of freedom for band engineering to achieve lattice-matched, high-quality Si-based electronic/photonic devices. △ Less

Submitted 28 March, 2026; v1 submitted 2 July, 2024; originally announced July 2024.

Lagrangian Neural Networks for Reversible Dissipative Evolution

Authors: Veera Sundararaghavan, Megna N. Shah, Jeff P. Simmons

Abstract: There is a growing attention given to utilizing Lagrangian and Hamiltonian mechanics with network training in order to incorporate physics into the network. Most commonly, conservative systems are modeled, in which there are no frictional losses, so the system may be run forward and backward in time without requiring regularization. This work addresses systems in which the reverse direction is ill… ▽ More There is a growing attention given to utilizing Lagrangian and Hamiltonian mechanics with network training in order to incorporate physics into the network. Most commonly, conservative systems are modeled, in which there are no frictional losses, so the system may be run forward and backward in time without requiring regularization. This work addresses systems in which the reverse direction is ill-posed because of the dissipation that occurs in forward evolution. The novelty is the use of Morse-Feshbach Lagrangian, which models dissipative dynamics by doubling the number of dimensions of the system in order to create a mirror latent representation that would counterbalance the dissipation of the observable system, making it a conservative system, albeit embedded in a larger space. We start with their formal approach by redefining a new Dissipative Lagrangian, such that the unknown matrices in the Euler-Lagrange's equations arise as partial derivatives of the Lagrangian with respect to only the observables. We then train a network from simulated training data for dissipative systems such as Fickian diffusion that arise in materials sciences. It is shown by experiments that the systems can be evolved in both forward and reverse directions without regularization beyond that provided by the Morse-Feshbach Lagrangian. Experiments of dissipative systems, such as Fickian diffusion, demonstrate the degree to which dynamics can be reversed. △ Less

Submitted 26 May, 2024; v1 submitted 23 May, 2024; originally announced May 2024.

Interferometric Single-Shot Parity Measurement in an InAs-Al Hybrid Device

Authors: Morteza Aghaee, Alejandro Alcaraz Ramirez, Zulfi Alam, Rizwan Ali, Mariusz Andrzejczuk, Andrey Antipov, Mikhail Astafev, Amin Barzegar, Bela Bauer, Jonathan Becker, Umesh Kumar Bhaskar, Alex Bocharov, Srini Boddapati, David Bohn, Jouri Bommer, Leo Bourdet, Arnaud Bousquet, Samuel Boutin, Lucas Casparis, Benjamin James Chapman, Sohail Chatoor, Anna Wulff Christensen, Cassandra Chua, Patrick Codd, William Cole , et al. (137 additional authors not shown)

Abstract: The fusion of non-Abelian anyons or topological defects is a fundamental operation in measurement-only topological quantum computation. In topological superconductors, this operation amounts to a determination of the shared fermion parity of Majorana zero modes. As a step towards this, we implement a single-shot interferometric measurement of fermion parity in indium arsenide-aluminum heterostruct… ▽ More The fusion of non-Abelian anyons or topological defects is a fundamental operation in measurement-only topological quantum computation. In topological superconductors, this operation amounts to a determination of the shared fermion parity of Majorana zero modes. As a step towards this, we implement a single-shot interferometric measurement of fermion parity in indium arsenide-aluminum heterostructures with a gate-defined nanowire. The interferometer is formed by tunnel-coupling the proximitized nanowire to quantum dots. The nanowire causes a state-dependent shift of these quantum dots' quantum capacitance of up to 1 fF. Our quantum capacitance measurements show flux h/2e-periodic bimodality with a signal-to-noise ratio of 1 in 3.7 $μ$s at optimal flux values. From the time traces of the quantum capacitance measurements, we extract a dwell time in the two associated states that is longer than 1 ms at in-plane magnetic fields of approximately 2 T. These results are consistent with a measurement of the fermion parity encoded in a pair of Majorana zero modes that are separated by approximately 3 $μ$m and subjected to a low rate of poisoning by non-equilibrium quasiparticles. The large capacitance shift and long poisoning time enable a parity measurement error probability of 1%. △ Less

Submitted 2 April, 2024; v1 submitted 17 January, 2024; originally announced January 2024.

Comments: Added data on a second measurement of device A and a measurement of device B, expanded discussion of a trivial scenario. Refs added, author list updated

Journal ref: Nature 638, 651 (2025)

Photonic spin Hall effect in Haldane model materials

Authors: Muzamil Shah, Muhammad Sabieh Anwar, Reza Asgari, Gao Xianlong

Abstract: The photonic spin Hall effect of light beams reflected from the surfaces of various two-dimensional hexagonal crystalline structures, considering their associated time-reversal $\mathcal{T}$ and inversion $\mathcal{I}$ symmetries, is investigated. Employing the Haldane model with tunable parameters as a generic model, we examine the longitudinal and transverse spin-separations of the reflected bea… ▽ More The photonic spin Hall effect of light beams reflected from the surfaces of various two-dimensional hexagonal crystalline structures, considering their associated time-reversal $\mathcal{T}$ and inversion $\mathcal{I}$ symmetries, is investigated. Employing the Haldane model with tunable parameters as a generic model, we examine the longitudinal and transverse spin-separations of the reflected beam in both topological non-trivial and trivial systems. The study reveals that the sign switching of the PSHE in these materials is attributed to the non-trivial and trivial topology. By manipulating the interplay between spin-orbit coupling and external electric fields, we demonstrate topological phase transitions in buckled Xene monolayer materials through the photonic spin Hall effect. Different behaviors of the photonic spin Hall effect are observed in various topological phases within these materials. Additionally, we explore the reflected spin and valley-polarized spatial shifts in monolayer transition metal dichalcogenides. The photonic spin Hall effect in buckled Xene monolayer materials and transition metal dichalcogenides is highly influenced by the spin and valley degrees of freedom of charge carriers, offering a promising avenue to explore spintronics and valleytronics in these hexagonal materials. We propose that the photonic spin Hall effect in Haldane materials can serve as a metrological tool for optical parameter characterization and as a promising method for determining Chern numbers and topological phase transitions through direct optical weak measurement techniques. △ Less

Submitted 4 September, 2024; v1 submitted 12 December, 2023; originally announced December 2023.

Impact of the Fizeau drag effect on Goos-Hänchen shifts in graphene

Authors: Rafi Ud Din, Muzamil Shah, Reza Asgari, Gao Xianlong

Abstract: We investigate the Goos-Hänchen shifts in reflection for a light beam within a graphene structure, utilizing the Fizeau drag effect induced by its massless Dirac electrons in incident light. The magnitudes of spatial and angular shifts for a light beam propagating against the direction of drifting electrons are significantly enhanced, while shifts for a beam co-propagating with the drifting electr… ▽ More We investigate the Goos-Hänchen shifts in reflection for a light beam within a graphene structure, utilizing the Fizeau drag effect induced by its massless Dirac electrons in incident light. The magnitudes of spatial and angular shifts for a light beam propagating against the direction of drifting electrons are significantly enhanced, while shifts for a beam co-propagating with the drifting electrons are suppressed. The Goos-Hänchen shifts exhibit augmentation with increasing drift velocities of electrons in graphene. The impact of incident wavelength on the angular and spatial shifts in reflection is discussed. Furthermore, the study highlights the crucial roles of the density of charged particles in graphene, the particle relaxation time, and the thickness of the graphene in manipulating the drag-affected Goos-Hänchen shifts. This investigation offers valuable insights for efficiently guiding light in graphene structures under the influence of the Fizeau drag effect. △ Less

Submitted 6 March, 2024; v1 submitted 8 December, 2023; originally announced December 2023.

Comments: 11 pages, 7 figures

Towards Microstructural State Variables in Materials Systems

Authors: Veera Sundararaghavan, Megna N. Shah, Jeff P. Simmons

Abstract: The vast combination of material properties seen in nature are achieved by the complexity of the material microstructure. Advanced characterization and physics based simulation techniques have led to generation of extremely large microstructural datasets. There is a need for machine learning techniques that can manage data complexity by capturing the maximal amount of information about the microst… ▽ More The vast combination of material properties seen in nature are achieved by the complexity of the material microstructure. Advanced characterization and physics based simulation techniques have led to generation of extremely large microstructural datasets. There is a need for machine learning techniques that can manage data complexity by capturing the maximal amount of information about the microstructure using the least number of variables. This paper aims to formulate dimensionality and state variable estimation techniques focused on reducing microstructural image data. It is shown that local dimensionality estimation based on nearest neighbors tend to give consistent dimension estimates for natural images for all p-Minkowski distances. However, it is found that dimensionality estimates have a systematic error for low-bit depth microstructural images. The use of Manhattan distance to alleviate this issue is demonstrated. It is also shown that stacked autoencoders can reconstruct the generator space of high dimensional microstructural data and provide a sparse set of state variables to fully describe the variability in material microstructures. △ Less

Submitted 10 January, 2023; originally announced January 2023.

Financial Risk Management on a Neutral Atom Quantum Processor

Authors: Lucas Leclerc, Luis Ortiz-Guitierrez, Sebastian Grijalva, Boris Albrecht, Julia R. K. Cline, Vincent E. Elfving, Adrien Signoles, Loïc Henriet, Gianni Del Bimbo, Usman Ayub Sheikh, Maitree Shah, Luc Andrea, Faysal Ishtiaq, Andoni Duarte, Samuel Mugel, Irene Caceres, Michel Kurek, Roman Orus, Achraf Seddik, Oumaima Hammammi, Hacene Isselnane, Didier M'tamon

Abstract: Machine Learning models capable of handling the large datasets collected in the financial world can often become black boxes expensive to run. The quantum computing paradigm suggests new optimization techniques, that combined with classical algorithms, may deliver competitive, faster and more interpretable models. In this work we propose a quantum-enhanced machine learning solution for the predict… ▽ More Machine Learning models capable of handling the large datasets collected in the financial world can often become black boxes expensive to run. The quantum computing paradigm suggests new optimization techniques, that combined with classical algorithms, may deliver competitive, faster and more interpretable models. In this work we propose a quantum-enhanced machine learning solution for the prediction of credit rating downgrades, also known as fallen-angels forecasting in the financial risk management field. We implement this solution on a neutral atom Quantum Processing Unit with up to 60 qubits on a real-life dataset. We report competitive performances against the state-of-the-art Random Forest benchmark whilst our model achieves better interpretability and comparable training times. We examine how to improve performance in the near-term validating our ideas with Tensor Networks-based numerical simulations. △ Less

Submitted 3 April, 2024; v1 submitted 6 December, 2022; originally announced December 2022.

Comments: 17 pages, 11 figures, 2 tables, revised version

Journal ref: Phys. Rev. Research 5, 043117 (2023)

Zero-energy states in graphene quantum dot with wedge disclination

Authors: Ahmed Bouhlal, Ahmed Jellal, Nurisya Mohd Shah

Abstract: We investigate the effects of wedge disclination on charge carriers in circular graphene quantum dots subjected to a magnetic flux. Using the asymptotic solutions of the energy spectrum for large arguments, we approximate the scattering matrix elements, and then study the density of states. It is found that the density of states shows several resonance peaks under various conditions. In particular… ▽ More We investigate the effects of wedge disclination on charge carriers in circular graphene quantum dots subjected to a magnetic flux. Using the asymptotic solutions of the energy spectrum for large arguments, we approximate the scattering matrix elements, and then study the density of states. It is found that the density of states shows several resonance peaks under various conditions. In particular, it is shown that the wedge disclination is able to change the amplitude, width, and positions of resonance peaks. △ Less

Submitted 9 August, 2022; originally announced August 2022.

Comments: 10 pages, 10 figures

Radiative Pattern of Intralayer and Interlayer Excitons in Two-Dimensional WS2/WSe2 Heterostructure

Authors: Mohammed Adel Aly, Manan Shah, Lorenz Maximilian Schneider, Kyungnam Kang, Martin Koch, Eui-Hyeok Yang, Arash Rahimi-Iman

Abstract: Two-dimensional (2D) heterostructures (HS) formed by transition-metal dichalcogenide (TMDC) monolayers offer a unique platform for the study of intralayer and interlayer excitons as well as moiré-pattern-induced features. Particularly, the dipolar charge-transfer exciton comprising an electron and a hole, which are confined to separate layers of 2D semiconductors and Coulomb-bound across the heter… ▽ More Two-dimensional (2D) heterostructures (HS) formed by transition-metal dichalcogenide (TMDC) monolayers offer a unique platform for the study of intralayer and interlayer excitons as well as moiré-pattern-induced features. Particularly, the dipolar charge-transfer exciton comprising an electron and a hole, which are confined to separate layers of 2D semiconductors and Coulomb-bound across the heterojunction interface, has drawn considerable attention in the research community. On the one hand, it bears significance for optoelectronic devices, e.g. in terms of charge carrier extraction from photovoltaic devices. On the other hand, its spatially indirect nature and correspondingly high longevity among excitons as well as its out-of-plane dipole orientation render it attractive for excitonic Bose-Einstein condensation studies, which address collective coherence effects, and for photonic integration schemes with TMDCs. Here, we demonstrate the interlayer excitons' out-of-plane dipole orientation through angle-resolved spectroscopy of the HS photoluminescence at cryogenic temperatures, employing a tungsten-based TMDC HS. Within the measurable light cone, the directly-obtained radiation profile of this species clearly resembles that of an in-plane emitter which deviates from that of the intralayer bright excitons as well as the other excitonic HS features recently attributed to artificial superlattices formed by moiré patterns. △ Less

Submitted 12 November, 2021; originally announced November 2021.

Complete Magneto-Optic Modulation of Lateral and Angular Shifts in Spin-Orbit Coupled Members of the Graphene Family

Authors: Muzamil Shah, Muahmmad Sabieh Anwar

Abstract: The intrinsic spin-orbit coupling in the 2D staggered monolayer semiconductors is very large as compared to graphene. The large spin orbit interaction in these materials leads to the opening of a gap in the energy spectrum and spin-splitting of the bands in each valley. In this paper, we theoretically investigate the mechanical steering of beams from these spin-orbit rich, staggered 2D materials.… ▽ More The intrinsic spin-orbit coupling in the 2D staggered monolayer semiconductors is very large as compared to graphene. The large spin orbit interaction in these materials leads to the opening of a gap in the energy spectrum and spin-splitting of the bands in each valley. In this paper, we theoretically investigate the mechanical steering of beams from these spin-orbit rich, staggered 2D materials. Mechanical steering results in noticeable deviations of the reflected and transmitted ray profiles as predicted from classical laws of optics. These effects are generally called the Goos-Hanchen (GH) and Imbert-Fedorov shifts. We find that electric and magnetic field modulated giant spatial and angular GH shifts can be achieved in these materials for incident angles in the vicinity of Brewster angle in terahertz regime. We also determine the dependence of beam shifts on the chemical potential and find that the Brewster angle and the sign of GH shift can be controlled by varying the chemical potential. This allows the possibility of realizing spin and valley dependent optical effects that can be useful readout markers for experiments in quantum information processing, biosensing and valleytronics, employed in the terahertz regime. △ Less

Submitted 23 December, 2019; originally announced December 2019.

Comments: 12 pages, 6 figures

Magneto-optical effects in the Landau level manifold of 2D lattices with spin-orbit interaction

Authors: Muzamil Shah, Muhammad Sabieh Anwar

Abstract: Silicene is a competitive and promising 2D material, possessing interesting topological, electronic and optical properties. The presence of strong spin orbit interaction in silicene and its analogues, germanene and tinene, leads to the opening of a gap in the energy spectrum and spin-splitting of the bands in each valley. We develop a general method to determine the magneto-optic response of silic… ▽ More Silicene is a competitive and promising 2D material, possessing interesting topological, electronic and optical properties. The presence of strong spin orbit interaction in silicene and its analogues, germanene and tinene, leads to the opening of a gap in the energy spectrum and spin-splitting of the bands in each valley. We develop a general method to determine the magneto-optic response of silicene, when a Gaussian beam is incident on silicene grown on a dielectric substrate in the presence of a static magnetic field. We use a semiclassical treatment of silicene monolayer to describe the Faraday rotation (FR) and Magneto-optical Kerr effect (MOKE) using a general model for beam propagation. The response can be modulated both electrically and magnetically. We derive analytic expressions for valley and spin polarized FR and MOKE for arbitrary polarization of incident light in the terahertz regime. We demonstrate that large FR and MOKE can be achieved by tuning the electric field, magnetic fields and chemical potential in these fascinating 2D materials. Implications for novel valleytronic experiments are also discussed. △ Less

Submitted 2 May, 2019; v1 submitted 14 February, 2019; originally announced February 2019.

Comments: 10 pages; 3 figures

A Broadband Superabsorber at Optical Frequencies: Design and Demonstration

Authors: Arvind Nagarajan, Kumar Vivek, Manav Shah, Venu Gopal Achanta, Giampiero Gerini

Abstract: Metasurface based super absorbers exhibit near unity absorbance. While the absorption peak can be tuned by the geometry/size of the sub-wavelength resonator, broadband absorption can be obtained by placing multiple resonators of various size or shapes in a unit cell. Metal dispersion hinders high performance broadband absorption at optical frequencies and careful designing is essential to achieve… ▽ More Metasurface based super absorbers exhibit near unity absorbance. While the absorption peak can be tuned by the geometry/size of the sub-wavelength resonator, broadband absorption can be obtained by placing multiple resonators of various size or shapes in a unit cell. Metal dispersion hinders high performance broadband absorption at optical frequencies and careful designing is essential to achieve good structures. We propose a novel analytical framework for designing a broadband super absorber which is much faster than the time consuming full wave simulations that are employed so far. Analytical expressions are derived for the wavelength dependency of the design parameters, which are then used in the optimization of broadband absorption. Numerical simulations report an average polarization-independent absorption of ~97 in the 450 to 950 nm spectral region with a near unity absorption (99.36) in the 500 to 850 nm region. Experimentally, we demonstrate an average absorption over 98 in the 450 to 950 nm spectral region at 20 degree incident angle The designed super absorber is polarization insensitive and has a weak launch angle dependency. The proposed framework simplifies the design process and provides a quicker optimal solution for high performance broadband super absorbers. △ Less

Submitted 23 April, 2018; originally announced April 2018.

Journal ref: Advanced Optical Materials 6 (16), 1800253, 2018