Showing 1–50 of 166 results for author: Liang, S

Room-temperature ferroelectrically switchable quantum geometry in few-layer WTe2 for complementary in-memory computing

Authors: Ruihan Wang, Pengfei Wang, Haoyun Chen, Yunze Peng, Bingyan Liu, Junlin Xiong, Xueyuan Zhang, Chen Pan, Xin Chen, Shengyuan A. Yang, Shi-Jun Liang, Feng Miao, Peng Song

Abstract: Quantum geometry, describing the inherent geometric structure of electron wavefunctions in momentum space, transcends the traditional charge degree of freedom and provides a novel physical basis for information encoding and processing. The key to such new computing paradigms is the non-volatile electrical programming of quantum geometric states at room temperature, which, however, has not been est… ▽ More Quantum geometry, describing the inherent geometric structure of electron wavefunctions in momentum space, transcends the traditional charge degree of freedom and provides a novel physical basis for information encoding and processing. The key to such new computing paradigms is the non-volatile electrical programming of quantum geometric states at room temperature, which, however, has not been established. Here, we demonstrate ferroelectrically switchable quantum geometry in few-layer WTe2, which uniquely enables complementary convolutional processing. By employing the intrinsic coupling between ferroelectric polarization and quantum geometry in few-layer WTe2, we show that the second- and third-order nonlinear anomalous Hall effects (NLAHE) can be deterministically and electrically switched in a nonvolatile and correlated manner. The switching is robust at room temperature for ~104 cycles and retention of ~105 s. Furthermore, leveraging the opposite switching behaviors of second- and third-order NLAHE at room temperature, we demonstrate complementary in-memory computing and implement a hardware-level complementary convolution kernel. This kernel overcomes the inherent directional specificity of conventional convolutional networks and achieves a texture recognition accuracy of 98%, thereby illustrating a viable pathway towards physics-native computing through exploiting exotic physics in quantum materials. △ Less

Submitted 18 August, 2026; originally announced August 2026.

Comments: 4 Figures

Journal ref: Nature Communications, 2026,

Exact First-Passage Time Response Theory from Steady-State Response

Authors: Ruicheng Bao, Shiling Liang

Abstract: The mean first-passage time (MFPT) provides a universal temporal measure of transport, reaction, search, and switching processes in physical, chemical, and biological systems. Understanding how MFPTs respond to perturbations is therefore crucial for prediction and control, yet a systematic theory has been lacking. We establish a compact theoretical framework for linear and nonlinear MFPT response… ▽ More The mean first-passage time (MFPT) provides a universal temporal measure of transport, reaction, search, and switching processes in physical, chemical, and biological systems. Understanding how MFPTs respond to perturbations is therefore crucial for prediction and control, yet a systematic theory has been lacking. We establish a compact theoretical framework for linear and nonlinear MFPT response in continuous-time Markov processes. The key tool is an exact correspondence that maps the intrinsically transient response of MFPTs onto the steady-state response of an auxiliary system. This correspondence yields exact and universal response relations for MFPTs between arbitrary state pairs, expressed entirely in terms of unperturbed MFPTs and steady-state probabilities. We then obtain a factorized physical decomposition of the MFPT response into linear upstream, linear downstream, and nonlinear contributions. Further corollaries include response-curve inference rules, fundamental bounds on MFPT responses, analytical expressions for higher-order responses of MFPTs and steady-state probabilities, and multi-rate response formulas. Additionally, our result offers computational advantages in calculating both MFPTs and steady-state distributions. Finally, a biologically motivated folding network is analyzed, and a recently reported paradox on MFPT is clarified. △ Less

Submitted 11 August, 2026; originally announced August 2026.

Comments: 7+10 pages, 3 figures. See also our companion paper [arXiv:2608.06368]

A Universal Control Budget for First-Passage Kinetics

Authors: Shiling Liang, Ruicheng Bao

Abstract: The first-passage time is the natural observable of reaction completion, yet how its mean responds to a rate change has lacked a general constraint. We show that the logarithmic sensitivity of the mean first-passage time of any finite Markov chain to any rate is bounded by one in magnitude, and that these sensitivities sum to -1. Together the two laws form a conserved control budget: speeding comp… ▽ More The first-passage time is the natural observable of reaction completion, yet how its mean responds to a rate change has lacked a general constraint. We show that the logarithmic sensitivity of the mean first-passage time of any finite Markov chain to any rate is bounded by one in magnitude, and that these sensitivities sum to -1. Together the two laws form a conserved control budget: speeding completion through some transitions must be paid for by others, and a coordinated change shifts the completion time only as far as the budget allows. Raising an activation barrier or shifting the depth of a well moves many rates at once, yet neither can shift the completion time further than a single rate could. The budget caps kinetic-proofreading discrimination at the checkpoint count, and prices it in sensitivity to substrate concentration. △ Less

Submitted 11 August, 2026; v1 submitted 6 August, 2026; originally announced August 2026.

Comments: 8 pages, 4 figures. See also our companion letter [arXiv:2608.11202] for an exact and nonlinear response theory

Topological magnon noises

Authors: Shuang Liang, Tengyue Zhao, Yu-Hang Li, Hua Jiang

Abstract: We develop a comprehensive formalism for magnon transport in ferromagnetic insulators driven by a temperature gradient. The formulas for magnon current and corresponding magnon noise are derived herein based on the spin Hamiltonian of a topological magnon insulator, which enables us to calculate the magnon Hall angle, to provide an explicit expression for the Fano factor, and to reaffirm the quant… ▽ More We develop a comprehensive formalism for magnon transport in ferromagnetic insulators driven by a temperature gradient. The formulas for magnon current and corresponding magnon noise are derived herein based on the spin Hamiltonian of a topological magnon insulator, which enables us to calculate the magnon Hall angle, to provide an explicit expression for the Fano factor, and to reaffirm the quantitative relations between magnon conductance and magnon noise. We find that the magnon current is not conserved in the presence of the Gilbert damping. Consequently, the reciprocal relation between the local and nonlocal noises, the Johnson-Nyquist formula between the conductance and the thermal noise, and the relation between the transmission coefficient and the shot noise are profoundly altered. △ Less

Submitted 17 July, 2026; originally announced July 2026.

MatPhaseBench: A Semantics-Guided Benchmark for Materials Phase Diagrams Understanding

Authors: Hanwen Wang, Sihan Liang, Zhiwei Liu, Yangang Wang, Wei Yan, Yuqin Liu, Zongguo Wang

Abstract: Materials phase diagrams are a core knowledge representation in materials science, encoding temperature,composition, phase stability, and phase transformation pathways, with their full understanding requiring thermodynamic mechanism analysis and scientific reasoning. Although VLMs have shown promise in scientific image understanding, their systematic evaluation on such logically complex images dem… ▽ More Materials phase diagrams are a core knowledge representation in materials science, encoding temperature,composition, phase stability, and phase transformation pathways, with their full understanding requiring thermodynamic mechanism analysis and scientific reasoning. Although VLMs have shown promise in scientific image understanding, their systematic evaluation on such logically complex images demanding deep mechanistic interpretation remains limited, and phase diagrams provide a challenging testbed for this purpose. We introduce MatPhaseBench, a high-quality, high-reliability benchmark for complex scientific image understanding, focused on materials phase diagrams. MatPhaseBench is constructed from 3681 papers in classical materials science journals, from which 200 high-quality diagram-text pairs were selected, covering 189 material systems and 70 elements. The benchmark has three key features: (1)targeting complex scientific image understanding-it moves beyond simple objective tests to open-ended tasks requiring deep comprehension; (2)comprehensive image-text alignment-semantic information associated with images is fully preserved during literature mining and matching; (3) high-quality human-supervised text acquisition-all descriptions undergo strict manual validation. Experimental results show that current VLMs remain substantially behind expert-level understanding: they are largely limited to surface visual perception, lack deep reasoning grounded in thermodynamic mechanisms, have limited domain awareness and expert analytical experience, and perform poorly in distinguishing fine-grained differences in composite or multi-diagram settings. Overall, MatPhaseBench constitutes a challenging research-grade benchmark, providing a foundational platform for complex scientific image understanding, phase diagram analysis, and trustworthy multi-modal AI in science. △ Less

Submitted 3 July, 2026; originally announced July 2026.

Orientation-tunable correlated Chern insulating states in chiral twisted double bilayer graphene proximitized by WSe2

Authors: Jiao Xie, Yongqin Xie, Fanqiang Chen, Jiliang Yang, Sicheng Chen, Moyu Chen, Kenji Watanabe, Takashi Taniguchi, Shi-Jun Liang, Kemi Xu, Bin Cheng, Feng Miao

Abstract: Moire flat bands in graphene systems proximitized by transition-metal dichalcogenides (TMDCs) provide a setting where spin-orbit coupling (SOC) can reshape band topology. The crystallographic alignment angle twist angle between TMDC and graphene layers is predicted to tune the balance of Ising and Rashba SOC, but a combined theoretical and experimental understanding of how twist angle governs the… ▽ More Moire flat bands in graphene systems proximitized by transition-metal dichalcogenides (TMDCs) provide a setting where spin-orbit coupling (SOC) can reshape band topology. The crystallographic alignment angle twist angle between TMDC and graphene layers is predicted to tune the balance of Ising and Rashba SOC, but a combined theoretical and experimental understanding of how twist angle governs the topological character of correlated states has not been systematically established. Here we show that in chiral-stacked twisted double bilayer graphene in proximity to WSe2, twist angle between graphene and WSe2 determines the topological character of correlated Chern insulators. Continuum model calculations reveal that Ising spin-orbit coupling dominates at zero twist angle, giving rise to flat bands with finite valley Chern numbers, whereas Rashba coupling dominates at larger twist angle, resulting in topologically trivial bands. Transport measurements at quarter filling confirm this picture: twist angle = 0 deg devices exhibit C = +1 Chern insulators, consistent with spontaneous isospin polarization, whereas twist angle = 15 degree devices show C = 0 despite exhibiting similar correlated insulating behavior. The sharp contrast establishes crystallographic alignment as a new tuning knob, complementary to twist angle, displacement field, and carrier density, for engineering correlated topological states in van der Waals heterostructures. △ Less

Submitted 30 June, 2026; originally announced June 2026.

Tunable Extended Magnetic Non-Fermi Liquid in Graphene Moiré Heterostructures

Authors: Yongqin Xie, Jian Wang, Moyu Chen, Chen Zhao, Fanqiang Chen, Qiao Li, Sicheng Chen, Jiao Xie, Kenji Watanabe, Takashi Taniguchi, Jin-hua Gao, Rui Wang, Shi-Jun Liang, Chunming Yin, Bin Cheng, Feng Miao

Abstract: Exploring exotic quantum metallic states beyond Landau's Fermi liquid theory remains a central focus in condensed matter physics. Such non-Fermi liquid behavior is mostly observed near quantum criticality, yet growing attention is directed toward extended NFL phases with intrinsic quantum fluctuations rooted in the extended ground state. While these extended NFL states have been previously reporte… ▽ More Exploring exotic quantum metallic states beyond Landau's Fermi liquid theory remains a central focus in condensed matter physics. Such non-Fermi liquid behavior is mostly observed near quantum criticality, yet growing attention is directed toward extended NFL phases with intrinsic quantum fluctuations rooted in the extended ground state. While these extended NFL states have been previously reported only in a limited set of d- and f-electron systems, realizing a single, highly tunable platform capable of exhibiting multiple resistance exponent values is essential for uncovering the connection between the resistance exponent and the dominant quantum fluctuations coupled to quasiparticles. However, corresponding experimental progress remains elusive. Here, we report the observation of tunable extended non-Fermi liquid behavior in twisted double bilayer graphene encapsulated by aligned hBN layers. This NFL phase spans a broad range of carrier densities and exhibiting a carrier density dependent resistance exponent. Combined with temperature dependent resistance, magnetotransport and differential resistance measurements, these findings support a scenario where strong quantum fluctuations emerge from the interplay between localized and itinerant carriers. Our work establishes a highly tunable platform beyond conventional frameworks to investigate the organizing principles of non-Fermi liquid physics manifested in diverse behaviors. △ Less

Submitted 29 June, 2026; originally announced June 2026.

Epitaxial Strain Activates Altermagnetic Spin-Splitting Torques in RuO2(100)

Authors: Qi Jia, Seung Gyo Jeong, Seungjun Lee, Denis Tonini, Anand Santhosh, Yifei Yang, Xiangrui Li, Brahmdutta Dixit, Shuang Liang, Yu-Chia Chen, Tony Low, Bharat Jalan, Jian-Ping Wang

Abstract: The altermagnetic nature of rutile RuO2 remains under active debate: bulk measurements indicate a nearly nonmagnetic ground state, whereas thin-film studies have reported symmetry-dependent transport signatures consistent with altermagnetism. Here, we provide experimental evidence that altermagnetic spin splitting in RuO2 is a strain-stabilized emergent state rather than an intrinsic bulk property… ▽ More The altermagnetic nature of rutile RuO2 remains under active debate: bulk measurements indicate a nearly nonmagnetic ground state, whereas thin-film studies have reported symmetry-dependent transport signatures consistent with altermagnetism. Here, we provide experimental evidence that altermagnetic spin splitting in RuO2 is a strain-stabilized emergent state rather than an intrinsic bulk property. Angular-resolved spin-torque measurements reveal a symmetry-selected spin Hall response characteristic of altermagnetic spin splitting, which is strongest in the strained regime but progressively suppressed as the lattice relaxes toward the bulk limit. Complementary magnetic measurements further reveal enhanced coercivity and exchange-bias behavior exclusively in strained films, indicating the emergence of a strain-stabilized magnetic state. First-principles calculations reproduce the strain-dependent evolution of the Neel order and spin-split electronic structure, supporting the experimental observations. Together, these results establish altermagnetic spin splitting in RuO2 as a strain-stabilized emergent state and provide a unified explanation for the long-standing discrepancy between bulk and thin-film observations. △ Less

Submitted 24 June, 2026; originally announced June 2026.

20 Second Parity Lifetime in an InAs--Pb Tetron Device

Authors: Morteza Aghaee, Zulfi Alam, Mariusz Andrzejczuk, Andrey Antipov, Theodora Asimakidis, Mikhail Astafev, Lukas Avilovas, Ahmad Azizimanesh, Amin Barzegar, Bela Bauer, Jonathan Becker, Umesh Kumar Bhaskar, Andrea G. Boa, Srini Boddapati, Nichlaus Bohac, Jouri Bommer, Jan Borovsky, Léo Bourdet, Samuel Boutin, Srivatsa Chakravarthi, Benjamin J. Chapman, Nikolaos Chatzaras, Tzu-Chiao Chien, Jason Cho, Patrick T. Codd , et al. (140 additional authors not shown)

Abstract: A central promise of topological quantum computing is that increasing the excitation gap improves device performance significantly. Here, we experimentally validate this principle in an InAs--Pb tetron device via interferometric single-shot parity measurements. By replacing aluminum with the higher-gap superconductor lead in our superconductor-semiconductor hybrid devices, we have improved the rob… ▽ More A central promise of topological quantum computing is that increasing the excitation gap improves device performance significantly. Here, we experimentally validate this principle in an InAs--Pb tetron device via interferometric single-shot parity measurements. By replacing aluminum with the higher-gap superconductor lead in our superconductor-semiconductor hybrid devices, we have improved the robustness of our topological phase. In addition, to enable fast and precise bring-up at scale, we have developed an rf measurement technique that resolves low-energy wire-end states and directly measures their energy splitting with $μ\text{eV}$ precision. We employ this technique to bring up a device in a multi-tetron array and perform parity measurements of one of the tetron's hybrid nanowires (NWs). By controllably switching the wire parity, we observe $h/2e$-periodic bimodal shifts in the quantum capacitance of a quantum dot coupled to the hybrid nanowire in an interference loop. Further time-resolved measurements reveal a characteristic parity switching time of $\sim 20$ s with some instances reaching minute-scale. Such extremely long parity lifetimes are orders of magnitude longer than typical qubit operation times, which are on the order of $μ\text{s}$. Finally, we discuss potential implications for the fidelity of Pauli measurements. △ Less

Submitted 2 June, 2026; v1 submitted 2 June, 2026; originally announced June 2026.

Complementary-polarity double-layer LiTaO3 resonators for symmetry-selective SH2 excitation with ultrahigh electromechanical coupling (kt^2 = 25.7%)

Authors: Hao Yan, Zhen-hui Qin, Zhi-Wen Wang, Shu-Mao Wu, Chen-Bei Hao, Hua-Yang Chen, Sheng-Nan Liang, Ke Chen, Si-Yuan Yu, Yan-Feng Chen

Abstract: We report a structurally simple double-layer lithium tantalate (LiTaO3) bulk acoustic resonator that enables symmetry-selective excitation of the second-order thickness-shear (SH2) mode with ultrahigh electromechanical coupling. Two 31 deg Y-oriented single-crystal LiTaO3 films are rotation-bonded with complementary polarization (+X/-X) and driven by a longitudinal electric field. Matching between… ▽ More We report a structurally simple double-layer lithium tantalate (LiTaO3) bulk acoustic resonator that enables symmetry-selective excitation of the second-order thickness-shear (SH2) mode with ultrahigh electromechanical coupling. Two 31 deg Y-oriented single-crystal LiTaO3 films are rotation-bonded with complementary polarization (+X/-X) and driven by a longitudinal electric field. Matching between the effective piezoelectric symmetry and the SH2 mode yields an effective electromechanical coupling coefficient of kt^2 = 25.7% at 5.24 MHz. To our knowledge, this is the highest kt^2 reported for a LiTaO3 resonator architecture to date. The measured response is dominated by the target SH2 mode, with only weak parasitic features in the operating band. The structure is also tunable: the resonance frequency and coupling can be adjusted through geometric parameters while maintaining stable modal behavior, indicating good process tolerance. Finite-element analysis further suggests straightforward frequency scaling beyond 5 GHz by reducing the film and electrode thickness while preserving approximately 25% kt^2. In addition, introducing a SiO2 compensation layer is predicted to improve the temperature coefficient of frequency to approximately -25 ppm/deg C. These results establish complementary-polarity double-layer LiTaO3 as a practical platform for high-coupling, spurious-suppressed acoustic resonators and provide a scalable route toward wideband ultrasonic resonators, filters, and related transducers. △ Less

Submitted 27 April, 2026; originally announced April 2026.

Comments: 13 pages, 5 figures

Strongly Correlated Superconductivity in Twisted Bilayer Graphene: a Gutzwiller Study

Authors: Matthew Shu Liang, Yi-Jie Wang, Geng-Dong Zhou, Zhi-Da Song, Xi Dai

Abstract: We study strongly correlated superconductivity in magic-angle twisted bilayer graphene (MATBG) using a variational Gutzwiller wavefunction $\ket{Ψ_G} = \prod_{\vb{R}} \hat{P}_{\vb{R}} \ket{Φ_0}$, where the Gutzwiller projector $\hat{P}_{\vb{R}}$ is allowed to break charge U(1) symmetry to accommodate superconducting (SC) order. The ground state energy is evaluated via the \textit{Gutzwiller Approx… ▽ More We study strongly correlated superconductivity in magic-angle twisted bilayer graphene (MATBG) using a variational Gutzwiller wavefunction $\ket{Ψ_G} = \prod_{\vb{R}} \hat{P}_{\vb{R}} \ket{Φ_0}$, where the Gutzwiller projector $\hat{P}_{\vb{R}}$ is allowed to break charge U(1) symmetry to accommodate superconducting (SC) order. The ground state energy is evaluated via the \textit{Gutzwiller Approximation} applied to an 8-band model consisting of correlated $f$-orbitals and uncorrelated $c$-orbitals, with interactions including onsite Coulomb repulsion $U$, phonon-mediated anti-Hund's coupling $\hat{H}_{J_A}$, and intra-orbital Hund's coupling $\hat{H}_{J_H}$. At filling $ν= 2.5$, we map out the phase diagram as a function of $U$ and $J_A$, and reveal a strongly correlated SC (SC-SC) phase dominates at large $U$, wherethe strong on-site interaction U strongly suppress the $f$-orbital charge fluctuations while maintaining finite pairing order and a sizeable quasiparticle weight Z, distinguishing it from a conventional Mott insulator. For a range of $J_{\rm A}$, SC-SC transitions to FL as $U$ decreases, until the weakly correlated BCS-like SC (BCS-SC) re-enters as $U \to 0$. We further identify a novel small Fermi liquid (sFL) state with effective Fermi surface formed by $c$-orbitals, which is essentially different with the normal Fermi liquid. Interestingly, in the intermediate- ($U \lesssim 40$ meV) and large-$U$ ($U \gtrsim 40$ meV) regimes, the conventional FL and the sFL are the lowest-energy normal phases, respectively, potentially serve as the parent states of the SC-SC phase. These results illuminate the interplay between strong correlations and unconventional pairing in MATBG, and establish a versatile Gutzwiller framework applicable to other strongly correlated superconductors. △ Less

Submitted 15 June, 2026; v1 submitted 6 April, 2026; originally announced April 2026.

Annihilation of Dirac points and its topological obstruction in a photonic Kagome lattice

Authors: Zhaoyang Zhang, Matthieu Finck, Changchang Li, Shun Liang, Jerome Dubois, Yumin Tian, Jiahao Wen, Yanpeng Zhang, Guillaume Malpuech, Dmitry Solnyshkov

Abstract: Dirac points (DPs) are topological singularities that determine the extraordinary properties of two-dimensional materials. They are generally classified by discrete topological invariants, which determine the possibility of DPs' annihilation upon their collision. Here, we study the behaviors of DPs within a photonic Kagome lattice created in atomic vapor. With optically engineering the potential d… ▽ More Dirac points (DPs) are topological singularities that determine the extraordinary properties of two-dimensional materials. They are generally classified by discrete topological invariants, which determine the possibility of DPs' annihilation upon their collision. Here, we study the behaviors of DPs within a photonic Kagome lattice created in atomic vapor. With optically engineering the potential difference among three sites constituting the Kagome unit cell while preserving time-reversal symmetry and the stability of an isolated DP, the DPs move in reciprocal space. By employing conical diffraction to measure their position and the topological invariant (Euler number), we demonstrate an obstruction to DPs' annihilation during collision and a transition to a case where the Euler number changes and annihilation occurs. Such topological transition is induced by a non-Abelian frame rotation of the eigenstates around the Brillouin zone torus. The associated conversion of the DP quaternionic charges during their motion explains the change of Euler number. △ Less

Submitted 12 March, 2026; originally announced March 2026.

From stacking to function: emergent states and quantum devices in 2D superconductor heterostructures

Authors: Sichun Zhao, Junlin Xiong, Ji Zhou, Shi-Jun Liang, Bin Cheng, Feng Miao

Abstract: Two-dimensional (2D) superconductors provide a powerful building block for engineering emergent quantum states shaped by reduced dimensionality, enhanced quantum fluctuations, and interfacial symmetry breaking. In van der Waals heterostructures, atomically sharp and lattice-mismatch-free interfaces enable superconductivity to be deliberately coupled with magnetism, spin orbit interaction, and band… ▽ More Two-dimensional (2D) superconductors provide a powerful building block for engineering emergent quantum states shaped by reduced dimensionality, enhanced quantum fluctuations, and interfacial symmetry breaking. In van der Waals heterostructures, atomically sharp and lattice-mismatch-free interfaces enable superconductivity to be deliberately coupled with magnetism, spin orbit interaction, and band topology, allowing collective electronic orders to be combined and reconfigured in ways unattainable in bulk materials. This Review summarizes recent advances in vdW heterostructures of 2D superconductors, focusing on superconductor/magnet, superconductor/topological material, and superconductor/superconductor junctions. We discuss the microscopic mechanisms underlying proximity effects and highlight how interfacial exchange fields, spin orbit coupling, and twist-controlled tunneling give rise to unconventional pairing, long-range spin-triplet supercurrents, nonreciprocal Josephson transport, and topological superconductivity potentially hosting Majorana bound states. Beyond their fundamental significance, the ability to controllably generate topological and nonreciprocal superconducting states positions 2D superconductor heterostructures as promising building blocks for emerging quantum technologies, including ultra-sensitive quantum sensing, programmable superconducting logic, and energy-efficient quantum and neuromorphic computing architectures. Looking forward, advances in materials synthesis, interface engineering, and device integration are expected to further expand the scope and functionality of 2D superconductor heterostructures, reinforcing their role as a central platform for exploring and controlling emergent quantum phases. △ Less

Submitted 3 March, 2026; originally announced March 2026.

Journal ref: Invited review by Chinese Physics B (2026)

Non-equilibrium symmetry of cyclic first-passage times

Authors: Daniel Maria Busiello, Shiling Liang, Simone Pigolotti

Abstract: We study the sum of first passage times along an arbitrary cycle made up of N>2 states of a small physical system. We show that, if the system is at thermodynamic equilibrium, this sum follows the same probability distribution regardless of whether the cycle is explored clockwise or counterclockwise. Out of equilibrium, the distributions of clockwise and counterclockwise cyclic first passage times… ▽ More We study the sum of first passage times along an arbitrary cycle made up of N>2 states of a small physical system. We show that, if the system is at thermodynamic equilibrium, this sum follows the same probability distribution regardless of whether the cycle is explored clockwise or counterclockwise. Out of equilibrium, the distributions of clockwise and counterclockwise cyclic first passage times are related by a detailed fluctuation theorem. This result descends from a symmetry of clockwise and counterclockwise trajectories, which combines time reversal with swapping portions of the trajectories. We then relate the entropy produced along the cycle with the entropy production of the whole system using large deviation theory. Our results reveal a novel symmetry in stochastic systems, of potential broad applicability in non-equilibrium physics. △ Less

Submitted 25 January, 2026; originally announced January 2026.

Controlled Switching of Bose-Einstein Condensation in a Mixture of Two Species of Polaritons

Authors: Hassan Alnatah, Shuang Liang, Qiaochu Wan, Jonathan Beaumariage, Kirk Baldwin, Adbhut Gupta, Loren N. Pfeiffer, David W. Snoke

Abstract: We report temperature-dependent switching between lower and upper polariton condensation in a GaAs/AlGaAs microcavity when both of these species have comparable populations in a mixture. Using angle-resolved photoluminescence, we observe that at low temperatures, condensation occurs in the lower polariton branch, while at elevated temperatures, the upper polariton branch can become favored. At an… ▽ More We report temperature-dependent switching between lower and upper polariton condensation in a GaAs/AlGaAs microcavity when both of these species have comparable populations in a mixture. Using angle-resolved photoluminescence, we observe that at low temperatures, condensation occurs in the lower polariton branch, while at elevated temperatures, the upper polariton branch can become favored. At an intermediate temperature, we observe instability in the condensate formation, characterized by metastable correlations of the fluctuations in intensity and linewidth of the lower and upper polariton branches. △ Less

Submitted 10 June, 2026; v1 submitted 22 January, 2026; originally announced January 2026.

Interlayer Coupling Driven Correlated and Charge-Ordered Electronic States in a Transition Metal Dichalcogenide Superlattice

Authors: Yiwei Li, Lixuan Xu, Shihao Zhang, Lanxin Liu, Yifan Zhou, Qiang Wan, Shiwei Chen, Shiheng Liang, Yulin Chen, Yi-feng Yang, Xuan Luo, Yuping Sun, Nan Xu, Zhongkai Liu

Abstract: 4Hb-TaS_2, a van der Waals superlattice comprising alternate stacked Ising superconducting 1H-TaS_2 and cluster Mott insulating 1T-TaS_2, exhibits emergent properties beyond those of its constituent layers. Notable phenomena include time-reversal-symmetry-breaking superconductivity and spontaneous vortex phases, which are driven by nontrivial interlayer interactions that remain debated. Using area… ▽ More 4Hb-TaS_2, a van der Waals superlattice comprising alternate stacked Ising superconducting 1H-TaS_2 and cluster Mott insulating 1T-TaS_2, exhibits emergent properties beyond those of its constituent layers. Notable phenomena include time-reversal-symmetry-breaking superconductivity and spontaneous vortex phases, which are driven by nontrivial interlayer interactions that remain debated. Using area-selective angle-resolved photoemission spectroscopy, we provide direct spectroscopic evidence of such interaction by systematically probing the electronic structures of 1T- and 1H-terminted surfaces of 4Hb-TaS_2. The metallic states of subsurface 1H-layers are folded to the Brillouin zone center by the sqrt(13) by sqrt(13) modulation of the surface 1T-layer, forming chiral "windmill" Fermi surfaces via Umklapp scattering. These conducting states further hybridize with the incipient flat band of the surface 1T-layer, producing a Kondo-like peak at the Fermi level. Interlayer charge transfer induces distinct 3 by 3 and 2 by 2 charge orders on the surface and subsurface 1H-layers, respectively, which result in characteristic segmented Fermi surfaces and dichotomously shift the van Hove singularities. These findings reconcile the competing Kondo and Mott-Hubbard models in this material and emphasize the interplay of flat bands, van hove singularities, charge orders, and unconventional superconductivity in correlated superlattices. △ Less

Submitted 27 May, 2026; v1 submitted 18 November, 2025; originally announced November 2025.

Comments: accepted in Newton

All-Electrical Self-Switching of van der Waals Chiral Antiferromagnet

Authors: Junlin Xiong, Jiawei Jiang, Yanwei Cui, Han Gao, Ji Zhou, Zijia Liu, KuiKui Zhang, Shaobo Cheng, Kehui Wu, Sang-Wook Cheong, Kai Chang, Zhongkai Liu, Hongxin Yang, Shi-Jun Liang, Bin Cheng, Feng Miao

Abstract: Antiferromagnets have garnered significant attention due to their negligible stray field and ultrafast magnetic dynamics, which are promising for high-density and ultrafast spintronic applications. Their dual functionality as both spin sources and information carriers could enable all-electrical self-induced switching of antiferromagnetic order, offering great potential for ultra-compact spintroni… ▽ More Antiferromagnets have garnered significant attention due to their negligible stray field and ultrafast magnetic dynamics, which are promising for high-density and ultrafast spintronic applications. Their dual functionality as both spin sources and information carriers could enable all-electrical self-induced switching of antiferromagnetic order, offering great potential for ultra-compact spintronic devices. However, related progress is still elusive. Here, we report the deterministic switching of chiral antiferromagnetic orders induced by charge current at zero external magnetic field in the van der Waals (vdW) magnetically intercalated transition metal dichalcogenide CoTa3S6. This system exhibits strong interactions between cobalt atom magnetic moment lattice and itinerant electrons within the metallic layers, as demonstrated by temperature-dependent angle-resolved photoemission, scanning tunneling spectroscopy, and topological Nernst effect measurements. Notably, the itinerant-localization interactions lead to current-induced chiral spin orbit torques as well as Ruderman-Kittel-Kasuya-Yosida (RKKY) exchange torques that interact with the localized magnetic moments, facilitating all-electrical switching of the chiral magnetic order in the CoTa3S6 flake. Our work opens a promising avenue for manipulating antiferromagnetic orders by delicately engineering the synergistic interactions between magnetic moments and itinerant electrons. △ Less

Submitted 20 October, 2025; originally announced October 2025.

Topological Robustness of Anyon Tunneling at $ν= 1/3$

Authors: Adithya Suresh, Ramon Guerrero-Suarez, Tanmay Maiti, Shuang Liang, Geoffrey Gardner, Claudio Chamon, Michael Manfra

Abstract: The scaling exponent $g$ of the quasiparticle propagator for incompressible fractional quantum Hall states in the Laughlin sequence is expected to be robust against perturbations that do not close the gap. Here we probe the topological robustness of the chiral Luttinger liquid at the boundary of the $ν=1/3$ state by measuring the tunneling conductance between counterpropagating edge modes as a fun… ▽ More The scaling exponent $g$ of the quasiparticle propagator for incompressible fractional quantum Hall states in the Laughlin sequence is expected to be robust against perturbations that do not close the gap. Here we probe the topological robustness of the chiral Luttinger liquid at the boundary of the $ν=1/3$ state by measuring the tunneling conductance between counterpropagating edge modes as a function of quantum point contact transmission. We demonstrate that for transmission $t\geq 0.7$ the tunneling conductance is well-described by the first two terms of a perturbative series expansion corresponding to $g=1/3$. We further demonstrate that the measured scaling exponent is robustly pinned to $g=1/3$ across the plateau, only deviating as the bulk state becomes compressible. Finally we examine the impact of weak disorder on the scaling exponent, finding it insensitive. These measurements firmly establish the topological robustness of anyon tunneling at $ν=1/3$ and substantiate the chiral Luttinger liquid description of the edge mode. △ Less

Submitted 13 October, 2025; originally announced October 2025.

Comments: 6+5 pages, 4+2 figures

Quantum Transport Reservoir Computing

Authors: Yecheng Jing, Pengfei Wang, Shuai Zhang, Zhoujie Zeng, Shi-Jun Liang, Wei Chen

Abstract: Reservoir computing (RC), a neural network designed for temporal data, enables efficient computation with low-cost training and direct physical implementation. Recently, quantum RC has opened new possibilities for conventional RC and introduced novel ideas to tackle open problems in quantum physics and advance quantum technologies. Despite its promise, it faces challenges, including physical reali… ▽ More Reservoir computing (RC), a neural network designed for temporal data, enables efficient computation with low-cost training and direct physical implementation. Recently, quantum RC has opened new possibilities for conventional RC and introduced novel ideas to tackle open problems in quantum physics and advance quantum technologies. Despite its promise, it faces challenges, including physical realization, output readout, and measurement-induced back-action. Here, we propose to implement quantum RC through quantum transport in mesoscopic electronic systems. Our approach possesses several advantages: compatibility with existing device fabrication techniques, ease of output measurement, and robustness against measurement back-action. Leveraging universal conductance fluctuations, we numerically demonstrate two benchmark tasks, spoken-digit recognition and time-series forecasting, to validate our proposal. This work establishes a novel pathway for implementing on-chip quantum RC via quantum transport and expands the mesoscopic physics applications. △ Less

Submitted 4 November, 2025; v1 submitted 9 September, 2025; originally announced September 2025.

Comments: 10 pages, 8 figures

Journal ref: Phys. Rev. Applied 24, 044036 (2025)

Cavity-Mediated Coupling between Local and Nonlocal Modes in Landau Polaritons

Authors: Sae R. Endo, Dasom Kim, Shuang Liang, Geon Lee, Sunghwan Kim, Alan Covarrubias-Morales, Minah Seo, Michael J. Manfra, Dukhyung Lee, Motoaki Bamba, Junichiro Kono

Abstract: The multimode ultrastrong coupling (USC) regime has emerged as a novel platform for accessing previously inaccessible phenomena in cavity quantum electrodynamics. Of particular interest are cavity-mediated correlations between local and nonlocal excitations, or equivalently, between modes at zero and finite in-plane momentum modes, which offer new opportunities for controlling light-matter interac… ▽ More The multimode ultrastrong coupling (USC) regime has emerged as a novel platform for accessing previously inaccessible phenomena in cavity quantum electrodynamics. Of particular interest are cavity-mediated correlations between local and nonlocal excitations, or equivalently, between modes at zero and finite in-plane momentum modes, which offer new opportunities for controlling light-matter interactions across space. However, direct experimental evidence of such interactions has remained elusive. Here, we demonstrate nonlocal multimode coupling in a Landau polariton system, where cavity photons simultaneously interact with the zero-momentum cyclotron resonance and finite-momentum magnetoplasmons of a two-dimensional electron gas in a GaAs quantum well. Our slot cavities, with their subwavelength mode volumes, supply in-plane momentum components that enable the excitation of finite-momentum matter modes. Terahertz time-domain magnetospectroscopy measurements reveal a clear splitting of the upper-polariton branch, arising from hybridization between magnetoplasmon modes and the cavity--cyclotron-resonance hybrids. Extracted coupling strengths confirm USC of the cyclotron resonance and strong coupling of the magnetoplasmon modes to the cavity field, respectively. The experimental results are well captured by the multimode Hopfield model and finite-element simulations. These findings establish a pathway for engineering multimode light-matter interactions involving zero- and finite-momentum matter modes in the USC regime. △ Less

Submitted 6 September, 2025; originally announced September 2025.

Distinct Lifetimes for $X$ and $Z$ Loop Measurements in a Majorana Tetron Device

Authors: Morteza Aghaee, Zulfi Alam, Rikke Andersen, Mariusz Andrzejczuk, Andrey Antipov, Mikhail Astafev, Lukas Avilovas, Ahmad Azizimanesh, Eric Banek, Bela Bauer, Jonathan Becker, Umesh Kumar Bhaskar, Andrea G. Boa, Srini Boddapati, Nichlaus Bohac, Jouri D. S. Bommer, Jan Borovsky, Léo Bourdet, Samuel Boutin, Lucas Casparis, Srivatsa Chakravarthi, Hamidreza Chalabi, Benjamin J. Chapman, Nikolaos Chatzaras, Tzu-Chiao Chien , et al. (142 additional authors not shown)

Abstract: We present a hardware realization and measurements of a tetron qubit device in a superconductor-semiconductor heterostructure. The device architecture contains two parallel superconducting nanowires, which support four Majorana zero modes (MZMs) when tuned into the topological phase, and a trivial superconducting backbone. Two distinct readout interferometers are formed by connecting the supercond… ▽ More We present a hardware realization and measurements of a tetron qubit device in a superconductor-semiconductor heterostructure. The device architecture contains two parallel superconducting nanowires, which support four Majorana zero modes (MZMs) when tuned into the topological phase, and a trivial superconducting backbone. Two distinct readout interferometers are formed by connecting the superconducting structure to a series of quantum dots. We perform single-shot interferometric measurements of the fermion parity for the two loops, designed to implement Pauli-$X$ and $Z$ measurements of the tetron. Performing repeated single-shot measurements yields two widely separated time scales $τ_X = 14.5\pm 0.3 \, \mathrm{μs}$ and $τ_Z = 12.4\pm 0.4\, \mathrm{ms}$ for parity switches observed in the $X$ and $Z$ measurement loops, which we attribute to intra-wire parity switches and external quasiparticle poisoning, respectively. We estimate assignment errors of $\mathrm{err}^X_a=16\%$ and $\mathrm{err}^Z_a=0.5\%$ for $X$ and $Z$ measurement-based operations, respectively. △ Less

Submitted 4 September, 2025; v1 submitted 11 July, 2025; originally announced July 2025.

Comments: Extended discussion of switching dynamics and multiple time scales in App. A. Added App. C on alternative scenarios. Corrected Figs. 2(i) & A4. Explained the method for extracting multiple time scales from long time traces in App. A

Mirror-mediated long-range coupling and robust phase locking of spatially separated exciton-polariton condensates

Authors: Shuang Liang, Hassan Alnatah, Qi Yao, Jonathan Beaumariage, Ken West, Kirk Baldwin, Adbhut Gupta, Loren N. Pfeiffer, Natalia G. Berloff, David W. Snoke

Abstract: Lattice arrays are valuable simulators for complex mathematical problems, but physical systems typically allow only short-range coupling. We demonstrate a method for independently tunable, long-range interactions between polariton condensates in two-dimensional lattices by using vertical emission and external imaging to couple arbitrary sites. Two geometrically isolated condensates are phase-locke… ▽ More Lattice arrays are valuable simulators for complex mathematical problems, but physical systems typically allow only short-range coupling. We demonstrate a method for independently tunable, long-range interactions between polariton condensates in two-dimensional lattices by using vertical emission and external imaging to couple arbitrary sites. Two geometrically isolated condensates are phase-locked without planar coupling, verified via phase-resolved interferometry. Analytical modeling reveals mechanisms for robust coherence. The mirror-based scheme, free of cameras or modulators, offers a pure, high-bandwidth analogt element. Extension to dense graphs via segmented micro-mirrors is limited only by imaging optics, enabling scalable, energy-efficient polaritonic hardware for neuromorphic computation. △ Less

Submitted 1 July, 2026; v1 submitted 25 June, 2025; originally announced June 2025.

Collision-assisted information scrambling on a configurable photonic chip

Authors: Xiao-Wen Shang, Shu-Yi Liang, Guan-Ju Yan, Xin-Yang Jiang, Zi-Ming Yin, Hao Tang, Jian-Peng Dou, Ze-Kun Jiang, Yu-Quan Peng, Xian-Min Jin

Abstract: Quantum interference and entanglement are in the core of quantum computations. The fast spread of information in the quantum circuit helps to mitigate the circuit depth. Although the information scrambling in the closed systems has been proposed and tested in the digital circuits, how to measure the evolution of quantum correlations between systems and environments remains a delicate and open ques… ▽ More Quantum interference and entanglement are in the core of quantum computations. The fast spread of information in the quantum circuit helps to mitigate the circuit depth. Although the information scrambling in the closed systems has been proposed and tested in the digital circuits, how to measure the evolution of quantum correlations between systems and environments remains a delicate and open question. Here, we propose a photonic circuit to investigate the information scrambling in an open quantum system by implementing the collision model with cascaded Mach-Zehnder interferometers. We numerically simulate the photon propagation and find that the tripartite mutual information strongly depends on the system-environment and environment-environment interactions. We further reduce the number of observables and the number of shots required to reconstruct the density matrix by designing an enhanced compressed sensing. Our results provide a reconfigurable photonic platform for simulating open quantum systems and pave the way for exploring controllable dissipation and non-Markovianity in discrete-variable photonic computing. △ Less

Submitted 19 June, 2025; originally announced June 2025.

Comments: 7 pages, 4 figures. Comments are welcome!

Dimensionality-Driven Anomalous Metallic State with Zero-field Nonreciprocal Transport in Layered Ising Superconductors

Authors: Yanwei Cui, Zenglin Liu, Qin Liu, Junlin Xiong, Yongqin Xie, Yudi Dai, Ji Zhou, Lizheng Wang, Hanyan Fang, Haiwen Liu, Shi-Jun Liang, Bin Cheng, Feng Miao

Abstract: The anomalous metal state (AMS), observed in failed superconductors, provides insights into superconductivity and quantum criticality, with studies revealing unconventional quantum phases like the Bose metal. Recently, layered transition metal dichalcogenide (TMD) superconductors approaching the two-dimensional limit have garnered significant attention for the enhanced phase fluctuations and elect… ▽ More The anomalous metal state (AMS), observed in failed superconductors, provides insights into superconductivity and quantum criticality, with studies revealing unconventional quantum phases like the Bose metal. Recently, layered transition metal dichalcogenide (TMD) superconductors approaching the two-dimensional limit have garnered significant attention for the enhanced phase fluctuations and electronic correlations. Investigating AMS in these systems, particularly in the absence of an external magnetic field, could offer valuable insights into the dimensionality-driven emergence of exotic quantum phenomena, including triplet Cooper pairing, phase fluctuation dynamics, and especially the recently discovered field-free superconducting diode effects. However, the field-free AMS has yet to be observed in TMD superconductors. Here, we report the dimensionality-tunable AMS near the superconducting quantum phase transitions in a layered TMD superconductor 2H-Ta2S3Se. In samples with thicknesses below 10 nm, we demonstrate magnetic field-driven AMS under external magnetic field, characterized by the vanishing of the Hall resistance and the presence of finite longitudinal resistance. Remarkably, an unexpected zero-field AMS emerges as the sample thickness is reduced to 3 nm. This AMS aligns well with the quantum vortex creep model and exhibits non-reciprocal transport behaviors, suggesting the onset of spontaneous time-reversal symmetry breaking accompanied by vortex motion as the system approaches the two-dimensional limit. Our findings open new avenues for exploring dimensionality-driven exotic superconducting quantum critical phases, and pave the way for a deeper understanding of zero-field superconducting diode effects. △ Less

Submitted 28 May, 2025; originally announced May 2025.

Demonstration of returning Thouless pump in a Berry dipole system

Authors: Qingyang Mo, Shanjun Liang, Xiangke Lan, Jie Zhu, Shuang Zhang

Abstract: The Thouless pump, a cornerstone of topological physics, enables unidirectional quantized wave/particle transport via geometric Berry phase engineering in periodically driven systems. While decades of research have been dedicated to monopole-mediated pumping, mechanisms governed by higher-order singularities like Berry dipoles remain unexplored. Here, we report the experimental demonstration of a… ▽ More The Thouless pump, a cornerstone of topological physics, enables unidirectional quantized wave/particle transport via geometric Berry phase engineering in periodically driven systems. While decades of research have been dedicated to monopole-mediated pumping, mechanisms governed by higher-order singularities like Berry dipoles remain unexplored. Here, we report the experimental demonstration of a Berry-dipole-mediated returning Thouless pump (RTP) in a 1D acoustic waveguide array achieved through adiabatic encircling of a Berry dipole singularity. During this adiabatic cycle, an initial edge-localized mode first delocalizes into the bulk and eventually returns to the original edge, marking the characteristic signature of the RTP. Notably, this RTP exhibits an interesting feature of pseudospin flipping. The demonstrated RTP contrasts sharply with the well-studied monopole-governed pumps that feature unidirectional transport. △ Less

Submitted 16 October, 2025; v1 submitted 13 May, 2025; originally announced May 2025.

Tensor-monopole-induced topological boundary effects in four-dimensional acoustic metamaterials

Authors: Qingyang Mo, Shanjun Liang, Cuicui Lu, Jie Zhu, Shuang Zhang

Abstract: Gauge field theory provides the mathematical and conceptual framework to describe and understand topological singularities such as Weyl points and magnetic monopoles. While singularities associated with vector electromagnetic gauge fields have been well-studied, those of higher-form tensor gauge fields, like the four-dimensional (4D) tensor monopoles predicted by string theory, have remained large… ▽ More Gauge field theory provides the mathematical and conceptual framework to describe and understand topological singularities such as Weyl points and magnetic monopoles. While singularities associated with vector electromagnetic gauge fields have been well-studied, those of higher-form tensor gauge fields, like the four-dimensional (4D) tensor monopoles predicted by string theory, have remained largely theoretical or limited to experimental demonstration in pure synthetic dimensions, thereby not allowing investigations of the associated boundary effects. Here, we present a 4D system with tensor monopoles using engineered acoustic metamaterials. Our momentum space combines three real momentum dimensions and a geometric parameter as the fourth. By varying this fourth momentum, we experimentally reveal two distinct topological surface states in 3D subsystems: Fermi-arc surface states in a gapless subsystem and Dirac-cone surface states in a gapped subsystem. Our work introduces a novel platform for exploring new topological structures associated with tensor gauge field and topological phenomena in higher dimensions. △ Less

Submitted 17 April, 2025; originally announced April 2025.

Universal Anyon Tunneling in a Chiral Luttinger Liquid

Authors: Ramon Guerrero-Suarez, Adithya Suresh, Tanmay Maiti, Shuang Liang, James Nakamura, Geoffrey Gardner, Claudio Chamon, Michael Manfra

Abstract: The edge modes of fractional quantum Hall liquids are described by chiral Luttinger liquid theory. Despite many years of experimental investigation fractional quantum Hall edge modes remain enigmatic with significant discrepancies between experimental observations and detailed predictions of chiral Luttinger liquid theory. Here we report measurements of tunneling conductance between counterpropaga… ▽ More The edge modes of fractional quantum Hall liquids are described by chiral Luttinger liquid theory. Despite many years of experimental investigation fractional quantum Hall edge modes remain enigmatic with significant discrepancies between experimental observations and detailed predictions of chiral Luttinger liquid theory. Here we report measurements of tunneling conductance between counterpropagating edge modes at $ν=1/3$ across a quantum point contact fabricated on an AlGaAs/GaAs heterostructure designed to promote a sharp confinement potential. We present evidence for tunneling of anyons through a $ν=1/3$ incompressible liquid that exhibits universal scaling behavior with respect to temperature, source-drain bias, and barrier transmission, as originally proposed by Wen [1, 2]. For transmission $t\geq0.800$, we measured the tunneling exponent $\bar{g} = 0.333 \pm 0.005$ averaged over 29 independent data sets, consistent with the scaling dimension $Δ= g/2 = 1/6$ for a Laughlin quasiparticle at the edge. When combined with measurements of the fractional charge $e^*=e/3$ and the recently observed anyonic statistical angle $θ_a=\frac{2π}{3}$, the measured tunneling exponent fully characterizes the topological order of the primary Laughlin state at $ν=1/3$. △ Less

Submitted 15 June, 2025; v1 submitted 27 February, 2025; originally announced February 2025.

Comments: 10 pages, 4 figures

High-Velocity Magnetic Domain Wall Motion Driven by Acoustic Spin Transfer Torque

Authors: Jiacheng Lu, Fa Chen, Yiming Shu, Yukang Wen, Hang Zou, Yuhao Liu, Shiheng Liang, Wei Luo, Yue Zhang

Abstract: We predict high-velocity magnetic domain wall (DW) motion driven by out-of-plane acoustic spin in surface acoustic waves (SAWs). We demonstrate that the SAW propagating at a 30-degree angle relative to the x-axis of a 128-degree Y-LiNbO3 substrate exhibits uniform out-of-plane spin angular momentum. This acoustic spin triggers the DW motion at a velocity exceeding 50 m/s in a way that is similar t… ▽ More We predict high-velocity magnetic domain wall (DW) motion driven by out-of-plane acoustic spin in surface acoustic waves (SAWs). We demonstrate that the SAW propagating at a 30-degree angle relative to the x-axis of a 128-degree Y-LiNbO3 substrate exhibits uniform out-of-plane spin angular momentum. This acoustic spin triggers the DW motion at a velocity exceeding 50 m/s in a way that is similar to the spin-transfer-torque (STT) effect. This phenomenon highlights the potential of acoustic spin in enabling rapid DW displacement, offering an innovative approach to developing energy-efficient spintronic devices. △ Less

Submitted 14 April, 2025; v1 submitted 25 February, 2025; originally announced February 2025.

Deployable Nanoelectromechanical Bound States in the Continuum Enabled by GHz Lamb Wave Phononic Crystals on LiNbO3 Thin Films

Authors: Sheng-Nan Liang, Zhen-Hui Qin, Shu-Mao Wu, Hua-Yang Chen, Si-Yuan Yu, Yan-Feng Chen

Abstract: Bound states in the continuum (BICs) are a fascinating class of eigenstates that trap energy within the continuum, enabling breakthroughs in ultra-low-threshold lasing, high-Q sensing, and advanced wave-matter interactions. However, their stringent symmetry requirements hinder practical integration, especially in acoustic and electromechanical systems where efficient mode excitation is challenging… ▽ More Bound states in the continuum (BICs) are a fascinating class of eigenstates that trap energy within the continuum, enabling breakthroughs in ultra-low-threshold lasing, high-Q sensing, and advanced wave-matter interactions. However, their stringent symmetry requirements hinder practical integration, especially in acoustic and electromechanical systems where efficient mode excitation is challenging. Here, we demonstrate deployable nanoelectromechanical quasi-BICs on suspended lithium niobate (LiNbO3) thin films, enabled by nanoscale Lamb wave phononic crystals (PnCs) operating at gigahertz frequencies. By exploiting the decoupling of symmetric (S) and antisymmetric (A) Lamb wave modes, we create a robust framework for BICs. Controlled mirror symmetry breaking induces targeted coupling between the S and A modes, resulting in quasi-BICs that preserve high-Q characteristics and can be excited by traveling waves, eliminating the need for specialized excitation schemes. Our approach enables the multiplexing of quasi-BIC resonators along a single transmission line, each corresponding to a unique frequency and spatial position. This work presents a scalable route for the on-chip integration of BICs, bridging the gap between theoretical concepts and practical nanoelectromechanical devices, and opening new avenues in advanced signal processing, high-precision sensing, and quantum acoustics. △ Less

Submitted 25 February, 2025; originally announced February 2025.

Journal ref: Physical Review Letters 135, 206201 (2025)

Strong coupling of polaritons at room temperature in a GaAs/AlGaAs structure

Authors: Hassan Alnatah, Shuang Liang, Qiaochu Wan, Jonathan Beaumariage, Ken West, Kirk Baldwin, Loren N. Pfeiffer, Man Chun Alan Tam, Zbigniew R. Wasilewski, David W. Snoke

Abstract: We report direct measurement of the dispersion relation of polaritons in GaAs/AlGaAs microcavity structures at room temperature, which clearly shows that the polaritons are in the strong coupling limit. The Rabi splitting of the polariton states decreases as the polariton gas increases in density, but even when the polariton gas becomes a coherent, Bose-condensate-like state, the polaritons retain… ▽ More We report direct measurement of the dispersion relation of polaritons in GaAs/AlGaAs microcavity structures at room temperature, which clearly shows that the polaritons are in the strong coupling limit. The Rabi splitting of the polariton states decreases as the polariton gas increases in density, but even when the polariton gas becomes a coherent, Bose-condensate-like state, the polaritons retain a strong exciton component, as seen in the nonlinear energy shift of the light emission. This opens up the possibility of polaritonic devices at room temperature in a material system which can be grown with very high quality and uniformity. △ Less

Submitted 6 April, 2025; v1 submitted 17 February, 2025; originally announced February 2025.

Transformer-Enhanced Variational Autoencoder for Crystal Structure Prediction

Authors: Ziyi Chen, Yang Yuan, Siming Zheng, Jialong Guo, Sihan Liang, Yangang Wang, Zongguo Wang

Abstract: Crystal structure forms the foundation for understanding the physical and chemical properties of materials. Generative models have emerged as a new paradigm in crystal structure prediction(CSP), however, accurately capturing key characteristics of crystal structures, such as periodicity and symmetry, remains a significant challenge. In this paper, we propose a Transformer-Enhanced Variational Auto… ▽ More Crystal structure forms the foundation for understanding the physical and chemical properties of materials. Generative models have emerged as a new paradigm in crystal structure prediction(CSP), however, accurately capturing key characteristics of crystal structures, such as periodicity and symmetry, remains a significant challenge. In this paper, we propose a Transformer-Enhanced Variational Autoencoder for Crystal Structure Prediction (TransVAE-CSP), who learns the characteristic distribution space of stable materials, enabling both the reconstruction and generation of crystal structures. TransVAE-CSP integrates adaptive distance expansion with irreducible representation to effectively capture the periodicity and symmetry of crystal structures, and the encoder is a transformer network based on an equivariant dot product attention mechanism. Experimental results on the carbon_24, perov_5, and mp_20 datasets demonstrate that TransVAE-CSP outperforms existing methods in structure reconstruction and generation tasks under various modeling metrics, offering a powerful tool for crystal structure design and optimization. △ Less

Submitted 13 February, 2025; originally announced February 2025.

Discovery of a large magnetic nonlinear Hall effect in an altermagnet

Authors: Lei Han, Xizhi Fu, Cheng Song, Yuxiang Zhu, Xiaokang Li, Zengwei Zhu, Hua Bai, Ruiyue Chu, Jiankun Dai, Shixuan Liang, Maciej Sawicki, Junwei Liu, Feng Pan

Abstract: Since Edwin Halls groundbreaking discovery of the Hall effect in 1879, magnetism, spin, and quantization have been expanding the scope of Hall effects, continuously driving transformative progress in science and technology. Among them, the latest nonlinear Hall effect (NLHE), where longitudinal electric field tunes quantum geometry to generate nonlinear Hall voltage, attracts wide attention as a s… ▽ More Since Edwin Halls groundbreaking discovery of the Hall effect in 1879, magnetism, spin, and quantization have been expanding the scope of Hall effects, continuously driving transformative progress in science and technology. Among them, the latest nonlinear Hall effect (NLHE), where longitudinal electric field tunes quantum geometry to generate nonlinear Hall voltage, attracts wide attention as a sensitive probe of topological phases across a wide range of materials. Here, we report a new Hall effect member: the magnetic nonlinear Hall effect (MNLHE), characterized by a quadratic Hall conductivity dependence on magnetic field, rather than electric field as in NLHE. This finding relies on an altermagnet, Mn5Si3 thin film, whose alternating-sign Berry curvatures ensure higher-order MNLHE clearly distinguishable from the first-order anomalous Hall effect. The observed quadratic dependence originates from chiral next-nearest-neighbor hopping processes that acquire magnetic-exchange-driven Zeeman energies and Haldane-like chiral flux phases. Remarkably, this MNLHE is non-analytic, as reversing the magnetic field flips the alternating spin-splitting bands and reverses the hopping chirality, which is absent in traditional NLHE. Beyond offering a distinctive transport fingerprint for altermagnet Mn5Si3 thin film, this MNLHE is large and unsaturated up to 60 T, providing opportunities for pulsed high-field sensing technologies in both fundamental researches and engineering applications. △ Less

Submitted 14 March, 2025; v1 submitted 7 February, 2025; originally announced February 2025.

Comments: 29 pages, 4 figures

Single electron interference and capacitive edge mode coupling generates $Φ_0/2$ flux periodicity in Fabry-Perot interferometers

Authors: Shuang Liang, James Nakamura, Geoffrey C. Gardner, Michael J. Manfra

Abstract: Experimental observations of flux periodicity $φ_{0}/2$, where $φ_0=h/e$, for interference of the outermost edge mode in the integer quantum Hall regime have been attributed to an exotic electron pairing mechanism. We present measurements of an AlGaAs/GaAs Fabry-Perot interferometer operated in the integer quantum Hall regime for filling factors $1\leq ν\leq 3$ that has been designed to simultaneo… ▽ More Experimental observations of flux periodicity $φ_{0}/2$, where $φ_0=h/e$, for interference of the outermost edge mode in the integer quantum Hall regime have been attributed to an exotic electron pairing mechanism. We present measurements of an AlGaAs/GaAs Fabry-Perot interferometer operated in the integer quantum Hall regime for filling factors $1\leq ν\leq 3$ that has been designed to simultaneously express measurable bulk-edge and edge-edge couplings. At integer fillings $ν=2$ and $ν=3$, we observe interference with flux periodicity $φ_{0}/2$ for the outermost edge mode. Our analysis indicates that the periodicity $φ_0/2$ is not driven by electron pairing but is the result of capacitive coupling between isolated edge modes and the interfering outer edge. The interfering unit of charge for the outermost edge mode at $ν=2$ and $ν=3$ was determined to be $e^*=1$, where the effective charge $e^*$ is normalized to the charge of an electron. Our measurements demonstrate that the magnitude of the interfering charge can be determined in operando in a Fabry-Perot interferometer. △ Less

Submitted 23 June, 2025; v1 submitted 31 January, 2025; originally announced February 2025.

Comments: 16 pages, 4 figures

Skin-inspired in-sensor encoding of strain vector using tunable quantum geometry

Authors: Zenglin Liu, Jingwen Shi, Jin Cao, Zecheng Ma, Zaizheng Yang, Yanwei Cui, Lizheng Wang, Yudi Dai, Moyu Chen, Pengfei Wang, Yongqin Xie, Fanqiang Chen, Youguo Shi, Cong Xiao, Shengyuan A. Yang, Bin Cheng, Shi-Jun Liang, Feng Miao

Abstract: Human skin provides crucial tactile feedback, allowing us to skillfully perceive various objects by sensing and encoding complex deformations through multiple parameters in each tactile receptor. However, replicating this high-dimensional tactile perception with conventional materials' electronic properties remains a daunting challenge. Here, we present a skin-inspired method to encode strain vect… ▽ More Human skin provides crucial tactile feedback, allowing us to skillfully perceive various objects by sensing and encoding complex deformations through multiple parameters in each tactile receptor. However, replicating this high-dimensional tactile perception with conventional materials' electronic properties remains a daunting challenge. Here, we present a skin-inspired method to encode strain vectors directly within a sensor. This is achieved by leveraging the strain-tunable quantum properties of electronic bands in the van der Waals topological semimetal Td -WTe2. We observe robust and independent responses from the second-order and third-order nonlinear Hall signals in Td -WTe2 when subjected to variations in both the magnitude and direction of strain. Through rigorous temperature-dependent measurements and scaling law analysis, we establish that these strain responses primarily stem from quantum geometry-related phenomena, including the Berry curvature and Berry-connection polarizability tensor. Furthermore, our study demonstrates that the strain-dependent nonlinear Hall signals can efficiently encode high-dimensional strain information using a single device. This capability enables accurate and comprehensive sensing of complex strain patterns in the embossed character "NJU". Our findings highlight the promising application of topological quantum materials in advancing next-generation, bio-inspired flexible electronics. △ Less

Submitted 7 January, 2025; originally announced January 2025.

Comments: Published in Advanced Functional Materials (2024)

Observation of nonreciprocal transverse localization of light

Authors: Shun Liang, Changchang Li, Wenqing Yu, Zhenzhi Liu, Changbiao Li, Yanpeng Zhang, Guillaume Malpuech, Dmitry Solnyshkov, Hui Jing, Zhaoyang Zhang

Abstract: Magnetic-free nonreciprocal optical devices that can prevent backscattering of signals are essential for integrated optical information processing. The achieved nonreciprocal behaviors mostly rely on various dispersive effects in optical media, which give rise to dispersive modulations of the transverse beam profile, such as spatial broadening and discretization, of the incident signals. Such defo… ▽ More Magnetic-free nonreciprocal optical devices that can prevent backscattering of signals are essential for integrated optical information processing. The achieved nonreciprocal behaviors mostly rely on various dispersive effects in optical media, which give rise to dispersive modulations of the transverse beam profile, such as spatial broadening and discretization, of the incident signals. Such deformation inevitably reduces the matching with subsequent components for information processing. Here we experimentally demonstrate the nonreciprocal transverse localization of light in a moiré photonic lattice induced in atomic vapors. When the probe field is set to co- or counter-propagate with the coupling field formed by superposing two identical honeycomb beams in a certain rotation angle, the output pattern can exhibit localized or dispersive behavior. The localization in the forward case is derived from the moiré structure, and the nonreciprocal behaviors (in both beam size and transmitted intensity) are introduced by the thermal motion of atoms. The thermal-motion-induced Doppler effect can destroy the coherent condition for electromagnetically induced transparency in the backward case, because of which the probe beam becomes immune to the modulation of the coupling field. The current work provides an approach to control the transverse beam profile in one-way transmission. △ Less

Submitted 31 December, 2024; originally announced January 2025.

Nonlinear Response Identities and Bounds for Nonequilibrium Steady States

Authors: Ruicheng Bao, Shiling Liang

Abstract: Understanding how systems respond to external perturbations is fundamental to statistical physics. For systems far from equilibrium, a general framework for response remains elusive. While progress has been made on the linear response of nonequilibrium systems, a theory for the nonlinear regime under finite perturbations has been lacking. Here, building on a novel connection between response and m… ▽ More Understanding how systems respond to external perturbations is fundamental to statistical physics. For systems far from equilibrium, a general framework for response remains elusive. While progress has been made on the linear response of nonequilibrium systems, a theory for the nonlinear regime under finite perturbations has been lacking. Here, building on a novel connection between response and mean first-passage times in continuous-time Markov chains, we derive a comprehensive theory for the nonlinear response to archetypal local perturbations. We establish an exact identity that universally connects the nonlinear response of any observable to its linear counterpart via a simple scaling factor. This identity directly yields universal bounds on the response magnitude. Furthermore, we establish a universal bound on response resolution -- an inequality constraining an observable's change by its intrinsic fluctuations -- thereby setting a fundamental limit on signal-to-noise ratio. These results provide a rigorous and general framework for analyzing nonlinear response far from equilibrium, which we illustrate with an application to transcriptional regulation. △ Less

Submitted 2 March, 2026; v1 submitted 27 December, 2024; originally announced December 2024.

Probing the Néel order in altermagnetic RuO2 films by X-ray magnetic linear dichroism

Authors: Yi-Chi Zhang, Hua Bai, Chong Chen, Lei Han, Shi-Xuan Liang, Rui-Yue Chu, Jian-Kun Dai, Feng Pan, Cheng Song

Abstract: The emerging altermagnetic RuO2 with both compensated magnetic moments and broken time-reversal symmetry possesses nontrivial magneto-electronic responses and nonrelativistic spin currents, which are closely related to magnetic easy axis. To probe the Néel order in RuO2, we conducted Ru M3-edge X-ray magnetic linear dichroism (XMLD) measurement. For epitaxial RuO2 films, characteristic XMLD signal… ▽ More The emerging altermagnetic RuO2 with both compensated magnetic moments and broken time-reversal symmetry possesses nontrivial magneto-electronic responses and nonrelativistic spin currents, which are closely related to magnetic easy axis. To probe the Néel order in RuO2, we conducted Ru M3-edge X-ray magnetic linear dichroism (XMLD) measurement. For epitaxial RuO2 films, characteristic XMLD signals can be observed in either RuO2(100) and RuO2(110) at normal incidence or RuO2(001) at oblique incidence, and the signals disappear when test temperature exceeds Néel temperature. For nonepitaxial RuO2 films, the flat lines in the XMLD patterns of RuO2(100) and RuO2(110) demonstrate that there is no in-plane uniaxial alignment of Néel order in these samples, due to the counterbalanced Néel order of the twin crystals evidenced by X-ray diffraction phi-scan measurements. Our experimental results unambiguously demonstrate the antiferromagnetism in RuO2 films and reveal the spatial relation of Néel order to be parallel with RuO2 [001] crystalline axis. These research findings would deepen our understanding of RuO2 and other attractive altermagnetic materials applied in the field of spintronics. △ Less

Submitted 22 December, 2024; originally announced December 2024.

Comments: 16 pages, 4 figures

Electrical Manipulation of Spin Splitting Torque in Altermagnetic RuO2

Authors: Yichi Zhang, Hua Bai, Lei Han, Jiankun Dai, Chong Chen, Shixuan Liang, Yanzhang Cao, Yingying Zhang, Qian Wang, Wenxuan Zhu, Feng Pan, Cheng Song

Abstract: Due to nonrelativistic altermagnetic spin splitting effect (ASSE), altermagnets can generate time-reversal-odd spin current and spin splitting torque (SST) with spin polarization parallel to the Néel vector. Hence the effective manipulation of SST would provide plenty of opportunities for designable spintronic devices, which remains elusive. Here, the electrical control of SST is achieved in alter… ▽ More Due to nonrelativistic altermagnetic spin splitting effect (ASSE), altermagnets can generate time-reversal-odd spin current and spin splitting torque (SST) with spin polarization parallel to the Néel vector. Hence the effective manipulation of SST would provide plenty of opportunities for designable spintronic devices, which remains elusive. Here, the electrical control of SST is achieved in altermagnetic RuO2, based on controllable Néel vector of RuO2 and Néel vector-dependent generation of SST. We demonstrate the current-induced switching of Néel vector via spin-orbit torque in RuO2 films, according to the reversible polarity of electrical transport measurements and X-ray magnetic linear dichroism (XMLD). The XMLD also unprecedentedly demonstrates that Néel vector really exists in altermagnets. The switching of Néel vector to the current direction and resultantly enhanced spin polarization parallel to the Néel vector brings about stronger ASSE-induced spin current. Our findings not only enrich the properties of altermagnets but also pave the way for high speed memories and nano-oscillators with excellent controllability and efficiency. △ Less

Submitted 22 December, 2024; originally announced December 2024.

Comments: 22 pages, 3 figures

Energy Efficient Stochastic Signal Manipulation in Superparamagnetic Tunnel Junctions via Voltage-Controlled Exchange Coupling

Authors: Qi Jia, Onri J. Benally, Brandon Zink, Delin Zhang, Yang Lv, Shuang Liang, Deyuan Lyu, Yu-Chia Chen, Yifei Yang, Yu Han Huang, Jian-Ping Wang

Abstract: Superparamagnetic tunnel junctions (sMTJs) are emerging as promising components for stochastic units in neuromorphic computing, owing to their tunable random switching behavior. Conventional MTJ control methods, such as spin-transfer torque (STT) and spin-orbit torque (SOT), often require substantial power. Here, we introduce the voltage-controlled exchange coupling (VCEC) mechanism, enabling swit… ▽ More Superparamagnetic tunnel junctions (sMTJs) are emerging as promising components for stochastic units in neuromorphic computing, owing to their tunable random switching behavior. Conventional MTJ control methods, such as spin-transfer torque (STT) and spin-orbit torque (SOT), often require substantial power. Here, we introduce the voltage-controlled exchange coupling (VCEC) mechanism, enabling switching between antiparallel and parallel states in sMTJs with an ultralow power consumption of only 40 nW, approximately two orders of magnitude lower than conventional STT-based sMTJs. This mechanism yields a sigmoid-shaped output response, making it ideally suited for neuromorphic computing applications. Furthermore, we validate the feasibility of integrating VCEC with the SOT current control, offering an additional dimension for magnetic state manipulation. This work marks the first practical demonstration of VCEC effect in sMTJs, highlighting its potential as a low-power control solution for probabilistic bits in advanced computing systems. △ Less

Submitted 9 December, 2024; originally announced December 2024.

Comments: 20 pages, 4 figures

Lead-free Hybrid Perovskite: An Efficient Room Temperature Spin Generator via Large Interfacial Rashba effect

Authors: Lei Han, Qian Wang, Ying Lu, Sheng Tao, Wenxuan Zhu, Xiaoyu Feng, Shixuan Liang, Hua Bai, Chong Chen, Kai Wang, Zhou Yang, Xiaolong Fan, Cheng Song, Feng Pan

Abstract: Two-dimensional (2D) hybrid organic-inorganic perovskite (HOIP) demonstates great potential for developing flexible and wearable spintronic devices, by serving as spin sources via the bulk Rashba effect (BRE). However, the practical application of BRE in 2D HOIP faces huge challenges, particularly due to the toxicity of lead, which is crucial for achieving large spin-orbit coupling, and the restri… ▽ More Two-dimensional (2D) hybrid organic-inorganic perovskite (HOIP) demonstates great potential for developing flexible and wearable spintronic devices, by serving as spin sources via the bulk Rashba effect (BRE). However, the practical application of BRE in 2D HOIP faces huge challenges, particularly due to the toxicity of lead, which is crucial for achieving large spin-orbit coupling, and the restrictions in 2D HOIP candidates to meet specific symmetry-breaking requirements. To overcome these obstacles, we design a strategy to exploit the interfacial Rashba effect (IRE) of lead-free 2D HOIP (C6H5CH2CH2NH3)2CuCl4 (PEA-CuCl), manifesting as an efficient spin generator at room temperature. IRE of PEA-CuCl originates from the large orbital hybridization at the interface between PEA-CuCl and adjacent ferromagnetic layers. Spin-torque ferromagnetic resonance measurements further quantify a large Rashba effective field of 14.04 Oe per 10^11 A m-2, surpassing those of lead-based HOIP and traditional all-inorganic heterojunctions with noble metals. Our lead-free 2D HOIP PEA-CuCl, which harnesses large IRE for spin generation, is efficient, nontoxic, and economic, offering huge promise for future flexible and wearable spintronic devices. △ Less

Submitted 24 October, 2024; originally announced October 2024.

Beam dynamics induced by the quantum metric of exceptional rings

Authors: Zhaoyang Zhang, Ismaël Septembre, Zhenzhi Liu, Pavel Kokhanchik, Shun Liang, Fu Liu, Changbiao Li, Hongxing Wang, Maochang Liu, Yanpeng Zhang, Min Xiao, Guillaume Malpuech, Dmitry Solnyshkov

Abstract: Topological physics has broadened its scope from the study of topological insulating phases to include nodal phases containing band structure singularities. The geometry of the corresponding quantum states is described by the quantum metric which provides a theoretical framework for explaining phenomena that conventional approaches fail to address. The field has become even broader by encompassing… ▽ More Topological physics has broadened its scope from the study of topological insulating phases to include nodal phases containing band structure singularities. The geometry of the corresponding quantum states is described by the quantum metric which provides a theoretical framework for explaining phenomena that conventional approaches fail to address. The field has become even broader by encompassing non-Hermitian singularities: in addition to Dirac, Weyl nodes, or nodal lines, it is now common to encounter exceptional points, exceptional or Weyl rings, and even Weyl spheres. They give access to fascinating effects that cannot be reached within the Hermitian picture. However, the quantum geometry of non-Hermitian singularities is not a straightforward extension of the Hermitian one, remaining far less understood. Here, we study experimentally and theoretically the dynamics of wave packets at exceptional rings stemming from Dirac points in a photonic honeycomb lattice. First, we demonstrate a transition between conical diffraction and non-Hermitian broadening in real space. Next, we predict and demonstrate a new non-Hermitian effect in the reciprocal space, induced by the non-orthogonality of the eigenstates. We call it transverse non-Hermitian drift, and its description requires biorthogonal quantum metric. The non-Hermitian drift can be used for applications in beam steering. △ Less

Submitted 18 October, 2024; originally announced October 2024.

Controllable and Fast Growth of High-Quality Atomically Thin and Atomically Flat Bi$_2$O$_2$Se Films

Authors: Yusen Feng, Pei Chen, Nian Li, Suzhe Liang, Ke Zhang, Minghui Xu, Yan Zhao, Jie Gong, Shu Zhang, Huaqian Leng, Yuanyuan Zhou, Yong Wang, Liang Qiao

Abstract: As a novel and promising 2D material, bismuth oxyselenide (Bi$_2$O$_2$Se) has demonstrated significant potential to overcome existing technical barriers in various electronic device applications, due to its unique physical properties like high symmetry, adjustable electronic structure, ultra-high electron mobility. However, the rapid growth of Bi$_2$O$_2$Se films down to a few atomic layers with p… ▽ More As a novel and promising 2D material, bismuth oxyselenide (Bi$_2$O$_2$Se) has demonstrated significant potential to overcome existing technical barriers in various electronic device applications, due to its unique physical properties like high symmetry, adjustable electronic structure, ultra-high electron mobility. However, the rapid growth of Bi$_2$O$_2$Se films down to a few atomic layers with precise control remains a significant challenge. In this work, the growth of two-dimensional (2D) Bi$_2$O$_2$Se thin films by the pulsed laser deposition (PLD) method is systematically investigated. By controlling temperature, oxygen pressure, laser energy density and laser emission frequency, we successfully prepare atomically thin and flat Bi$_2$O$_2$Se (001) thin films on the (001) surface of SrTiO3. Importantly, we provide a fundamental and unique perspective toward understanding the growth process of atomically thin and flat Bi$_2$O$_2$Se films, and the growth process can be primarily summarized into four steps: i) anisotropic non-spontaneous nucleation preferentially along the step roots; ii) monolayer Bi$_2$O$_2$Se nanosheets expanding across the surrounding area, and eventually covering the entire STO substrate step; iii) vertical growth of Bi$_2$O$_2$Se monolayer in a 2D Frank-van der Merwe (FM) epitaxial growth, and iv) with a layer-by-layer 2D FM growth mode, ultimately producing an atomically flat and epitaxially aligned thin film. Moreover, the combined results of the crystallinity quality, surface morphology and the chemical states manifest the successful PLD-growth of high-quality Bi$_2$O$_2$Se films in a controllable and fast mode. △ Less

Submitted 1 August, 2024; originally announced August 2024.

Optimization of submicron Ni/Au/Ge contacts to an AlGaAs/GaAs two-dimensional electron gas

Authors: Matthew Mann, James Nakamura, Shuang Liang, Tanmay Maiti, Rosa Diaz, Michael J. Manfra

Abstract: We report on fabrication and performance of submicron Ni/Au/Ge contacts to a two-dimensional electron gas in an AlGaAs/GaAs heterostructure. Utilizing scanning transmission electron microscopy, energy dispersive x-ray spectroscopy, and low temperature electrical measurements we investigate the relationship between contact performance and the mechanical and chemical properties of the annealed metal… ▽ More We report on fabrication and performance of submicron Ni/Au/Ge contacts to a two-dimensional electron gas in an AlGaAs/GaAs heterostructure. Utilizing scanning transmission electron microscopy, energy dispersive x-ray spectroscopy, and low temperature electrical measurements we investigate the relationship between contact performance and the mechanical and chemical properties of the annealed metal stack. Contact geometry and crystallographic orientation significantly impact performance. Our results indicate that the spatial distribution of germanium in the annealed contact plays a central role in the creation of high transmission contacts. We characterize the transmission of our contacts at high magnetic fields in the quantum Hall regime. Our work establishes that contacts with area 0.5 square microns and resistance less than 400 Ohms can be fabricated with high yield. △ Less

Submitted 1 August, 2024; originally announced August 2024.

Selective and Quasi-continuous Switching of Ferroelectric Chern Insulator Device for Neuromorphic Computing

Authors: Moyu Chen, Yongqin Xie, Bin Cheng, Zaizheng Yang, Xin-Zhi Li, Fanqiang Chen, Qiao Li, Jiao Xie, Kenji Watanabe, Takashi Taniguchi, Wen-Yu He, Menghao Wu, Shi-Jun Liang, Feng Miao

Abstract: Topologically protected edge state transport in quantum materials is dissipationless and features quantized Hall conductance, and shows great potential in highly fault-tolerant computing technologies. However, it remains elusive about how to develop topological edge state-based computing devices. Recently, exploration and understanding of interfacial ferroelectricity in various van der Waals heter… ▽ More Topologically protected edge state transport in quantum materials is dissipationless and features quantized Hall conductance, and shows great potential in highly fault-tolerant computing technologies. However, it remains elusive about how to develop topological edge state-based computing devices. Recently, exploration and understanding of interfacial ferroelectricity in various van der Waals heterostructure material systems have received widespread attention among the community of materials science and condensed matter physics3-11. Such ferroelectric polarization emergent at the vdW interface can coexist with other quantum states and thus provides an unprecedented opportunity to electrically switch the topological edge states of interest, which is of crucial significance to the fault-tolerant electronic device applications based on the topological edge states. Here, we report the selective and quasi-continuous ferroelectric switching of topological Chern insulator devices and demonstrate its promising application in noise-immune neuromorphic computing. We fabricate this ferroelectric Chern insulator device by encapsulating magic-angle twisted bilayer graphene with doubly-aligned h-BN layers, and observe the coexistence of the interfacial ferroelectricity and the topological Chern insulating states. This ferroelectricity exhibits an anisotropic dependence on the in-plane magnetic field. By using a VBG pulse with delicately controlled amplitude, we realize the nonvolatile switching between any pair of Chern insulating states and achieve 1280 distinguishable nonvolatile resistance levels on a single device. Furthermore, we demonstrate deterministic switching between two arbitrary levels among the record-high number of nonvolatile resistance levels. △ Less

Submitted 24 July, 2024; originally announced July 2024.

Journal ref: Nature Nanotechnolgy (2024)

Thermodynamic Space of Chemical Reaction Networks

Authors: Shiling Liang, Paolo De Los Rios, Daniel Maria Busiello

Abstract: Living systems operate out of equilibrium, continuously consuming energy to sustain organised, functional states. Their emergent behaviour usually relies on a set of interconnected chemical reaction networks (CRNs) driven by external fluxes that keep some species at fixed concentrations. Hence, uncovering the principles governing the functioning of these CRNs is crucial to understand how living sy… ▽ More Living systems operate out of equilibrium, continuously consuming energy to sustain organised, functional states. Their emergent behaviour usually relies on a set of interconnected chemical reaction networks (CRNs) driven by external fluxes that keep some species at fixed concentrations. Hence, uncovering the principles governing the functioning of these CRNs is crucial to understand how living systems generate and regulate complexity. While kinetics plays a key role in shaping detailed dynamical phenomena, the range of operations of a CRN is fundamentally constrained by thermodynamics. Here, we introduce and analytically derive the "thermodynamic space" of a CRN, i.e., the range of accessible stationary concentrations that can be realized under a given energetic budget. We establish analogous bounds for reaction affinities, shedding light on how global thermodynamic properties, such as the total non-equilibrium driving, can limit local non-equilibrium quantities. We illustrate our results in various paradigmatic examples, demonstrating how the onset of complex behaviors is intimately tangled with the presence of non-equilibrium conditions. By providing a general tool for analysing CRNs, the presented framework constitutes a stepping stone to deepen our ability to predict complex out-of-equilibrium phenomena and design artificial chemical systems, starting from the sole knowledge of the underlying thermodynamic properties. △ Less

Submitted 2 February, 2026; v1 submitted 16 July, 2024; originally announced July 2024.

Electrical switching of Ising-superconducting nonreciprocity for quantum neuronal transistor

Authors: Junlin Xiong, Jiao Xie, Bin Cheng, Yudi Dai, Xinyu Cui, Lizheng Wang, Zenglin Liu, Ji Zhou, Naizhou Wang, Xianghan Xu, Xianhui Chen, Sang-Wook Cheong, Shi-Jun Liang, Feng Miao

Abstract: Nonreciprocal quantum transport effect is mainly governed by the symmetry breaking of the material systems and is gaining extensive attention in condensed matter physics. Realizing electrical switching of the polarity of the nonreciprocal transport without external magnetic field is essential to the development of nonreciprocal quantum devices. However, electrical switching of superconducting nonr… ▽ More Nonreciprocal quantum transport effect is mainly governed by the symmetry breaking of the material systems and is gaining extensive attention in condensed matter physics. Realizing electrical switching of the polarity of the nonreciprocal transport without external magnetic field is essential to the development of nonreciprocal quantum devices. However, electrical switching of superconducting nonreciprocity remains yet to be achieved. Here, we report the observation of field-free electrical switching of nonreciprocal Ising superconductivity in Fe3GeTe2/NbSe2 van der Waals (vdW) heterostructure. By taking advantage of this electrically switchable superconducting nonreciprocity, we demonstrate a proof-of-concept nonreciprocal quantum neuronal transistor, which allows for implementing the XOR logic gate and faithfully emulating biological functionality of a cortical neuron in the brain. Our work provides a promising pathway to realize field-free and electrically switchable nonreciprocity of quantum transport and demonstrate its potential in exploring neuromorphic quantum devices with both functionality and performance beyond the traditional devices. △ Less

Submitted 20 June, 2024; originally announced June 2024.

Journal ref: Nature Communications 15, 4953 (2024)

Link between cascade transitions and correlated Chern insulators in magic-angle twisted bilayer graphene

Authors: Qianying Hu, Shu Liang, Xinheng Li, Hao Shi, Xi Dai, Yang Xu

Abstract: Chern insulators are topologically non-trivial states of matter characterized by incompressible bulk and chiral edge states. Incorporating topological Chern bands with strong electronic correlations provides a versatile playground for studying emergent quantum phenomena. In this study, we resolve the correlated Chern insulators (CCIs) in magic-angle twisted bilayer graphene (MATBG) through Rydberg… ▽ More Chern insulators are topologically non-trivial states of matter characterized by incompressible bulk and chiral edge states. Incorporating topological Chern bands with strong electronic correlations provides a versatile playground for studying emergent quantum phenomena. In this study, we resolve the correlated Chern insulators (CCIs) in magic-angle twisted bilayer graphene (MATBG) through Rydberg exciton sensing spectroscopy, and unveil their direct link with the zero-field cascade features in the electronic compressibility. The compressibility minima in the cascade are found to deviate substantially from nearby integer fillings (by $Δν$) and coincide with the onsets of CCIs in doping densities, yielding a quasi-universal relation $B_c$=$Φ_0Δν/C$ (onset magnetic field $B_c$, magnetic flux quantum $Φ_0$ and Chern number $C$). We suggest these onsets lie on the intersection where the integer filling of localized "f-orbitals" and Chern bands are simultaneously reached. Our findings update the field-dependent phase diagram of MATBG and directly support the topological heavy fermion model. △ Less

Submitted 12 June, 2024; originally announced June 2024.

Comments: 24 pages, 4 figures, supplementary material

Interfacial magnetic spin Hall effect in van der Waals Fe3GeTe2/MoTe2 heterostructure

Authors: Yudi Dai, Junlin Xiong, Yanfeng Ge, Bin Cheng, Lizheng Wang, Pengfei Wang, Zenglin Liu, Shengnan Yan, Cuiwei Zhang, Xianghan Xu, Youguo Shi, Sang-Wook Cheong, Cong Xiao, Shengyuan A. Yang, Shi-Jun Liang, Feng Miao

Abstract: The spin Hall effect (SHE) allows efficient generation of spin polarization or spin current through charge current and plays a crucial role in the development of spintronics. While SHE typically occurs in non-magnetic materials and is time-reversal even, exploring time-reversal-odd (T-odd) SHE, which couples SHE to magnetization in ferromagnetic materials, offers a new charge-spin conversion mecha… ▽ More The spin Hall effect (SHE) allows efficient generation of spin polarization or spin current through charge current and plays a crucial role in the development of spintronics. While SHE typically occurs in non-magnetic materials and is time-reversal even, exploring time-reversal-odd (T-odd) SHE, which couples SHE to magnetization in ferromagnetic materials, offers a new charge-spin conversion mechanism with new functionalities. Here, we report the observation of giant T-odd SHE in Fe3GeTe2/MoTe2 van der Waals heterostructure, representing a previously unidentified interfacial magnetic spin Hall effect (interfacial-MSHE). Through rigorous symmetry analysis and theoretical calculations, we attribute the interfacial-MSHE to a symmetry-breaking induced spin current dipole at the vdW interface. Furthermore, we show that this linear effect can be used for implementing multiply-accumulate operations and binary convolutional neural networks with cascaded multi-terminal devices. Our findings uncover an interfacial T-odd charge-spin conversion mechanism with promising potential for energy-efficient in-memory computing. △ Less

Submitted 26 March, 2024; originally announced March 2024.

Journal ref: Nature Communications 15, 1129 (2024)

Thermal Tensor Network Approach for Spin-Lattice Relaxation in Quantum Magnets

Authors: Ning Xi, Yuan Gao, Chengchen Li, Shuang Liang, Rong Yu, Xiaoqun Wang, Wei Li

Abstract: Low-dimensional quantum magnets, particularly those with strong spin frustration, are characterized by their notable spin fluctuations. Nuclear magnetic resonance (NMR) serves as a sensitive probe of low-energy fluctuations that offers valuable insight into rich magnetic phases and emergent phenomena in quantum magnets. Although experimentally accessible, the numerical simulation of NMR relaxation… ▽ More Low-dimensional quantum magnets, particularly those with strong spin frustration, are characterized by their notable spin fluctuations. Nuclear magnetic resonance (NMR) serves as a sensitive probe of low-energy fluctuations that offers valuable insight into rich magnetic phases and emergent phenomena in quantum magnets. Although experimentally accessible, the numerical simulation of NMR relaxation rates, specifically the spin-lattice relaxation rate $1/T_1$, remains a significant challenge. Analytical continuation based on Monte Carlo calculations are hampered by the notorious negative sign for frustrated systems, and the real-time simulations incur significant costs to capture low-energy fluctuations. Here we propose computing the relaxation rate using thermal tensor networks (TTNs), which provides a streamlined approach by calculating its imaginary-time proxy. We showcase the accuracy and versatility of our methodology by applying it to one-dimensional spin chains and two-dimensional lattices, where we find that the critical exponents $η$ and $zν$ can be extracted from the low-temperature scalings of the simulated $1/T_1$ near quantum critical points. Our results also provide insights into the low-dimensional and frustrated magnetic materials, elucidating universal scaling behaviors in the Ising chain compound CoNb$_2$O$_6$ and revealing the renormalized classical behaviors in the triangular-lattice antiferromagnet Ba$_8$CoNb$_6$O$_{24}$. We apply the approach to effective model of the family of frustrated magnets AYbCh$_2$ (A = Na, K, Cs, and Ch = O, S, Se), and find dramatic changes from spin ordered to the proposed quantum spin liquid phase. Overall, with high reliability and accuracy, the TTN methodology offers a systematic strategy for studying the intricate dynamics observed across a broad spectrum of quantum magnets and related fields. △ Less

Submitted 20 March, 2024; v1 submitted 18 March, 2024; originally announced March 2024.

Comments: 15 pages, 12 figures

Zero modes of velocity field and topological invariant in quantum torus

Authors: Annan Fan, Shi-Dong Liang

Abstract: We propose the velocity field approach to characterize topological invariants of quantum states. We introduce the indexes of the velocity field flow based on the zero modes of the velocity field and find that these zero modes play the role of effective topological charges or defects linking to Euler characteristic by the Poincaré-Hopf theorem. The global property of the indexes is topological inva… ▽ More We propose the velocity field approach to characterize topological invariants of quantum states. We introduce the indexes of the velocity field flow based on the zero modes of the velocity field and find that these zero modes play the role of effective topological charges or defects linking to Euler characteristic by the Poincaré-Hopf theorem. The global property of the indexes is topological invariants against the parameter deformation. We demonstrate this approach by the quantum torus model and compare the topological invariant with that obtained from the Chern number. We find that the physical mechanism of the topological invariant based on the zero modes of the velocity field is different from that of the topological invariant by the Chern number. The topological invariant characterized by the velocity field describes a homeomorphic topological invariant associated with the zero modes on the submanifold of the base manifold of the SU(2)-fibre bundle for quantum torus, whereas the Chern number characterizes a homotopy invariant associated with the exceptional points in the Brillouin zone. We also propose the generalized winding number in terms of the velocity field for both Hermitian and non-Hermitian systems. This gives a connection between the zero mode and winding number in the velocity space. These results enrich the topological invariants of quantum states and promises us a novel insight to understanding topological invariants of quantum states as well as expected to be further applied in more generic models. △ Less

Submitted 13 March, 2024; originally announced March 2024.

Comments: 13 pages, 2 figures

Journal ref: Results in Physics 31 (2021) 104912