Showing 1–50 of 176 results for author: Chen, A

A CMOS-compatible, scalable and compact magnetoelectric spin-torque microwave detector

Authors: Shuhui Liu, Riccardo Tomasello, Bin Fang, Aitian Chen, Like Zhang, Zhenhao Liu, Rui Hu, Wenkui Lin, Mario Carpentieri, Baoshun Zhang, Xixiang Zhang, Giovanni Finocchio, Zhongming Zeng

Abstract: The development of compact and highly sensitive microwave detectors compatible with complementary-metal-oxide-semiconductor (CMOS) processes is an active research area but remains a major challenge in microwave technology. Spin-torque diodes (STDs) are emerging nanoscale spintronic devices capable of surpassing the theoretical thermodynamic sensitivity limits of Schottky diodes. However, their pra… ▽ More The development of compact and highly sensitive microwave detectors compatible with complementary-metal-oxide-semiconductor (CMOS) processes is an active research area but remains a major challenge in microwave technology. Spin-torque diodes (STDs) are emerging nanoscale spintronic devices capable of surpassing the theoretical thermodynamic sensitivity limits of Schottky diodes. However, their practical use in compact systems is limited by the need of external antennas or probes. Here, we demonstrate a magnetoelectric (ME) spin-torque microwave detector that monolithically integrates an ME antenna with a magnetic tunnel junction (MTJ). The device directly converts wireless electromagnetic signals into a DC output at sub-microwatt power levels, achieving a sensitivity greater than 90 kV/W, a noise equivalent power of 3 pW*Hz^-0.5, and a compact footprint of 0.4 mm^2. This performance is due to the nonlinear coupling between incoherent magnetization dynamics, driven by a DC current in the MTJ, and the combined effects of the microwave voltage and strain generated by the ME antenna under incident electromagnetic waves. We further show that this design is scalable, enabling the co-integration of an ME antenna with an array of MTJs. A detector incorporating four MTJs, for example, exhibits a sensitivity exceeding 400 kV/W. This work paves the way for a new generation of highly sensitive, compact and scalable microwave detectors that combine ME antennas and spintronic diodes. △ Less

Submitted 14 April, 2026; originally announced April 2026.

Thermodynamic fluctuations in freely jointed chains under force

Authors: Michael R. Buche, Alvin Chen

Abstract: It is common to study polymer physics through the use of idealized single-chain models, and the most popular of these is the freely jointed chain model. In certain thermodynamic ensembles, statistical mechanical treatment of this model is analytically tractable or sometimes exactly solvable. This enables useful relations to be ascertained, like the expected chain end-to-end length as a function of… ▽ More It is common to study polymer physics through the use of idealized single-chain models, and the most popular of these is the freely jointed chain model. In certain thermodynamic ensembles, statistical mechanical treatment of this model is analytically tractable or sometimes exactly solvable. This enables useful relations to be ascertained, like the expected chain end-to-end length as a function of an applied force. However, most of these relations return ensemble averages, which are values with inherent uncertainty, as opposed to deterministic values with no variance. This is an important distinction to understand and quantify, because the majority of studies to date involving single-chain models effectively treat these values as deterministic rather than fluctuating. To address this issue, thermodynamic fluctuations are examined in the freely jointed chain model. Specifically, the probability densities and standard deviations of the longitudinal, lateral, transverse, and radial portions of the chain extension, as well as the extension and link angles, are examined for different numbers of links and applied forces. Fluctuations in these quantities are shown to be considerable until the applied force becomes large. Increasing the number of links in the chain gradually reduces fluctuations in all quantities except for the link angles, since they are independent for freely jointed chains in the isotensional ensemble. Quantities are obtained analytically whenever possible and numerically otherwise. Overall, these results provide intuitive admonitions to consider when modeling the stretching of single polymer chains or the deformation of entire polymer networks. △ Less

Submitted 13 April, 2026; originally announced April 2026.

Tunable anharmonicity in Sn-InAs nanowire transmons beyond the short junction limit

Authors: Amrita Purkayastha, Amritesh Sharma, Param J. Patel, An-Hsi Chen, Connor P. Dempsey, Shreyas Asodekar, Subhayan Sinha, Maxime Tomasian, Mihir Pendharkar, Christopher J. Palmstrøm, Moïra Hocevar, Kun Zuo, Michael Hatridge, Sergey M. Frolov

Abstract: The anharmonicity of a transmon qubit, defined as the difference in energy level spacing, is a key design parameter. In transmons built from hybrid superconductor-semiconductor Josephson elements, the anharmonicity is tunable with gate voltages that control both the Josephson energy and the weak link transparency. In Sn-InAs nanowire transmons, we use two-tone microwave spectroscopy to extract anh… ▽ More The anharmonicity of a transmon qubit, defined as the difference in energy level spacing, is a key design parameter. In transmons built from hybrid superconductor-semiconductor Josephson elements, the anharmonicity is tunable with gate voltages that control both the Josephson energy and the weak link transparency. In Sn-InAs nanowire transmons, we use two-tone microwave spectroscopy to extract anharmonicity ranging in absolute value from the transmon charging energy $E_c$ to values smaller than $E_c/10$. This behavior contrasts with the predictions of the multi-channel short-junction model, which sets a lower limit on anharmonicity at $E_c/4$. Coherent operation of the qubit is still possible at the point of the lowest anharmonicity. These findings demonstrate the potential of quantum circuits that benefit from widely electrically tunable anharmonicity. △ Less

Submitted 27 March, 2026; originally announced March 2026.

Spin crossover in FeO under shock compression

Authors: Lélia Libon, Alessandra Ravasio, Silvia Pandolfi, Yanyao Zhang, Xuehui Wei, Jean-Alexis Hernandez, Hong Yang, Amanda J. Chen, Tommaso Vinci, Alessandra Benuzzi-Mounaix, Clemens Prescher, François Soubiran, Hae Ja Lee, Eric Galtier, Nick Czapla, Wendy L. Mao, Arianna E. Gleason, Sang Heon Shim, Roberto Alonso-Mori, Guillaume Morard

Abstract: FeO (wüstite), which exhibits complex electronic and structural properties with increasing pressure and temperature, is a key mineralogical phase for understanding deep planetary interiors. However, direct measurements of its spin state at high-pressure and temperature remain challenging in static compression experiments. Here, we employ laser-driven shock compression to extend the FeO principal H… ▽ More FeO (wüstite), which exhibits complex electronic and structural properties with increasing pressure and temperature, is a key mineralogical phase for understanding deep planetary interiors. However, direct measurements of its spin state at high-pressure and temperature remain challenging in static compression experiments. Here, we employ laser-driven shock compression to extend the FeO principal Hugoniot up to $\sim$900 GPa and perform in situ X-ray diffraction and X-ray emission spectroscopy up to 250 GPa, probing FeO's crystal structure and spin state. We demonstrate a continuous spin crossover of iron in FeO over a broad pressure range, with the high-spin state persisting beyond Earth's core-mantle boundary (CMB) conditions. These observations provide new experimental constraints on iron spin state at extreme conditions essential for geophysical models of (exo)planetary interiors. △ Less

Submitted 17 March, 2026; originally announced March 2026.

Comments: 35 pages, 6 figures, under review

Intrinsic Even-Odd Thickness-Driven Anomalous Hall in Epitaxial MnBi2Te4 Thin Films

Authors: Debarghya Mallick, Simon Kim, An-Hsi Chen, Gabriel A. Vázquez-Lizardi, Alessandro R. Mazza, T. Zac Ward, Gyula Eres, Yue Cao, Debangshu Mukherjee, Hu Miao, Liang Wu, Christopher Nelson, Danielle Reifsnyder Hickey, Robert G. Moore, Matthew Brahlek

Abstract: We demonstrate precise control of magnetism in MnBi2Te4 thin films through careful synthesis by molecular beam epitaxy, achieving minimal defects and accurate layer thickness control. By optimizing Mn-Bi-Te ratios and growth temperatures, we minimize detrimental self-doping effects and accurately target integer-layer films. X-ray diffraction and reflectivity provide quantitative measures of film q… ▽ More We demonstrate precise control of magnetism in MnBi2Te4 thin films through careful synthesis by molecular beam epitaxy, achieving minimal defects and accurate layer thickness control. By optimizing Mn-Bi-Te ratios and growth temperatures, we minimize detrimental self-doping effects and accurately target integer-layer films. X-ray diffraction and reflectivity provide quantitative measures of film quality and thickness. When these macroscale probes of structure and thickness are integrated with magnetotransport measurements, a striking even-odd layer dependence of the anomalous Hall effect is revealed. Odd-layer films exhibit a large hysteresis up to the Néel temperature (~25K), consistent with non-compensated antiferromagnetism, while even-layer films show minimal response, as expected for an antiferromagnet. The sign of the anomalous Hall effect exhibits a sign reversal for intrinsic magnetism versus magnetism associated with defects. This work identifies critical factors for inducing pure, non-compensated ferromagnetism and reveals the character of the intrinsic anomalous Hall effect in MnBi2Te4, which together is a step towards realizing the zero-field quantum anomalous Hall effect in topological materials. △ Less

Submitted 11 March, 2026; originally announced March 2026.

Comments: Accepted in Physical Review Materials

Physics-informed neural operator for predictive parametric phase-field modelling

Authors: Nanxi Chen, Airong Chen, Rujin Ma

Abstract: Predicting the microstructural and morphological evolution of materials through phase-field modelling is computationally intensive, particularly for high-throughput parametric studies. While neural operators such as the Fourier neural operator (FNO) show promise in accelerating the solution of parametric partial differential equations (PDEs), the lack of explicit physical constraints, may limit ge… ▽ More Predicting the microstructural and morphological evolution of materials through phase-field modelling is computationally intensive, particularly for high-throughput parametric studies. While neural operators such as the Fourier neural operator (FNO) show promise in accelerating the solution of parametric partial differential equations (PDEs), the lack of explicit physical constraints, may limit generalisation and long-term accuracy for complex phase-field dynamics. Here, we develop a physics-informed neural operator framework to learn parametric phase-field PDEs, namely PF-PINO. By embedding the residuals of phase-field governing equations into the data-fidelity loss function, our framework effectively enforces physical constraints during training. We validate PF-PINO against benchmark phase-field problems, including electrochemical corrosion, dendritic crystal solidification, and spinodal decomposition. Our results demonstrate that PF-PINO significantly outperforms conventional FNO in accuracy, generalisation capability, and long-term stability. This work provides a robust and efficient computational tool for phase-field modelling and highlights the potential of physics-informed neural operators to advance scientific machine learning for complex interfacial evolution problems. △ Less

Submitted 10 March, 2026; originally announced March 2026.

Doping evolution of spin excitations in La$_{3-x}$Sr$_{x}$Ni$_2$O$_7$/SrLaAlO$_4$ superconducting thin films

Authors: Hengyang Zhong, Bo Hao, Anni Chen, Xinru Huang, Chunyi Li, Wenting Zhang, Chang Liu, Kurt Kummer, Nicholas Brookes, Yuefeng Nie, Thorsten Schmitt, Xingye Lu

Abstract: Ambient-pressure superconductivity in compressively strained bilayer nickelate films enables direct spectroscopic tests of pairing scenarios, yet how magnetism evolves with carrier doping remains largely unexplored. Here we use Ni $L_3$-edge resonant inelastic x-ray scattering (RIXS) to track electronic and spin excitations in coherently strained La$_{3-x}$Sr$_x$Ni$_2$O$_7$/SrLaAlO$_4$ thin films… ▽ More Ambient-pressure superconductivity in compressively strained bilayer nickelate films enables direct spectroscopic tests of pairing scenarios, yet how magnetism evolves with carrier doping remains largely unexplored. Here we use Ni $L_3$-edge resonant inelastic x-ray scattering (RIXS) to track electronic and spin excitations in coherently strained La$_{3-x}$Sr$_x$Ni$_2$O$_7$/SrLaAlO$_4$ thin films ($x=0$, $0.09$, $0.21$ and $0.38$), spanning superconducting and overdoped non-superconducting regimes at essentially fixed epitaxial strain. Transport confirms superconductivity for $x\le0.21$ and a weakly insulating normal state at $x=0.38$. The $dd$-excitation manifold evolves weakly up to $x=0.21$, whereas the $\sim0.4$ eV and $\sim1.6$ eV features broaden and lose intensity at $x=0.38$. In the superconducting films, dispersive spin excitations persist along both $[H, H]$ and $[H, 0]$ with nearly doping-independent undamped dispersions and only a modest reduction of spectral weight, consistent with robust double-stripe correlations. By contrast, at $x=0.38$ the magnetic response becomes strongly broadened and weakened, with enhanced damping and $\sim50\%$ lower spectral weight, indicating a collapse of coherent double-stripe spin excitations. The concomitant suppression of magnetic coherence and superconductivity establishes a direct doping-controlled link between magnetism and superconductivity in bilayer nickelate films. △ Less

Submitted 1 March, 2026; originally announced March 2026.

Comments: 8 pages, 4 figures

Strain patterning of flexomagnetism

Authors: Tamalika Samanta, Zachary T. LaDuca, An-Hsi Chen, Sangsoo Kim, Ying-Ting Chan, Jiaxuan Wu, Yujia Teng, Debarghya Mallick, Matthew Brahlek, T. Zac Ward, Katherine Su, Jia-Mian Hu, Weida Wu, Turan Birol, Hanfei Yan, Michael S. Arnold, Karin M. Rabe, Jason K. Kawasaki

Abstract: Flexomagnetism, the coupling of magnetic ordering to strain gradients, provides access to novel symmetry-broken magnetic phases that cannot be accessed via uniform strain. However, flexomagnetism is hard to understand because it is extremely difficult to control a spatially varying strain. Here, we develop a top-down strategy to pattern transverse strain gradients using helium ion implantation thr… ▽ More Flexomagnetism, the coupling of magnetic ordering to strain gradients, provides access to novel symmetry-broken magnetic phases that cannot be accessed via uniform strain. However, flexomagnetism is hard to understand because it is extremely difficult to control a spatially varying strain. Here, we develop a top-down strategy to pattern transverse strain gradients using helium ion implantation through a lithographically defined mask. Using epitaxial films of the antiferromagnetic nodal line semimetal GdAuGe, we demonstrate that transverse strain gradients $\partial \varepsilon_{zz}/\partial x$ induce near-room-temperature ferromagnetic response, compared to the retained para or antiferromagnetism for homogeneously strained GdAuGe. We spatially correlate the magnetic response with the regions of largest strain gradient, via magnetic force microscopy and nanobeam x-ray diffraction, respectively, to confirm the flexomagnetic response. Our approach opens new avenues for the precise control of magnetic phases in thin films of quantum materials via a patterned strain gradient. △ Less

Submitted 26 February, 2026; originally announced February 2026.

Self-avoiding tethered surfaces are always flat

Authors: A. D. Chen, M. C. Gandikota, M. J. Kim, A. Cacciuto

Abstract: The scaling behavior of fully flexible elastic tethered surfaces has been debated for decades. Some theories predict that self-avoiding surfaces would crumple in the absence of bending rigidity, while most simulations suggested that they would remain flat. Recent simulations on ideal membranes with lattice perforations suggest that systematically removing surface area from a membrane may provide a… ▽ More The scaling behavior of fully flexible elastic tethered surfaces has been debated for decades. Some theories predict that self-avoiding surfaces would crumple in the absence of bending rigidity, while most simulations suggested that they would remain flat. Recent simulations on ideal membranes with lattice perforations suggest that systematically removing surface area from a membrane may provide an alternative way to crumpling self-avoiding surfaces. We perform extensive numerical simulations of two models of fully flexible elastic tethered surfaces in which self-avoidance can be systematically and continuously tuned to the ideal limit. We show that in the thermodynamic limit, these surfaces remain flat with a size exponent $ν=1$ for any finite degree of self-avoidance, with or without membrane perforations. △ Less

Submitted 25 February, 2026; originally announced February 2026.

Comments: 8 pages, 9 figures

Simulating superconductivity in mixed-dimensional $t_\parallel$-${J}_\parallel$-${J}_\perp$ bilayers with neural quantum states

Authors: Hannah Lange, Ao Chen, Antoine Georges, Fabian Grusdt, Annabelle Bohrdt, Christopher Roth

Abstract: Motivated by the recent discovery of superconductivity in the bilayer nickelate La$_3$Ni$_2$O$_7$ (LNO) under pressure, we study a mixed-dimensional (mixD) bilayer $t_\parallel$-$J_\parallel$-$J_\perp$ model, which has been proposed as an effective low-energy description of LNO. Using neural quantum states (NQS), and in particular Gutzwiller-projected Hidden Fermion Pfaffian State, we access the g… ▽ More Motivated by the recent discovery of superconductivity in the bilayer nickelate La$_3$Ni$_2$O$_7$ (LNO) under pressure, we study a mixed-dimensional (mixD) bilayer $t_\parallel$-$J_\parallel$-$J_\perp$ model, which has been proposed as an effective low-energy description of LNO. Using neural quantum states (NQS), and in particular Gutzwiller-projected Hidden Fermion Pfaffian State, we access the ground-state properties on large lattices up to $8\times 8\times 2$ sites. We show that this model exhibits superconductivity across a wide range of dopings and couplings, and analyze the pairing behavior in detail. We identify a crossover from tightly bound, Bose-Einstein-condensed interlayer pairs at strong interlayer exchange to more spatially extended Bardeen-Cooper-Schrieffer-like pairs as the interlayer exchange is decreased. Furthermore, upon tuning the intralayer exchange, we observe a sharp transition from interlayer $s$-wave pairing to intralayer $d$-wave pairing, consistent with a first-order change in the pairing symmetry. We verify that our simulations are accurate by comparing with matrix product state simulations on coupled ladders. Our results represent the first simulation of a fermionic multi-orbital system with NQS, and provide the first evidence for superconductivity in two-dimensonal bilayers using high-precision numerics. These findings provide insight into superconductivity in bilayer nickelates and cold atom quantum simulation platforms. △ Less

Submitted 10 February, 2026; originally announced February 2026.

Comments: 7 pages + Supplementary Materials

lrux: Fast low-rank updates of determinants and Pfaffians in JAX

Authors: Ao Chen, Christopher Roth

Abstract: We present lrux, a JAX-based software package for fast low-rank updates of determinants and Pfaffians, targeting the dominant computational bottleneck in various quantum Monte Carlo (QMC) algorithms. The package implements efficient low-rank updates that reduce the cost of successive wavefunction evaluations from $\mathcal{O}(n^3)$ to $\mathcal{O}(n^2k)$ when the update rank $k$ is smaller than th… ▽ More We present lrux, a JAX-based software package for fast low-rank updates of determinants and Pfaffians, targeting the dominant computational bottleneck in various quantum Monte Carlo (QMC) algorithms. The package implements efficient low-rank updates that reduce the cost of successive wavefunction evaluations from $\mathcal{O}(n^3)$ to $\mathcal{O}(n^2k)$ when the update rank $k$ is smaller than the dimension $n$ of matrices. Both determinant and Pfaffian updates are supported, together with delayed-update strategies that trade floating-point operations for reduced memory traffic on modern accelerators. lrux natively integrates with JAX transformations such as JIT compilation, vectorization, and automatic differentiation, and supports both real and complex data types. Benchmarks on GPUs demonstrate up to $1000\times$ speedup at large matrix sizes. lrux enables scalable, high-performance evaluation of antisymmetric wavefunctions and is designed as a drop-in component for a wide range of QMC workflows. lrux is available at https://github.com/ChenAo-Phys/lrux. △ Less

Submitted 4 February, 2026; originally announced February 2026.

Quantum Metric Length as a Fundamental Length Scale in Disordered Flat Band Materials

Authors: Chun Wang Chau, Tian Xiang, Shuai A. Chen, K. T. Law

Abstract: Our previous understanding of electronic transport in disordered systems was based on the assumption that there is a finite Fermi velocity for the relevant electrons. The Fermi velocity determines important length scales in disordered systems such as the diffusion length and the localization length. However, in disordered systems with vanishing or nearly vanishing Fermi velocity, it is uncertain w… ▽ More Our previous understanding of electronic transport in disordered systems was based on the assumption that there is a finite Fermi velocity for the relevant electrons. The Fermi velocity determines important length scales in disordered systems such as the diffusion length and the localization length. However, in disordered systems with vanishing or nearly vanishing Fermi velocity, it is uncertain what determines the important length scales in such systems. In this work, we use the 1D Lieb lattice with isolated flat bands as an example to show that the quantum metric length (QML) is a fundamental length scale in the ballistic, diffusive and localization regimes. The QML is defined through the Bloch state wave functions of the flat bands. In the ballistic regime with short junctions, the QML controls the finite energy transport properties. In the localization regime with long junctions, the localization length is determined by the QML and remarkably, independent of disorder strength over a wide range of disorder strength. We call this unconventional localization regime, the quantum metric localization regime. In the diffusive regime, we demonstrate that the diffusion coefficient is linearly proportional to the QML via the wave-packet dynamics numerically. Importantly, the numerical results are consistent with the analytical results obtained through the Bethe-Salpeter equation. We conclude that the QML is a fundamentally important length scale governing the properties of disordered flat band materials. △ Less

Submitted 1 February, 2026; originally announced February 2026.

Comments: This manuscript supersedes arXiv:2412.19056

Quasiparticle to local moment crossover in bad metals

Authors: A. Chen, F. B. Kugler, P. Doležal, Y. Saito, A. Kawamoto, A. Georges, A. Pustogow

Abstract: Non-Fermi-liquid charge transport in the vicinity of electronic instabilities has been intensely studied for decades. Deviations from $ρ_{\rm FL}=ρ_0+AT^2$ in bad and strange metals are commonly ascribed to a breakdown of Landau's quasiparticle (QP) concept. Yet, it remains unclear what mechanism drives the temperature dependence of $ρ(T)$ beyond $ρ_{\rm FL}$. Here, we examine the bad metal upon a… ▽ More Non-Fermi-liquid charge transport in the vicinity of electronic instabilities has been intensely studied for decades. Deviations from $ρ_{\rm FL}=ρ_0+AT^2$ in bad and strange metals are commonly ascribed to a breakdown of Landau's quasiparticle (QP) concept. Yet, it remains unclear what mechanism drives the temperature dependence of $ρ(T)$ beyond $ρ_{\rm FL}$. Here, we examine the bad metal upon approaching the Mott metal-insulator transition via chemical pressure in $κ$-[(BEDT-STF)$_x$(BEDT-TTF)$_{1-x}$]$\rm _2 Cu_2 (CN)_3$. Through nuclear magnetic resonance (NMR) and transport experiments on the same single crystals, we directly link the onset of deviations from Korringa law $(T_1T)^{-1} = \mathrm{const.}$ with the rise of $ρ(T)$ beyond $ρ_{\rm FL}$. From the NMR relaxation rate, we can identify the gradual crossover between the QP-dominated regime at low $T$ to predominant local moments at higher $T$. By comparing our experimental findings with dynamical mean-field theory calculations, which accurately reproduce the transport data, we reveal how this crossover is reflected in $T$-dependent changes of the QP spectrum. Near the Mott insulator, where $dρ/dT<0$ at high $T$, an Einstein-relation analysis shows that bad-metal behavior with $dρ/dT>0$ is driven by the temperature dependence of the electronic compressibility rather than the diffusion constant. △ Less

Submitted 14 January, 2026; originally announced January 2026.

Scale-Rich Network-Based Metamaterials

Authors: Csaba Both, Andrew Yen-Jong Chen, Ting-Ting Gao, Niek Mooij, Mohammad Charara, Carlos M. Portela, Albert-László Barabási

Abstract: Materials, at their essence, are networks defined by homogeneity: uniform bonds, fixed thicknesses, and discrete length scales. Mechanical metamaterials, while representing structurally more diverse microstructures, remain defined by the homogeneity of their unit cells, pore sizes, or repeating features. In contrast, as network science has revealed, real-world and biological systems -- from the In… ▽ More Materials, at their essence, are networks defined by homogeneity: uniform bonds, fixed thicknesses, and discrete length scales. Mechanical metamaterials, while representing structurally more diverse microstructures, remain defined by the homogeneity of their unit cells, pore sizes, or repeating features. In contrast, as network science has revealed, real-world and biological systems -- from the Internet to the brain -- derive their function from broad, multiscale variability in connectivity and link length. Here, we introduce Scale-Rich (SR) metamaterials, a design framework that embeds network heterogeneity into mechanical metamaterials, achieving order-of-magnitude heterogeneity in ligament lengths, thicknesses, and connectivity. Governed by only two parameters, SR networks span orders of magnitude in structural features, overcoming prior constraints in metamaterial design. Translating these network models into physically realizable materials, we use simulations and experiments to show that SR metamaterials exhibit properties inaccessible to traditional single-scale systems, including highly tunable elastic anisotropy, delocalized nonlinear deformation with high energy absorption, and programmable acoustic wave control. This network-science-based paradigm establishes a minimal yet universal framework for engineering multifunctional materials whose mechanical and acoustic behavior emerge directly from scale diversity itself. △ Less

Submitted 22 November, 2025; originally announced November 2025.

Superconductivity in the two-dimensional Hubbard model revealed by neural quantum states

Authors: Christopher Roth, Ao Chen, Anirvan Sengupta, Antoine Georges

Abstract: Whether the ground state of the square lattice Hubbard model exhibits superconductivity remains a major open question, central to understanding high temperature cuprate superconductors and ultra-cold fermions in optical lattices. Numerical studies have found evidence for stripe-ordered states and superconductivity at strong coupling but the phase diagram remains controversial. Here, we show that o… ▽ More Whether the ground state of the square lattice Hubbard model exhibits superconductivity remains a major open question, central to understanding high temperature cuprate superconductors and ultra-cold fermions in optical lattices. Numerical studies have found evidence for stripe-ordered states and superconductivity at strong coupling but the phase diagram remains controversial. Here, we show that one can resolve the subtle energetics of metallic, superconducting, and stripe phases using a new class of neural quantum state (NQS) wavefunctions that extend hidden fermion determinant states to Pfaffians. We simulate several hundred electrons using fast Pfaffian algorithms allowing us to measure off-diagonal long range order. At strong coupling and low hole-doping, we find that a non-superconducting filled stripe phase prevails, while superconductivity coexisting with partially-filled stripes is stabilized by a negative next neighbor hopping t-prime, with |t-prime| > 0.1. At larger doping levels, we introduce momentum-space correlation functions to mitigate finite size effects that arise from weakly-bound pairs. These provide evidence for uniform d-wave superconductivity at U = 4, even when t-prime = 0. Our results highlight the potential of NQS approaches, and provide a fresh perspective on superconductivity in the square lattice Hubbard model. △ Less

Submitted 10 November, 2025; originally announced November 2025.

Weak localization and universal conductance fluctuations in large area twisted bilayer graphene

Authors: Spenser Talkington, Debarghya Mallick, An-Hsi Chen, Benjamin F. Mead, Seong-Jun Yang, Cheol-Joo Kim, Shaffique Adam, Liang Wu, Matthew Brahlek, Eugene J. Mele

Abstract: We study diffusive magnetotransport in highly p-doped large area twisted bilayer graphene samples as a function of twist angle, crossing from 1° (below), to 20° (above) the van Hove singularity with 7° and 9° samples near the van Hove singularity. We report weak localization in twisted bilayer graphene for the first time. All samples exhibit weak localization, from which we extract the phase coher… ▽ More We study diffusive magnetotransport in highly p-doped large area twisted bilayer graphene samples as a function of twist angle, crossing from 1° (below), to 20° (above) the van Hove singularity with 7° and 9° samples near the van Hove singularity. We report weak localization in twisted bilayer graphene for the first time. All samples exhibit weak localization, from which we extract the phase coherence length and intervalley scattering lengths, and from that determine that dephasing is caused by electron-electron scattering and intervalley scattering is caused by point defects. We observe signatures of universal conductance fluctuations in the 9° sample, which has high mobility and is near the van Hove singularity. Further improvements in sample quality and applications to large area moire materials will open new avenues to observe quantum interference effects. △ Less

Submitted 2 December, 2025; v1 submitted 10 November, 2025; originally announced November 2025.

Comments: 5+1 pages, 3+1 figures; v2 updated references

Higher-dimensional Fermiology in bulk moiré metals

Authors: Kevin P. Nuckolls, Nisarga Paul, Alan Chen, Filippo Gaggioli, Joshua P. Wakefield, Avi Auslender, Jules Gardener, Austin J. Akey, David Graf, Takehito Suzuki, David C. Bell, Liang Fu, Joseph G. Checkelsky

Abstract: In the past decade, moiré materials have revolutionized how we engineer and control quantum phases of matter. Among incommensurate materials, moiré materials are aperiodic composite crystals whose long-wavelength moiré superlattices enable tunable properties without chemically modifying their layers. To date, nearly all reports of moiré materials have investigated van der Waals heterostructures as… ▽ More In the past decade, moiré materials have revolutionized how we engineer and control quantum phases of matter. Among incommensurate materials, moiré materials are aperiodic composite crystals whose long-wavelength moiré superlattices enable tunable properties without chemically modifying their layers. To date, nearly all reports of moiré materials have investigated van der Waals heterostructures assembled far from thermodynamic equilibrium. Here we introduce a conceptually new approach to synthesizing high-mobility moiré materials in thermodynamic equilibrium. We report a new family of foliated superlattice materials (Sr$_6$TaS$_8$)$_{1+δ}$(TaS$_2$)$_8$ that are exfoliatable van der Waals crystals with atomically incommensurate lattices. Lattice mismatches between alternating layers generate moiré superlattices, analogous to those of 2D moiré heterobilayers, that are coherent throughout these crystals and are tunable through their synthesis conditions without altering their chemical composition. High-field quantum oscillation measurements map the complex Fermiology of these moiré metals, which can be tuned via the moiré superlattice structure. We find that the Fermi surface of the structurally simplest moiré metal is comprised of over 40 distinct cross-sectional areas, the most observed in any material to our knowledge. This can be naturally understood by postulating that bulk moiré materials can encode electronic properties of higher-dimensional superspace crystals in ways that parallel well-established crystallographic methods used for incommensurate lattices. More broadly, our work demonstrates a scalable synthesis approach potentially capable of producing moiré materials for electronics applications and evidences a novel material design concept for accessing a broad range of physical phenomena proposed in higher dimensions. △ Less

Submitted 30 October, 2025; originally announced October 2025.

Comments: 26 pages, 5 figures

Journal ref: Nature 651, 333-340 (2026)

Magnetically Responsive Microprintable Soft Nanocomposites with Tunable Nanoparticle Loading

Authors: Rachel M. Sun, Andrew Y. Chen, Yiming Ji, Daryl W. Yee, Carlos M. Portela

Abstract: Magnetic remote actuation of soft materials has been demonstrated at the macroscale using hard-magnetic particles for applications such as transforming materials and medical robots. However, due to manufacturing limitations, few microscale magnetically responsive devices exist -- light-based additive manufacturing methods, which are ideal for realizing microscale features, struggle with light scat… ▽ More Magnetic remote actuation of soft materials has been demonstrated at the macroscale using hard-magnetic particles for applications such as transforming materials and medical robots. However, due to manufacturing limitations, few microscale magnetically responsive devices exist -- light-based additive manufacturing methods, which are ideal for realizing microscale features, struggle with light scattering induced by the magnetic particles. Moreover, large hard-magnetic microparticles prevent high-resolution features from being manufactured altogether, and soft-magnetic nanoparticles require impractically high loading and high magnetic gradients, incompatible with existing printing techniques. Among successfully fabricated microscale soft-magnetic composites, limited control over magnetic-particle loading, distribution, and matrix-phase stiffness has hindered their functionality. Here, we combine two-photon lithography with iron-oxide nanoparticle co-precipitation to fabricate 3D-printed microscale nanocomposites having features down to 8 um with spatially tunable nanoparticle distribution. Using uniaxial compression experiments and vibrating sample magnetometry, we characterize the mechanical and magnetic properties of the composite, achieving millimeter-scale elastic deformations. We control nanoparticle content by modulating laser power of the print to imbue complex parts with magnetic functionality, demonstrated by a soft robotic gripper and a bistable bit register and sensor. This approach enables precise control of structure and functionality, advancing the development of microscale metamaterials and robots with tunable mechanical and magnetic properties. △ Less

Submitted 8 October, 2025; originally announced October 2025.

Comments: 28 pages, 6 figures, 6 supplementary figures

AtomWorld: A Benchmark for Evaluating Spatial Reasoning in Large Language Models on Crystalline Materials

Authors: Taoyuze Lv, Alexander Chen, Fengyu Xie, Chu Wu, Jeffrey Meng, Dongzhan Zhou, Yingheng Wang, Bram Hoex, Zhicheng Zhong, Tong Xie

Abstract: Large Language Models (LLMs) excel at textual reasoning and are beginning to develop spatial understanding, prompting the question of whether these abilities can be combined for complex, domain-specific tasks. This question is essential in fields like materials science, where deep understanding of 3D atomic structures is fundamental. While initial studies have successfully applied LLMs to tasks in… ▽ More Large Language Models (LLMs) excel at textual reasoning and are beginning to develop spatial understanding, prompting the question of whether these abilities can be combined for complex, domain-specific tasks. This question is essential in fields like materials science, where deep understanding of 3D atomic structures is fundamental. While initial studies have successfully applied LLMs to tasks involving pure crystal generation or coordinate understandings, a standardized benchmark to systematically evaluate their core reasoning abilities across diverse atomic structures has been notably absent. To address this gap, we introduce the AtomWorld benchmark to evaluate LLMs on tasks based in Crystallographic Information Files (CIFs), a standard structure representation format. These tasks, including structural editing, CIF perception, and property-guided modeling, reveal a critical limitation: current models, despite establishing promising baselines, consistently fail in structural understanding and spatial reasoning. Our experiments show that these models make frequent errors on structure modification tasks, and even in the basic CIF format understandings, potentially leading to cumulative errors in subsequent analysis and materials insights. By defining these standardized tasks, AtomWorld lays the ground for advancing LLMs toward robust atomic-scale modeling, crucial for accelerating materials research and automating scientific workflows. △ Less

Submitted 22 January, 2026; v1 submitted 6 October, 2025; originally announced October 2025.

Long-lived dynamics of the charge density wave in TiSe$_2$ observed by neutron scattering

Authors: K. Dharmasiri, S. S. Philip, D. Louca, S. A. Chen, M. D. Frontzek, Z. J. Morgan, C. Hua

Abstract: Time-resolved elastic neutron scattering combined with rapid laser heating was used to probe the charge density wave (CDW) state in 1T-TiSe$_2$, capturing both the melting and reformation of the CDW on long timescales and providing clues on the roles of phonons and excitons. With the laser source on, superlattice Bragg peaks such as (-1.5, -1.5, 1.5) observed below the CDW transition due to the ne… ▽ More Time-resolved elastic neutron scattering combined with rapid laser heating was used to probe the charge density wave (CDW) state in 1T-TiSe$_2$, capturing both the melting and reformation of the CDW on long timescales and providing clues on the roles of phonons and excitons. With the laser source on, superlattice Bragg peaks such as (-1.5, -1.5, 1.5) observed below the CDW transition due to the new lattice periodicity, dissipate within 5 seconds, at a rate that is much slower than the sample's thermal response to the heat wave propagation. Whereas the electronic ordering associated with the CDW phase is disrupted rapidly by the laser-induced heating, the periodic lattice distortion (PLD) exhibits a markedly slower evolution during the melting process. This delayed suppression of the PLD relative to the thermal response indicates that CDW melting proceeds through a nonthermal pathway, likely linked to the loss of superlattice phonons such as the soft mode at q = (0.5 ,0, 0.5 ). △ Less

Submitted 18 September, 2025; originally announced September 2025.

Comments: 12 pages, 12 figures

Persistent Fluctuating Superconductivity and Planckian Dissipation in Fe(Te,Se)

Authors: Jonathan Stensberg, Pok Man Tam, Xiaoyu Yuan, Xiong Yao, Heshan Yu, Chih-Yu Lee, An-Hsi Chen, Philip J. D. Crowley, Matthew Brahlek, Ichiro Takeuchi, Seongshik Oh, Joseph Orenstein, Charles Kane, Liang Wu

Abstract: Increasingly intricate phase diagrams in new classes of superconductors host fascinating interactions between superconductivity, diverse quantum phases, and quantum critical dynamics. The native superfluids, however, often exhibit much lower density and much greater inhomogeneity than conventional superfluids. This may render the superconductivity susceptible to fluctuations that are ordinarily as… ▽ More Increasingly intricate phase diagrams in new classes of superconductors host fascinating interactions between superconductivity, diverse quantum phases, and quantum critical dynamics. The native superfluids, however, often exhibit much lower density and much greater inhomogeneity than conventional superfluids. This may render the superconductivity susceptible to fluctuations that are ordinarily assumed to be frozen out far below the superconducting transition temperature $T_c$, calling into question the degree to which the superconducting state is fully coherent. In this work, we leverage terahertz spectroscopy to demonstrate strongly fluctuating superconductivity in topological compositions of the multiband iron-based superconductor Fe(Te,Se). These fluctuations are found to persist undiminished far below $T_c$ and converge upon the limit of Planckian dissipation above $T_c$. These results indicate that extended quantum fluctuations dominate the electrodynamics of both the superconducting and Planckian-dissipative precursor states of Fe(Te,Se), and demonstrate that the assumption of phase coherence must be rigorously validated in emerging classes of unconventional superconductors. △ Less

Submitted 17 September, 2025; originally announced September 2025.

Comments: 6 pages, 8 figures

Neural-Quantum-States Impurity Solver for Quantum Embedding Problems

Authors: Yinzhanghao Zhou, Tsung-Han Lee, Ao Chen, Nicola Lanatà, Hong Guo

Abstract: Neural quantum states (NQS) have emerged as a promising approach to solve second-quantized Hamiltonians, because of their scalability and flexibility. In this work, we design and benchmark an NQS impurity solver for the quantum embedding (QE) methods, focusing on the ghost Gutzwiller Approximation (gGA) framework. We introduce a graph transformer-based NQS framework able to represent arbitrarily c… ▽ More Neural quantum states (NQS) have emerged as a promising approach to solve second-quantized Hamiltonians, because of their scalability and flexibility. In this work, we design and benchmark an NQS impurity solver for the quantum embedding (QE) methods, focusing on the ghost Gutzwiller Approximation (gGA) framework. We introduce a graph transformer-based NQS framework able to represent arbitrarily connected impurity orbitals of the embedding Hamiltonian (EH) and develop an error control mechanism to stabilize iterative updates throughout the QE loops. We validate the accuracy of our approach with benchmark gGA calculations of the Anderson Lattice Model, yielding results in excellent agreement with the exact diagonalisation impurity solver. Finally, our analysis of the computational budget reveals the method's principal bottleneck to be the high-accuracy sampling of physical observables required by the embedding loop, rather than the NQS variational optimization, directly highlighting the critical need for more efficient inference techniques. △ Less

Submitted 13 March, 2026; v1 submitted 15 September, 2025; originally announced September 2025.

Comments: 10 pages main text, and 4 figures. Note that YinZhangHao Zhou and Zhanghao Zhouyin are the same person, I use them both

Nanosculpting lateral weak link junctions in superconducting Fe(Te,Se)/Bi2Te3 with focused Si++ ions and implications on vortex pinning

Authors: Debarghya Mallick, Sujoy Ghosh, An Hsi Chen, Qiangsheng Lu, Liam Collins, Sangsoo Kim, Gyula Eres, Ivan Kravchenko, Stephen Jesse, Steven J. Randolph, Scott T. Retterer, Matthew Brahlek, Robert G. Moore

Abstract: Superconductor-normal-superconductor (SC-N-SC) weak links enable Cooper-pair tunneling and serve as Josephson junctions (JJs) used in modern superconducting qubits. Conventional JJs rely on vertically stacked Al-AlOx-Al trilayers that are difficult to fabricate and are sensitive to ambient exposure. Here, we demonstrate an all-in-plane alternative by "nanosculpting" ~100 nm-wide channels into thin… ▽ More Superconductor-normal-superconductor (SC-N-SC) weak links enable Cooper-pair tunneling and serve as Josephson junctions (JJs) used in modern superconducting qubits. Conventional JJs rely on vertically stacked Al-AlOx-Al trilayers that are difficult to fabricate and are sensitive to ambient exposure. Here, we demonstrate an all-in-plane alternative by "nanosculpting" ~100 nm-wide channels into thin films of FeTe0.75Se0.25/Bi2Te3 (FTS/BT), a candidate topological superconductor, with a Si++ focusses ion beam (FIB). Systematic irradiation shows that increasing the ion dose, while keeping the beam energy constant, progressively suppresses both the critical temperature (Tc) and critical current (Ic), confirming the creation of a controllable weak link even though a Fraunhofer interference pattern is not observed. Kelvin prove force microscopy , atomic force microscopy and scanning electron microscopy corroborate the structural and electronic modification of the irradiated region. Ic (B) measurements reveal a slower field-induced decay of Ic at higher doses, indicating that irradiation-induced defects act as vortex-pinning centers that mitigate vortex motion and associated dissipation, By tuning beam energy and dose, the process shifts from SC-N-SC regime toward a superconductor-insulator-superconductor (SC-I-SC) geometry, offering a simple scalable pathway to JJ fabrication. These results established FIB pattering as a versatile platform for engineering robust, scalable fault-tolerant qubits. △ Less

Submitted 12 September, 2025; originally announced September 2025.

Mechanical performance of hybrid polymer-lipid vesicles with leaflet asymmetry engineered using microfluidics

Authors: Yuting Huang, Arash Manafirad, Simon Matoori, Laura R. Arriaga, Sijie Sun, Anqi Chen, Anthony D. Dinsmore, David J. Mooney, David A. Weitz

Abstract: Lipid vesicles consist of aqueous cores surrounded by a bilayer of phospholipids. Hybrid polymer-lipid vesicles incorporate both polymers and lipids, offering promising properties for developing pharmaceuticals, biosensors, and artificial cells. The hybrid vesicles can be symmetric, in which their two leaflets contain identical compositions, or asymmetric, in which the leaflets possess dissimilar… ▽ More Lipid vesicles consist of aqueous cores surrounded by a bilayer of phospholipids. Hybrid polymer-lipid vesicles incorporate both polymers and lipids, offering promising properties for developing pharmaceuticals, biosensors, and artificial cells. The hybrid vesicles can be symmetric, in which their two leaflets contain identical compositions, or asymmetric, in which the leaflets possess dissimilar compositions and can lead to dramatically modified properties. However, methods to produce both symmetric and asymmetric hybrid vesicles result in heterogenous compositions and sizes, making it challenging to quantify the effect of asymmetry and limiting applications. Here, we use a microfluidic approach to produce hybrid vesicles containing symmetric or asymmetric leaflets with precisely engineered compositions. We find the vesicles with asymmetric leaflets are significantly stiffer and tougher than those with symmetric leaflets; moreover, the lateral diffusivity of lipids is greatly decreased. The structure for improved toughness consists of an inner leaflet that is a stretchable lipid leaflet and an outer leaflet that is a fully continuous polymer leaflet. This technique of precisely engineering asymmetric structures may be applied to hybrid vesicles composed of block copolymers and phospholipids dissolvable in chloroform and hexane, further expanding their applications. △ Less

Submitted 2 September, 2025; originally announced September 2025.

Disorder-induced proximate quantum spin ice phase in Pr$_2$Sn$_2$O$_7$

Authors: Yi Luo, Joseph A. M. Paddison, Brenden R. Ortiz, Miles Knudtson, Stephen D. Wilson, Jue Liu, Benjamin A. Frandsen, Si Athena Chen, Matthias Frontzek, Andrey Podlesnyak, Adam A. Aczel

Abstract: We report a comprehensive bulk characterization and neutron scattering investigation of single-crystalline Pr$_2$Sn$_2$O$_7$, a magnetic pyrochlore synthesized via a flux-growth method. Unpolarized neutron diffuse scattering reveals the emergence of spin-ice correlations below $T \sim 1$ K, evidenced by the development of anisotropic pinch-point features that are consistent with quantum-spin-ice (… ▽ More We report a comprehensive bulk characterization and neutron scattering investigation of single-crystalline Pr$_2$Sn$_2$O$_7$, a magnetic pyrochlore synthesized via a flux-growth method. Unpolarized neutron diffuse scattering reveals the emergence of spin-ice correlations below $T \sim 1$ K, evidenced by the development of anisotropic pinch-point features that are consistent with quantum-spin-ice (QSI) behavior. A.C. susceptibility measurements indicate a progressive slowing of spin dynamics in this regime, culminating in complete spin freezing below $T_f \approx 0.15$ K. Inelastic neutron scattering at $T = 0.5$ K reveals a broad spectrum of quasi-elastic magnetic excitations, with intensity in the low-energy range $[0, 0.2]$ meV significantly suppressed below $T_f$. Meanwhile, an incipient (100)-type magnetic order begins to nucleate, and a gapped excitation centered at $\hbarω= 0.23$ meV persists. We further identify two distinct dynamical timescales above $T_f$, a slow component $τ_{\mathrm{slow}} \sim 10^{-5}$ s and a fast component $τ_{\mathrm{fast}} \sim 10^{-10}$ s, in quantitative agreement with theoretical predictions for QSI systems. Taken together, these results indicate that Pr$_2$Sn$_2$O$_7$ enters a disorder-induced spin-frozen phase below $T_f$, lying in close proximity to a $U(1)$ quantum spin liquid. △ Less

Submitted 16 September, 2025; v1 submitted 26 August, 2025; originally announced August 2025.

Comments: 21 pages, 17 figures, 2 tables. v2 (09/16/2025): Fixed typos and DOIs in references; added neutron data reduction software citation in Methods; included additional references in Introduction

Transmon qubit using Sn as a junction superconductor

Authors: Amrita Purkayastha, Amritesh Sharma, Param J. Patel, An-Hsi Chen, Connor P. Dempsey, Shreyas Asodekar, Subhayan Sinha, Maxime Tomasian, Mihir Pendharkar, Christopher J. Palmstrøm, Moïra Hocevar, Kun Zuo, Michael Hatridge, Sergey M. Frolov

Abstract: Superconductor qubits typically use aluminum-aluminum oxide tunnel junctions to provide the non-linear inductance. Junctions with semiconductor barriers make it possible to vary the superconductor material and explore beyond aluminum. We use InAs semiconductor nanowires coated with thin superconducting shells of beta-Sn to realize transmon qubits. By tuning the Josephson energy with a gate voltage… ▽ More Superconductor qubits typically use aluminum-aluminum oxide tunnel junctions to provide the non-linear inductance. Junctions with semiconductor barriers make it possible to vary the superconductor material and explore beyond aluminum. We use InAs semiconductor nanowires coated with thin superconducting shells of beta-Sn to realize transmon qubits. By tuning the Josephson energy with a gate voltage, we adjust the qubit frequency over a range of 3 GHz. The longest energy relaxation time, T1 = 27 microseconds, is obtained at the lowest qubit frequencies, while the longest echo dephasing time, T2 = 1.8 microseconds, is achieved at higher frequencies. We assess the possible factors limiting coherence times in these devices and discuss steps to enhance performance through improvements in materials fabrication and circuit design. △ Less

Submitted 5 August, 2025; originally announced August 2025.

Comments: Data and code available at https://zenodo.org/records/16732149

Quantum confinement effect in Sb thin films

Authors: Anuradha Wijesinghe, Yongxi Ou, Anjali Rathore, Chandima Edirisinghe, Pradip Adhikari, An-Hsi Chen, Dustin Gilbert, Anthony Richardella, Nitin Samarth, Joon Sue Lee

Abstract: Antimony (Sb), an element with strong spin-orbit coupling, is predicted to undergo a topological phase transition from a topological semimetal to a topological insulator as its dimensionality approaches the two-dimensional limit, driven by the quantum confinement effect. In this study, we investigate this transition in Sb thin films grown by molecular beam epitaxy, employing electrical transport m… ▽ More Antimony (Sb), an element with strong spin-orbit coupling, is predicted to undergo a topological phase transition from a topological semimetal to a topological insulator as its dimensionality approaches the two-dimensional limit, driven by the quantum confinement effect. In this study, we investigate this transition in Sb thin films grown by molecular beam epitaxy, employing electrical transport measurements and angle-resolved photoemission spectroscopy (ARPES). Electrical transport measurements revealed signatures of a modified electronic band structure, including a Hall response with multiple carrier types, a decreasing carrier concentration, and a transition in the curvature of the longitudinal resistance from quadratic to linear with decreasing film thickness. Temperature-dependent magnetoresistance further showed weak antilocalization below 16 K, indicating strong spin-orbit coupling and suggesting the presence of non-trivial topological states. Analysis of the WAL characteristics revealed a single coherent conducting channel and a thickness-dependent change in the phase decoherence mechanism. Complementary ARPES measurements confirmed that reducing the film thickness lifts the conduction band at the M-point, consistent with the emergence of a band gap. These findings support theoretical predictions of a thickness-dependent band structure evolution driven by the quantum confinement effect, providing a foundation for further exploration of topological phase transitions in Sb as well as Bi1-xSbx. The realization of an elemental topological material with simplified stoichiometry and semiconductor compatibility presents a promising avenue for next-generation hybrid systems and applications in spintronics and quantum technologies. △ Less

Submitted 30 July, 2025; originally announced July 2025.

Comments: 19 pages, 10 figures

Programmable phase selection between altermagnetic and non-centrosymmetric polymorphs of MnTe on InP via molecular beam epitaxy

Authors: An-Hsi Chen, Parul R. Raghuvanshi, Jacob Cook, Michael Chilcote, Jason Lapano, Alessandro R. Mazza, Qiangsheng Lu, Sangsoo Kim, Yueh-Chun Wu, T. Zac Ward, Benjamin Lawrie, Guang Bian, James Burns, Jonathan D. Poplawsky, Myung-Geun Han, Yimei Zhu, Lucas Lindsay, Hu Miao, Robert G. Moore, Gyula Eres, Valentino R. Cooper, Matthew Brahlek

Abstract: Phase selecting nearly degenerate crystalline polymorphs during epitaxial growth can be challenging yet is critical to targeting physical properties for specific applications. Here, we establish how phase selectivity of altermagnetic and non-centrosymmetric polymorphs of MnTe with high structural quality and phase purity can be programmed by subtle changes to the surface of lattice-matched InP sub… ▽ More Phase selecting nearly degenerate crystalline polymorphs during epitaxial growth can be challenging yet is critical to targeting physical properties for specific applications. Here, we establish how phase selectivity of altermagnetic and non-centrosymmetric polymorphs of MnTe with high structural quality and phase purity can be programmed by subtle changes to the surface of lattice-matched InP substrates in molecular beam epitaxial (MBE) growth. Bulk altermagnetic MnTe is thermodynamically stable in the hexagonal NiAs-structure and is synthesized here on the (111)A surface (In-terminated) of InP, while the non-centrosymmetric, cubic ZnS-structure with wide band gap (> 3eV) is stabilized on the (111)B surface (P-terminated). Here we use electron microscopy, photoemission spectroscopy, and reflection high-energy electron diffraction, which together indicate that the phase selection is triggered at the interface and proceeds along the growing surface. First principles calculations suggest that interfacial termination and strain have a significant effect on the interfacial energy; stabilizing the NiAs polymorph on the In-terminated surface and the ZnS structure on the P-terminated surface. Selectively grown, high-quality films of MnTe polymorphs are key platforms that will enable our understanding of the novel properties of these materials, thereby facilitating their use in new applications ranging from spintronics to microelectronic devices. △ Less

Submitted 24 July, 2025; originally announced July 2025.

Dis-GEN: Disordered crystal structure generation

Authors: Martin Hoffmann Petersen, Ruiming Zhu, Haiwen Dai, Savyasanchi Aggarwal, Nong Wei, Andy Paul Chen, Arghya Bhowmik, Juan Maria Garcia Lastra, Kedar Hippalgaonkar

Abstract: A wide range of synthesized crystalline inorganic materials exhibit compositional disorder, where multiple atomic species partially occupy the same crystallographic site. As a result, the physical and chemical properties of such materials are dependent on how the atomic species are distributed among the corresponding symmetrical sites, making them exceptionally challenging to model using computati… ▽ More A wide range of synthesized crystalline inorganic materials exhibit compositional disorder, where multiple atomic species partially occupy the same crystallographic site. As a result, the physical and chemical properties of such materials are dependent on how the atomic species are distributed among the corresponding symmetrical sites, making them exceptionally challenging to model using computational methods. For this reason, existing generative models cannot handle the complexities of disordered inorganic crystals. To address this gap, we introduce Dis-GEN, a generative model based on an empirical equivariant representation, derived from theoretical crystallography methodology. Dis-GEN is capable of generating symmetry-consistent structures that accommodate both compositional disorder and vacancies. The model is uniquely trained on experimental structures from the Inorganic Crystal Structure Database (ICSD) - the world's largest database of identified inorganic crystal structures. We demonstrate that Dis-GEN can effectively generate disordered inorganic materials while preserving crystallographic symmetry throughout the generation process. This approach provides a critical check point for the systematic exploration and discovery of disordered functional materials, expanding the scope of generative modeling in materials science. △ Less

Submitted 24 July, 2025; originally announced July 2025.

Neural Network-Augmented Pfaffian Wave-functions for Scalable Simulations of Interacting Fermions

Authors: Ao Chen, Zhou-Quan Wan, Anirvan Sengupta, Antoine Georges, Christopher Roth

Abstract: Developing accurate numerical methods for strongly interacting fermions is crucial for improving our understanding of various quantum many-body phenomena, especially unconventional superconductivity. Recently, neural quantum states have emerged as a promising approach for studying correlated fermions, highlighted by the hidden fermion and backflow methods, which use neural networks to model correc… ▽ More Developing accurate numerical methods for strongly interacting fermions is crucial for improving our understanding of various quantum many-body phenomena, especially unconventional superconductivity. Recently, neural quantum states have emerged as a promising approach for studying correlated fermions, highlighted by the hidden fermion and backflow methods, which use neural networks to model corrections to fermionic quasiparticle orbitals. In this work, we expand these ideas to the space of Pfaffians, a wave-function that naturally expresses superconducting pairings, and propose the hidden fermion Pfaffian state (HFPS), which flexibly represents both unpaired and superconducting phases and scales to large systems with favorable asymptotic complexity. In our numerical experiments, HFPS provides state-of-the-art variational accuracy in different regimes of both the attractive and repulsive Hubbard models. We show that the HFPS is able to capture both s-wave and d-wave pairing, and therefore may be a useful tool for modeling phases with unconventional superconductivity. △ Less

Submitted 14 July, 2025; originally announced July 2025.

Reversible Modification of Rashba States in Topological Insulators at Room Temperature by Edge Functionalization

Authors: Wonhee Ko, Seoung-Hun Kang, Qiangsheng Lu, An-Hsi Chen, Gyula Eres, Ho Nyung Lee, Young-Kyun Kwon, Robert G. Moore, Mina Yoon, Matthew Brahlek

Abstract: Quantum materials with novel spin textures from strong spin-orbit coupling (SOC) are essential components for a wide array of proposed spintronic devices. Topological insulators have necessary strong SOC that imposes a unique spin texture on topological states and Rashba states that arise on the boundary, but there is no established methodology to control the spin texture reversibly. Here, we demo… ▽ More Quantum materials with novel spin textures from strong spin-orbit coupling (SOC) are essential components for a wide array of proposed spintronic devices. Topological insulators have necessary strong SOC that imposes a unique spin texture on topological states and Rashba states that arise on the boundary, but there is no established methodology to control the spin texture reversibly. Here, we demonstrate that functionalizing Bi2Se3 films by altering the step-edge termination directly changes the strength of SOC and thereby modifies the Rashba strength of 1D edge states. Scanning tunneling microscopy/spectroscopy shows that these Rashba edge states arise and subsequently vanish through the Se functionalization and reduction process of the step edges. The observations are corroborated by density functional theory calculations, which show that a subtle chemical change of edge termination fundamentally alters the underlying electronic structure. Importantly, we experimentally demonstrated fully reversible and repeatable switching of Rashba edge states across multiple cycles at room temperature. The results imply Se functionalization as a practical method to control SOC and spin texture of quantum states in topological insulators. △ Less

Submitted 9 July, 2025; originally announced July 2025.

Journal ref: Advanced Science (2025): e19814

Data-Driven Design-Test-Make-Analyze Paradigm for Inorganic Crystals: Ultrafast Synthesis of Ternary Oxides

Authors: Haiwen Dai, Matthew J. McDermott, Andy Paul Chen, Jose Recatala-Gomez, Wei Nong, Ruiming Zhu, Maung Thway, Samuel Morris, Christian Schürmann, Shreyas Dinesh Pethe, Chenguang Zhang, Wuan Geok Saw, Bich Ngoc Tran, Pritish Mishra, Fengxia Wei, Albertus Denny Handoko, Sabrine Hachmioune, Haipei Shao, Ming Lin, Chong Wai Liew, Kristin A. Persson, Kedar Hippalgaonkar

Abstract: Data-driven methodologies hold the promise of revolutionizing inorganic materials discovery, but they often face challenges due to discrepancies between theoretical predictions and experimental validation. In this work, we present an end-to-end discovery framework that leverages synthesizability, oxidation state probability, and reaction pathway calculations to guide the exploration of transition… ▽ More Data-driven methodologies hold the promise of revolutionizing inorganic materials discovery, but they often face challenges due to discrepancies between theoretical predictions and experimental validation. In this work, we present an end-to-end discovery framework that leverages synthesizability, oxidation state probability, and reaction pathway calculations to guide the exploration of transition metal oxide spaces. Two previously unsynthesized target compositions, ZnVO3 and YMoO3, passed preliminary computational evaluation and were considered for ultrafast synthesis. Comprehensive structural and compositional analysis confirmed the successful synthesis ZnVO3 in a partially disordered spinel structure, validated via Density Functional Theory (DFT). Exploration of YMoO3 led to YMoO3-x with elemental composition close to 1:1:3; the structure was subsequently identified to be Y4Mo4O11 through micro-electron diffraction (microED) analysis. Our framework effectively integrates multi-aspect physics-based filtration with in-depth characterization, demonstrating the feasibility of designing, testing, synthesizing, and analyzing (DTMA) novel material candidates, marking a significant advancement towards inorganic materials by design. △ Less

Submitted 23 June, 2025; originally announced June 2025.

Comments: related repo at https://github.com/Kedar-Materials-by-Design-Lab/Design-Test-Make-Analyze/

Neuralized Fermionic Tensor Networks for Quantum Many-Body Systems

Authors: Si-Jing Du, Ao Chen, Garnet Kin-Lic Chan

Abstract: We describe a class of neuralized fermionic tensor network states (NN-fTNS) that introduce non-linearity into fermionic tensor networks through configuration-dependent neural network transformations of the local tensors. The construction uses the fTNS algebra to implement a natural fermionic sign structure and is compatible with standard tensor network algorithms, but gains enhanced expressivity t… ▽ More We describe a class of neuralized fermionic tensor network states (NN-fTNS) that introduce non-linearity into fermionic tensor networks through configuration-dependent neural network transformations of the local tensors. The construction uses the fTNS algebra to implement a natural fermionic sign structure and is compatible with standard tensor network algorithms, but gains enhanced expressivity through the neural network parametrization. Using the 1D and 2D Fermi-Hubbard models as benchmarks, we demonstrate that NN-fTNS achieve order of magnitude improvements in the ground-state energy compared to pure fTNS with the same bond dimension, and can be systematically improved through both the tensor network bond dimension and the neural network parametrization. Compared to existing fermionic neural quantum states (NQS) based on Slater determinants and Pfaffians, NN-fTNS offer a physically motivated alternative fermionic structure. Furthermore, compared to such states, NN-fTNS naturally exhibit improved computational scaling and we demonstrate a construction that achieves linear scaling with the lattice size. △ Less

Submitted 28 October, 2025; v1 submitted 9 June, 2025; originally announced June 2025.

Comments: 6 pages, 5 figures + 7 pages, 5 figures

Transforming Acidic Corrosion and Embrittlement into a Hydrogen-Trapping Cage

Authors: Ankang Chen, Jiewen Liu, Zihao Huo, Chuang Liu, Yongming Sui, Xuan Liu, Qingkun Yuan, Yan Li, Guangtong Wang, Bao Yuan, Defang Duan, Gang Liu, Bo Zou

Abstract: The vision of a hydrogen economy demands efficient platforms to close the gap between sustainable proton sources and solid-state hydrogen carriers. Metal hydrides serve as key carriers, yet their synthesis remains constrained by the energy-intensive use of high-pressure H2, which fragments the hydrogen chain. Here, we overturn this paradigm by transforming two classic degradation mechanisms, acidi… ▽ More The vision of a hydrogen economy demands efficient platforms to close the gap between sustainable proton sources and solid-state hydrogen carriers. Metal hydrides serve as key carriers, yet their synthesis remains constrained by the energy-intensive use of high-pressure H2, which fragments the hydrogen chain. Here, we overturn this paradigm by transforming two classic degradation mechanisms, acidic corrosion and hydrogen embrittlement, into a constructive materials-design strategy. We demonstrate that synergistic control of these processes in acid enables the in-situ engineering of a "hydrogen-trapping cage" (HTC) microstructure within metals. Composed of a dense defect network, this cage directly captures and stabilizes protons as hydrides under mild conditions, guided by the universal criterion |DeltaPeq| > DeltaPph. Using this platform, we synthesize over 20 hydrides, including challenging targets such as LiH and NaH, and showcase its functional power with a cage-rich titanium hydride electrocatalyst. This catalyst achieves an exceptional current density of 1.07 A cm-2 for nitrate-to-ammonia conversion, attributed to rapid H- transport within the engineered cage. This work establishes a transformative "failure-to-function" paradigm, delivering an integrated platform that unifies hydrogen capture, stabilization, and conversion. △ Less

Submitted 5 January, 2026; v1 submitted 5 June, 2025; originally announced June 2025.

A planning tool for neutron powder diffraction experiments

Authors: Joseph A. M. Paddison, Stuart Calder, Danielle R. Yahne, Malcolm J. Cochran, Si Athena Chen, Matthias D. Frontzek, Yuanpeng Zhang

Abstract: We introduce a computer program to simulate the results of neutron powder-diffraction experiments at the High Flux Isotope Reactor at Oak Ridge National Laboratory. The program is freely available as a web application at http://addie.ornl.gov/hfirestimate, and is designed to be straightforward to use for researchers who are new to neutron diffraction. The input includes the crystal structure of th… ▽ More We introduce a computer program to simulate the results of neutron powder-diffraction experiments at the High Flux Isotope Reactor at Oak Ridge National Laboratory. The program is freely available as a web application at http://addie.ornl.gov/hfirestimate, and is designed to be straightforward to use for researchers who are new to neutron diffraction. The input includes the crystal structure of the proposed sample, the sample mass, and the instrument configuration. The results include a plot of the simulated data -- including realistic estimates of background and the error bars due to counting statistics -- and suggestions of how to resolve potential problems with the experiment. Here, we explain the design and implementation of this program and demonstrate its performance using comparisons of simulated and experimental data. We hope that this program will enable researchers to plan neutron-scattering experiments more effectively, increasing the likelihood of successful experiments and improving the productivity of neutron-diffraction research. △ Less

Submitted 2 June, 2025; originally announced June 2025.

Comments: 8 pages, 3 figures

Nucleation and Antiphase Twin Control in Bi$_2$Se$_3$ via Step-Terminated Al$_2$O$_3$ Substrates

Authors: Alessandro R. Mazza, Jia Shi, Gabriel A. Vázquez-Lizardi, Sangsoo Kim, Jackson Bentley, An-Hsi Chen, Kim Kisslinger, Debarghya Mallick, Qiangsheng Lu, T. Zac Ward, Vitalii Starchenko, Nicholas Cucciniello, Robert G. Moore, Gyula Eres, Yue Cao, Debangshu Mukherjee, Liam Collins, Christopher Nelson, Danielle Reifsnyder Hickey, Fei Xue, Matthew Brahlek

Abstract: The epitaxial synthesis of high-quality 2D layered materials is an essential driver of both fundamental physics studies and technological applications. Bi$_2$Se$_3$, a prototypical 2D layered topological insulator, is sensitive to defects imparted during the growth, either thermodynamically or due to the film-substrate interaction. In this study, it is shown that step-terminated Al$_2$O$_3$ substr… ▽ More The epitaxial synthesis of high-quality 2D layered materials is an essential driver of both fundamental physics studies and technological applications. Bi$_2$Se$_3$, a prototypical 2D layered topological insulator, is sensitive to defects imparted during the growth, either thermodynamically or due to the film-substrate interaction. In this study, it is shown that step-terminated Al$_2$O$_3$ substrates with a high miscut angle (3°) can effectively suppress a particular hard-to-mitigate defect, the antiphase twin. Systematic investigations across a range of growth temperatures and substrate miscut angles confirm that atomic step edges act as preferential nucleation sites, stabilizing a single twin domain. First-principles calculations suggest that there is a significant energy barrier for twin boundary formation at step edges, supporting the experimental observations. Detailed structural characterization indicates that this twin-selectivity is lost through the mechanism of the 2D layers overgrowing the step edges, leading to higher twin density as the thickness increases. These findings highlight the complex energy landscape unique to 2D materials that is driven by the interplay between substrate properties, nucleation dynamics, and defect formation, and overcoming and controlling these are critical to improve material quality for quantum and electronic applications. △ Less

Submitted 23 February, 2026; v1 submitted 23 May, 2025; originally announced May 2025.

Journal ref: Advanced Functional Materials, e13054 (2026)

Mechanics of three-dimensional micro-architected interpenetrating phase composites

Authors: Andrew Y. Chen, Carlos M. Portela

Abstract: Composite materials are used across engineering applications for their superior mechanical performance, a result of efficient load transfer between the structure and matrix phases. However, the inherently two-dimensional structure of laminated composites reduces their robustness to shear and out-of-plane loads, while unpredictable interlaminar failure and fiber pull-out can cause a catastrophic lo… ▽ More Composite materials are used across engineering applications for their superior mechanical performance, a result of efficient load transfer between the structure and matrix phases. However, the inherently two-dimensional structure of laminated composites reduces their robustness to shear and out-of-plane loads, while unpredictable interlaminar failure and fiber pull-out can cause a catastrophic loss of load capacity. Meanwhile, advances toward uncovering structure-property relations in architected materials have led to highly tunable mechanical properties, deformation, and even failure. Some of these architected materials have reached near-theoretical limits; however, the majority of current work focuses on describing the response of a single-material network in air, and the effect of adding a load-bearing second phase to a three-dimensional architecture is not well understood. Here, we develop facile fabrication methods for realizing centimeter-scale polymer- and carbon-based architected interpenetrating phase composite (IPC) materials, i.e., two-phase materials consisting of a continuous 3D architecture surrounded by a load-bearing matrix across length scales, and determine the effect of geometry and constituent material properties on the mechanics of these architected IPCs. Using these experiments together with computational models, we show that the matrix phase distributes stress effectively, resulting in a high-strength, stable response. Notably, failure delocalization enhances energy dissipation of the composite, achieving specific energy absorption (SEA) values comparable to those of wound fiber tubes. Finally, we demonstrate that the stress state in an IPC can be tuned using geometric design and introduce an example in an architected composite. Altogether, this work bridges the gap between mechanically efficient composites and tunable architected materials. △ Less

Submitted 22 May, 2025; originally announced May 2025.

Comments: 20 pages of main text, 6 figures, appendix

Terahertz Landau level spectroscopy of Dirac fermions in millimeter-scale twisted bilayer graphene

Authors: Benjamin F. Mead, Spenser Talkington, An-Hsi Chen, Debarghya Mallick, Zhaodong Chu, Xingyue Han, Seong-Jun Yang, Cheol-Joo Kim, Matthew Brahlek, Eugene J. Mele, Liang Wu

Abstract: Exotic electronic physics including correlated insulating states and fractional Chern insulators have been observed in twisted bilayer graphene in a magnetic field when the Fermi velocity vanishes, however a question remains as to the stability of these states which is controlled by the gap to the first excited state. Free-space terahertz magneto-optics can directly probe the gap to charge excitat… ▽ More Exotic electronic physics including correlated insulating states and fractional Chern insulators have been observed in twisted bilayer graphene in a magnetic field when the Fermi velocity vanishes, however a question remains as to the stability of these states which is controlled by the gap to the first excited state. Free-space terahertz magneto-optics can directly probe the gap to charge excitations which bounds the stability of electronic states, but this measurement has thus-far been inaccessible due to the micron size of twisted bilayer graphene samples, while the wavelength of terahertz light is up to a millimeter. Here we leverage advances in fabrication to create twisted bilayer graphene samples over 5 mm x 5 mm in size with a uniform twist angle and study the magnetic field dependence of the cyclotron resonance by a complex Faraday rotation experiment in p-doped large angle twisted bilayer graphene. These measurements directly probe charge excitations in inter-Landau level transitions and determine the Fermi velocity as a function of twist angle. △ Less

Submitted 15 October, 2025; v1 submitted 28 April, 2025; originally announced April 2025.

Comments: 7+2 pages, 4+2 figures; version accepted by Phys. Rev. B

Journal ref: Physical Review B 112, 205116 (2025)

Acoustic topological Jackiw-Rebbi states at symmetry broken interfaces

Authors: Yifei Xia, An Chen, Ting Zhang, Jing Yang, Bin Liang, Johan Christensen, Jianchun Cheng

Abstract: Topological insulators, a fundamental concept in modern condensed matter physics, support localized states at the interfaces between insulators exhibiting different topological phases, which conventionally rely on explicit symmetry breaking. Here, we propose a mechanism to induce a real-space topological phase transition by spontaneous symmetry breaking, thereby constructing an acoustic metagratin… ▽ More Topological insulators, a fundamental concept in modern condensed matter physics, support localized states at the interfaces between insulators exhibiting different topological phases, which conventionally rely on explicit symmetry breaking. Here, we propose a mechanism to induce a real-space topological phase transition by spontaneous symmetry breaking, thereby constructing an acoustic metagrating to generate nontrivial Jackiw-Rebbi states characterized by robust imaginary band degeneracy. Our experimental implementation verifies the acoustic delocalized interface state with a constant phase jump, demonstrating enhanced high-directivity topological radiation. We foresee that our findings may spark interest in engineering new acoustic topological devices. △ Less

Submitted 24 April, 2025; originally announced April 2025.

Orbital Current-Driven Magnetization Switching in a Magnetic Tunnel Junction

Authors: Jingkai Xu, Dongxing Zheng, Meng Tang, Chen Liu, Bin He, Man Yang, Hao Li, Yan Li, Aitian Chen, Senfu Zhang, Ziqiang Qiu, Xixiang Zhang

Abstract: Spin-orbitronics, based on both spin and orbital angular momentum, presents a promising pathway for energy-efficient memory and logic devices. Recent studies have demonstrated the emergence of orbital currents in light transition metals such as Ti, Cr, and Zr, broadening the scope of spin-orbit torque (SOT). In particular, the orbital Hall effect, which arises independently of spin-obit coupling,… ▽ More Spin-orbitronics, based on both spin and orbital angular momentum, presents a promising pathway for energy-efficient memory and logic devices. Recent studies have demonstrated the emergence of orbital currents in light transition metals such as Ti, Cr, and Zr, broadening the scope of spin-orbit torque (SOT). In particular, the orbital Hall effect, which arises independently of spin-obit coupling, has shown potential for enhancing torque efficiency in spintronic devices. However, the direct integration of orbital current into magnetic random-access memory (MRAM) remains unexplored. In this work, we design a light metal/heavy metal/ferromagnet multilayer structure and experimentally demonstrate magnetization switching by orbital current. Furthermore, we have realized a robust SOT-MRAM cell by incorporating a reference layer that is pinned by a synthetic antiferromagnetic structure. We observed a tunnel magnetoresistance of 66%, evident in both magnetic field and current-driven switching processes. Our findings underscore the potential for employing orbital current in designing next-generation spintronic devices. △ Less

Submitted 3 December, 2025; v1 submitted 8 April, 2025; originally announced April 2025.

Manipulating magnetization by orbital current from a light metal Ti

Authors: Dongxing Zheng, Jingkai Xu, Fatimah Alsayafi, Sachin Krishnia, Dongwook Go, Duc Tran, Tao Yang, Yan Li, Yinchang Ma, Chen Liu, Meng Tang, Aitian Chen, Hanin Algaidi, Hao Wu, Kai Liu, Yuriy Mokrousov, Mathias Kläui, Udo Schwingenschlögl, Xixiang Zhang

Abstract: The orbital Hall effect, which does not rely on the spin-orbit coupling, has recently emerged as a promising mechanism for electrically manipulating magnetization in thin-film ferromagnets. Despite its potential, direct experimental observation of magnetization switching driven by orbital currents has been challenging, primarily because there is no direct exchange coupling between orbital angular… ▽ More The orbital Hall effect, which does not rely on the spin-orbit coupling, has recently emerged as a promising mechanism for electrically manipulating magnetization in thin-film ferromagnets. Despite its potential, direct experimental observation of magnetization switching driven by orbital currents has been challenging, primarily because there is no direct exchange coupling between orbital angular momentum and local spin based magnetic moments. In this study, we present a compensated design to directly probe the contribution of orbital currents in the most promising light metal titanium (Ti), where symmetric layer structures allow zeroing out of the net spin current. By varying the thickness of the Ti layer in Ti(t)/Pt/Co/Pt/Co/Pt multilayers, we demonstrate the ability to control the magnetization switching polarity. We deduce the orbital charge conversion efficiency of the Ti layer to be approximately 0.17. These findings not only confirm the presence of the orbital Hall effect in Ti but also suggest that orbital currents may be promising candidates for developing energy-efficient magnetic devices with enhanced performance and scalability. △ Less

Submitted 6 April, 2025; originally announced April 2025.

Sn-InAs nanowire shadow-defined Josephson junctions

Authors: Amritesh Sharma, An-Hsi Chen, Connor P. Dempsey, Amrita Purkayastha, Mihir Pendharkar, Susheng Tan, Christopher J. Palmstrøm, Sergey M. Frolov, Moïra Hocevar

Abstract: Interest in hybrid electronic devices for quantum science is driving the research into superconductor-semiconductor materials combinations. Here we study InAs nanowires coated with shells of $β$-Sn. The wires grow via the vapor-liquid-solid mechanism out from (001) InAs substrates along two orientations, forming a criss-crossing landscape. This allows us to define nanowire-shadow junctions during… ▽ More Interest in hybrid electronic devices for quantum science is driving the research into superconductor-semiconductor materials combinations. Here we study InAs nanowires coated with shells of $β$-Sn. The wires grow via the vapor-liquid-solid mechanism out from (001) InAs substrates along two orientations, forming a criss-crossing landscape. This allows us to define nanowire-shadow junctions during the low temperature Sn shell deposition by carefully choosing the deposition angle. We find that the Sn shells are uniform in thickness and the grains have a preferential in-plane epitaxial relationship with InAs. The interface between Sn and InAs is abrupt and we do not observe interdiffusion. In our nanowire devices, Sn induces a superconducting gap of order 600 $μ$eV, switching currents reaching values up to 500 nA, and critical magnetic fields along the nanowire of up to 1.3 T. These characteristics can be leveraged in the design of superconducting transmon qubits, parametric microwave amplifiers as well as for the investigation of triplet and topological superconductivity. △ Less

Submitted 17 March, 2025; originally announced March 2025.

Comments: 12 pages, 6 figures, included SI (12 pages, 12 figures)

Quantized Magneto-Terahertz Effects in the Antiferromagnetic Topological Insulator MnBi$_2$Te$_4$ Thin Films

Authors: Xingyue Han, An-Hsi Chen, Matthew Brahlek, Liang Wu

Abstract: MnBi$_2$Te$_4$ (MBT) is an ideal platform for studying the interplay between magnetism and topology. Many exotic topological phenomena, such as the quantum anomalous Hall effect and the axion insulator, have been observed in few-layer MBT. A key feature in MBT is the emergence of the surface exchange gap, which lies in the milli-electron-volt range (1 THz corresponds to 4.14 meV). This makes THz s… ▽ More MnBi$_2$Te$_4$ (MBT) is an ideal platform for studying the interplay between magnetism and topology. Many exotic topological phenomena, such as the quantum anomalous Hall effect and the axion insulator, have been observed in few-layer MBT. A key feature in MBT is the emergence of the surface exchange gap, which lies in the milli-electron-volt range (1 THz corresponds to 4.14 meV). This makes THz spectroscopy a powerful tool to probe the associated topological physics. In this study, we report the THz spectra of Faraday and Kerr rotations in MBT thin films grown by molecular beam epitaxy. By varying the external magnetic field, we observe three magnetic states: the antiferromagnetic state, the canted antiferromagnetic state, and the ferromagnetic state. Our terahertz results show a quantized Hall state under 6 T in both 6 SL and 7 SL samples without gate voltage. These findings provide new insights into the magneto-terahertz properties of MBT and its potential for topological spintronic applications. △ Less

Submitted 18 March, 2025; v1 submitted 17 March, 2025; originally announced March 2025.

Convolutional transformer wave functions

Authors: Ao Chen, Vighnesh Dattatraya Naik, Markus Heyl

Abstract: Deep neural quantum states have recently achieved remarkable performance in solving challenging quantum many-body problems. While transformer networks appear particularly promising due to their success in computer science, we show that previously reported transformer wave functions haven't so far been capable to utilize their full power. Here, we introduce the convolutional transformer wave functi… ▽ More Deep neural quantum states have recently achieved remarkable performance in solving challenging quantum many-body problems. While transformer networks appear particularly promising due to their success in computer science, we show that previously reported transformer wave functions haven't so far been capable to utilize their full power. Here, we introduce the convolutional transformer wave function (CTWF). We show that our CTWFs exhibit superior performance in ground-state search and non-equilibrium dynamics compared to previous results, demonstrating promising capacity in complex quantum problems. △ Less

Submitted 13 March, 2025; originally announced March 2025.

Generalized Peierls substitution for Wannier obstructions: response to disorder and interactions

Authors: Shuai A. Chen, Roderich Moessner, Tai Kai Ng

Abstract: We study the interplay between quantum geometry, interactions, and external fields in complex band systems. When Wannier obstructions preclude a description based solely on atomic-like orbitals, this complicates the prediction of electromagnetic responses particularly in the presence of disorder and interactions. In this work, we introduce a generalized Peierls substitution framework based on Lagr… ▽ More We study the interplay between quantum geometry, interactions, and external fields in complex band systems. When Wannier obstructions preclude a description based solely on atomic-like orbitals, this complicates the prediction of electromagnetic responses particularly in the presence of disorder and interactions. In this work, we introduce a generalized Peierls substitution framework based on Lagrange multipliers to enforce the constraints of the Wannier obstruction in the band of interest. Thus we obtain effective descriptions of interactions and disorder in the presence of non-trivial quantum geometry of that band. We apply our approach to examples including the diamagnetic response in flat-band superconductors and delocalization effects in flat-band metals caused by interactions and disorder. △ Less

Submitted 25 September, 2025; v1 submitted 12 March, 2025; originally announced March 2025.

Comments: Published version and comments are welcome

Single-layer magnet phase in intrinsic magnetic topological insulators, $[\mathrm{MnTe}][\mathrm{Bi}_{2}\mathrm{Te}_{3}]_{\mathrm{n}}$, far beyond the thermodynamic limit

Authors: Deepti Jain, Hee Taek Yi, Xiong Yao, Alessandro R. Mazza, An-Hsi Chen, Kim Kisslinger, Myung-Geun Han, Matthew Brahlek, Seongshik Oh

Abstract: The intrinsic magnetic topological insulator (IMTI) family $[\mathrm{MnTe}][\mathrm{Bi}_{2}\mathrm{Te}_{3}]_{\mathrm{n}}$ has demonstrated magneto-topological properties dependent on $n$, making it a promising platform for advanced electronics and spintronics. However, due to technical barriers in sample synthesis, their properties in the large $n$ limit remain unknown. To overcome this, we utiliz… ▽ More The intrinsic magnetic topological insulator (IMTI) family $[\mathrm{MnTe}][\mathrm{Bi}_{2}\mathrm{Te}_{3}]_{\mathrm{n}}$ has demonstrated magneto-topological properties dependent on $n$, making it a promising platform for advanced electronics and spintronics. However, due to technical barriers in sample synthesis, their properties in the large $n$ limit remain unknown. To overcome this, we utilized the atomic layer-by-layer molecular beam epitaxy (ALL-MBE) technique and achieved IMTIs with $n$ as large as 15, far beyond the previously reported in bulk crystals or thin films. Then, we discover that the "single-layer magnet (SLM)" phase, primarily determined by intralayer ferromagnetic coupling, emerges for $n >$ $\sim 4$ and remains little affected up to $n = 15$. Nonetheless, still, non-zero, interlayer ferromagnetic coupling is necessary to stabilize the SLM phase, suggesting that the SLM phase eventually disappears in the $n\to\infty$ limit. This study uncovers the secrets of IMTIs beyond the thermodynamic limit and opens a door to diverse magneto-topological applications. △ Less

Submitted 8 March, 2025; originally announced March 2025.

Spin correlations in La$_3$Ni$_2$O$_7$ superconducting thin films

Authors: Hengyang Zhong, Bo Hao, Zhijia Zhang, Anni Chen, Yuan Wei, Ruixian Liu, Xinru Huang, Chunyi Li, Wenting Zhang, Chang Liu, Xiao-Sheng Ni, Marli dos Reis Cantarino, Kurt Kummer, Nicholas Brookes, Kun Cao, Yuefeng Nie, Thorsten Schmitt, Xingye Lu

Abstract: The discovery of ambient-pressure superconductivity with $T_{c,\text{onset}} > 40$ K in {\LNO} (LNO) thin films grown on the SrLaAlO$_4$ (SLAO) substrate with compressive ($\varepsilon\approx-2\%$) epitaxial strain provides a unique platform for investigating the superconducting mechanisms in nickelate superconductors. Here, we use resonant inelastic X-ray scattering (RIXS) to unveil the dispersiv… ▽ More The discovery of ambient-pressure superconductivity with $T_{c,\text{onset}} > 40$ K in {\LNO} (LNO) thin films grown on the SrLaAlO$_4$ (SLAO) substrate with compressive ($\varepsilon\approx-2\%$) epitaxial strain provides a unique platform for investigating the superconducting mechanisms in nickelate superconductors. Here, we use resonant inelastic X-ray scattering (RIXS) to unveil the dispersive spin excitations in the LNO/SLAO superconducting thin film and establish the strain dependence of the electronic and spin excitations in LNO thin films with strain ranging from $\varepsilon\approx-2\%$ to $+1.9\%$. Compared with the bulk crystal, the LNO/SLAO thin film (with $\varepsilon\approx-2\%$) exhibits similar $dd$ excitations and spin dynamics with larger bandwidth. By contrast, tensile-strained LNO/SrTiO$_3$ ($\varepsilon \approx +1.9\%$) exhibits a marked suppression of both the spin excitations and the Ni 3{\dz}-derived $dd$ excitations. The strain dependence of the spin excitations reflects significant changes in the interlayer exchange coupling $J_z$, and the diminishing $dd$ excitations in tensile-strained samples indicate weaker Ni 3{\dz}-O 2$p_{z}$ hybridization. This strain evolution of the spin excitations and $J_z$ is attributed to the strain-tuned $c$-axis Ni-O-Ni bond angle $\varphi$, which controls the Ni 3{\dz}-O 2$p_{z}$ hybridization. Since superconductivity is observed only in films grown on SLAO, and spin correlations are enhanced along with the emergence of superconductivity, our results identify $\varphi$ as a key structural lever controlling $J_z$ and provide direct spectroscopic support for interlayer spin-fluctuation-mediated pairing scenarios in bilayer nickelates. △ Less

Submitted 16 November, 2025; v1 submitted 5 February, 2025; originally announced February 2025.

Comments: 7 pages, 4 figures. Supplementary is available upon reasonable request

Universal Superconductivity in FeTe and All-Iron-Based Ferromagnetic Superconductor Heterostructures

Authors: Hee Taek Yi, Xiong Yao, Deepti Jain, Ying-Ting Chan, An-Hsi Chen, Matthew Brahlek, Kim Kisslinger, Kai Du, Myung-Geun Han, Yimei Zhu, Weida Wu, Sang-Wook Cheong, Seongshik Oh

Abstract: Ferromagnetism (FM) and superconductivity (SC) are two of the most famous macroscopic quantum phenomena. However, nature normally does not allow SC and FM to coexist without significant degradation. Here, we introduce the first fully iron-based SC/FM heterostructures, composed of Fe(Te,Se) and Fe3GeTe2, and show that in this platform strong FM and high-temperature SC robustly coexist. We subsequen… ▽ More Ferromagnetism (FM) and superconductivity (SC) are two of the most famous macroscopic quantum phenomena. However, nature normally does not allow SC and FM to coexist without significant degradation. Here, we introduce the first fully iron-based SC/FM heterostructures, composed of Fe(Te,Se) and Fe3GeTe2, and show that in this platform strong FM and high-temperature SC robustly coexist. We subsequently discover that chemical proximity effect from neighboring layers can universally drive the otherwise non-superconducting FeTe films into a SC state. This suggests that the ground state of FeTe is so close to the SC state that it could be driven in and out of the SC state with various other perturbations. Altogether, this shows that Fe-Te-based heterostructures provide a unique opportunity to manipulate magnetism, superconductivity and topological physics, paving the way toward new superconducting technologies. △ Less

Submitted 3 February, 2025; originally announced February 2025.

Journal ref: Adv. Funct. Mater. 2025, 2418259

The shape of cleaved tethered membranes

Authors: A. D. Chen, M. C. Gandikota, A. Cacciuto

Abstract: A remarkable property of flexible self-avoiding elastic surfaces (membranes) is that they remain flat at all temperatures, even in the absence of a bending rigidity or in the presence of active fluctuations. Here, we report numerical results of these surfaces wherein we alter their topology by systematically cleaving internal bonds. While it is known that a random removal of membrane bonds does no… ▽ More A remarkable property of flexible self-avoiding elastic surfaces (membranes) is that they remain flat at all temperatures, even in the absence of a bending rigidity or in the presence of active fluctuations. Here, we report numerical results of these surfaces wherein we alter their topology by systematically cleaving internal bonds. While it is known that a random removal of membrane bonds does not disrupt the overall extended shape of the membrane, we find that cleaving an elastic surface with longitudinal parallel cuts leads to its systematic collapse into a number of complex morphologies that can be controlled by altering the number and length of the inserted cuts. For the simpler case of membranes with bending rigidity but in the absence of self-avoidance, we find that the radius of gyration of the surface as a function of number of cuts is represented by a universal master curve when the variables are appropriately rescaled. △ Less

Submitted 13 January, 2025; originally announced January 2025.

Comments: 8 pages, 5 figures

Molecular HDD Logic for Encrypted Massive Data Storage

Authors: Bingjie Guo, Xinhui Chen, An Chen, Jinxin Wang, Wuhong Xue, Tao Wang, Zhixin Wu, Xiaolong Zhong, Jianmin Zeng, Jinjin Li, Mao Li, Xiaohong Xu, Yu Chen, Gang Liu

Abstract: Organic memories, with small dimension, fast speed and long retention features, are considered as promising candidates for massive data archiving. In order to satisfy the re-quirements for ultra-low power and high-security information storage, we design a concep-tual molecular hard-disk (HDD) logic scheme that is capable to execute in-situ encryption of massive data in pW/bit power-consumption ran… ▽ More Organic memories, with small dimension, fast speed and long retention features, are considered as promising candidates for massive data archiving. In order to satisfy the re-quirements for ultra-low power and high-security information storage, we design a concep-tual molecular hard-disk (HDD) logic scheme that is capable to execute in-situ encryption of massive data in pW/bit power-consumption range. Beneficial from the coupled mechanism of counter-balanced redox reaction and local ion drifting, the basic HDD unit consisting of ~ 200 self-assembled RuXLPH molecules in a monolayer (SAM) configuration undergoes unique conductance modulation with continuous, symmetric and low-power switching char-acteristics. 96-state memory performance, which allows 6-bit data storage and single-unit one-step XOR operation, is realized in the RuXLPH SAM sample. Through single-unit XOR manipulation of the pixel information, in-situ bitwise encryption of the Mogao Grottoes mural images stored in the molecular HDD is demonstrated. △ Less

Submitted 8 January, 2025; originally announced January 2025.