Showing 1–50 of 599 results for author: liu, m

Phase transition revealed by eigen microstate entropy

Authors: Teng Liu, Xuezhi Niu, Mingli Zhang, Gaoke Hu, Yuhan Chen, Yongwen Zhang, Rui Shi, Jingyuan Li, Peng Tan, Maoxin Liu, Hui Li, Xiaosong Chen

Abstract: We introduce the eigen microstate entropy ($S_{\text{EM}}$), a novel metric of complexity derived from the probabilities of statistically independent eigen microstates. After establishing its scaling behavior in equilibrium systems and demonstrating its utility in critical phenomena (mean spherical, Ising, and Potts models), we apply $S_{\text{EM}}$ to non-equilibrium complex systems. Our analysis… ▽ More We introduce the eigen microstate entropy ($S_{\text{EM}}$), a novel metric of complexity derived from the probabilities of statistically independent eigen microstates. After establishing its scaling behavior in equilibrium systems and demonstrating its utility in critical phenomena (mean spherical, Ising, and Potts models), we apply $S_{\text{EM}}$ to non-equilibrium complex systems. Our analysis reveals a consistent precursor signal: a significant increase in $S_{\text{EM}}$ precedes major phase transitions. Specifically, we observe this entropy rise before biomolecular condensate formation in liquid-liquid phase separation in living cells and months ahead of El Niño events. These findings position $S_{\text{EM}}$ as a general framework for detecting and interpreting phase transitions in non-equilibrium systems. △ Less

Submitted 28 December, 2025; originally announced December 2025.

Gate-Tunable Transport and 1D Channel in a Graphene Nanoslide

Authors: Christophe De Beule, Ming-Hao Liu, Bart Partoens, Lucian Covaci

Abstract: We present a theory of the graphene nanoslide, a fundamental device for graphene straintronics that realizes a single pseudogauge barrier. We solve the scattering problem in closed form and demonstrate that the nanoslide gives rise to a hybrid pseudogauge and electrostatic cavity in the bipolar regime, and hosts one-dimensional transverse channels. The latter can be tuned using a bottom gate betwe… ▽ More We present a theory of the graphene nanoslide, a fundamental device for graphene straintronics that realizes a single pseudogauge barrier. We solve the scattering problem in closed form and demonstrate that the nanoslide gives rise to a hybrid pseudogauge and electrostatic cavity in the bipolar regime, and hosts one-dimensional transverse channels. The latter can be tuned using a bottom gate between valley chiral or counterpropagating modes, as well as one-dimensional flatbands. Hence, the local density of states near the barrier depends strongly on the gate voltage with a tunable sublattice and electron-hole asymmetry. In the presence of electron-electron interactions, the nanoslide allows for in-situ tuning between a chiral and ordinary Tomonaga-Luttinger liquid. △ Less

Submitted 28 December, 2025; originally announced December 2025.

Comments: 6 + 12 pages, 4 + 1 figures

Nucleation suppression by charge screening on grain boundaries: a kinetic model for bulk imprint in polycrystalline ferroelectric thin films

Authors: Huanhuan Tian, Jianguo Yang, Ming Liu

Abstract: The imprint effect, a significant reliability challenge in ferroelectric memories, manifests as a shift in the coercive field during retention and endurance tests, ultimately degrading the usable memory window. \rv{While traditional models attribute imprint primarily to charge screening at the interface between the dead layer and the ferroelectric film, the contribution from grain boundaries has b… ▽ More The imprint effect, a significant reliability challenge in ferroelectric memories, manifests as a shift in the coercive field during retention and endurance tests, ultimately degrading the usable memory window. \rv{While traditional models attribute imprint primarily to charge screening at the interface between the dead layer and the ferroelectric film, the contribution from grain boundaries has been largely overlooked. This work advances a bulk imprint mechanism by establishing a phase-field model, which demonstrates that the tuning of domain nuclei near grain boundaries via charge screening consistently explains the imprint process and aligns with key experimental trends.} These findings provide novel insights into the imprint process and advance the understanding of reliability issues in ferroelectric memory devices. △ Less

Submitted 14 December, 2025; originally announced December 2025.

Anisotropic transport in ballistic bilayer graphene cavities

Authors: Florian Schoeppl, Alina Mrenca-Kolasinska, Ming-Hao Liu, Korbinian Schwarzmaier, Klaus Richter, Angelika Knothe

Abstract: Closing the gap between ray tracing simulations and experimentally observed electron jetting in bilayer graphene (BLG), we study all-electronic, gate-defined BLG cavities using tight-binding simulations and semiclassical equations of motion. Such cavities offer a rich playground to investigate anisotropic electron transport due to the trigonally warped Fermi surfaces. In this work, we achieve two… ▽ More Closing the gap between ray tracing simulations and experimentally observed electron jetting in bilayer graphene (BLG), we study all-electronic, gate-defined BLG cavities using tight-binding simulations and semiclassical equations of motion. Such cavities offer a rich playground to investigate anisotropic electron transport due to the trigonally warped Fermi surfaces. In this work, we achieve two things: First, we verify the existence of triangular modes (as predicted by classical ray tracing calculations) in the quantum solutions of closed circular BLG cavities. Then, we explore signatures of said triangular modes in transport through open BLG cavities connected to leads. We show that the triangular symmetry translates into anisotropic transport and present an optimal setup for experimental detection of the triangular modes as well as for controlled modulation of transport in preferred directions. △ Less

Submitted 9 December, 2025; originally announced December 2025.

Accelerating discovery of infrared nonlinear optical materials with large shift current via high-throughput screening

Authors: Aiqin Yang, Dian Jin, Mingkang Liu, Daye Zheng, Qi Wang, Qiangqiang Gu, Jian-Hua Jiang

Abstract: Discovering nonlinear optical (NLO) materials with strong shift current response, particularly in the infrared (IR) regime, is essential for next-generation optoelectronics yet remains highly challenging in both experiments and theory, which still largely relies on case by case studies. Here, we employ a high-throughput screening strategy, applying a multi-step filter to the Materials Project data… ▽ More Discovering nonlinear optical (NLO) materials with strong shift current response, particularly in the infrared (IR) regime, is essential for next-generation optoelectronics yet remains highly challenging in both experiments and theory, which still largely relies on case by case studies. Here, we employ a high-throughput screening strategy, applying a multi-step filter to the Materials Project database (>154,000 materials), which yielded 2,519 candidate materials for detailed first-principle evaluation. From these calculations, we identify 32 NLO materials with strong shift current response ($σ$ > 100 $μA/V^2$). Our work reveals that layered structures with $C_{3v}$ symmetry and heavy $p$-block elements (e.g. Te, Sb) exhibit apparent superiority in enhancing shift current. More importantly, 9 of these compounds show shift current response peaks in the IR region, with the strongest reaching 616 $μA/V^2$, holding significant application potential in fields such as IR photodetection, sensing, and energy harvesting. Beyond identifying promising candidates, this work establishes a comprehensive and high-quality first-principles dataset for NLO response, providing a solid foundation for future AI-driven screening and accelerated discovery of high-performance NLO materials, as demonstrated by a prototype machine-learning application. △ Less

Submitted 4 December, 2025; originally announced December 2025.

Increase of critical current density in FeSe superconductor by strain effect

Authors: Han Luo, Xinyue Wang, Xin Zhou, Longfei Sun, Mengqin Liu, Ran Guo, Sheng Li, Yue Sun, Zhixiang Shi

Abstract: Conventional $J_c$-enhancement methods like doping and irradiation often introduce extrinsic elements or defects, altering intrinsic properties. Here, we report a significant $J_c$ enhancement in FeSe single crystals through compressive strain applied using a glass-fiber-reinforced plastic substrate with anisotropic thermal contraction during cooling. Under zero field at 2 K, $J_{\text{c}}$ increa… ▽ More Conventional $J_c$-enhancement methods like doping and irradiation often introduce extrinsic elements or defects, altering intrinsic properties. Here, we report a significant $J_c$ enhancement in FeSe single crystals through compressive strain applied using a glass-fiber-reinforced plastic substrate with anisotropic thermal contraction during cooling. Under zero field at 2 K, $J_{\text{c}}$ increases by a factor of $\sim$4 from $\sim 2.3 \times 10^{4}$ to $\sim 8.7 \times 10^{4}$ A cm$^{-2}$; at 5 T, it achieves an order-of-magnitude enhancement, rising from $\sim 1.0 \times 10^{3}$ to $\sim 1.0 \times 10^{4}$ A cm$^{-2}$. Analysis based on the Dew-Hughes model of the $f_{\text{p}}$(h) relationship shows that strain strengthens vortex pinning, and shifts the pinning mechanism from point-like pinning to combined point and surface pinnings. This work offers an effective method to enhance FeSe's current-carrying limitation, deepens understanding of iron-based superconductors' pinning mechanisms, and highlights strain engineering's potential for optimizing superconducting performance. △ Less

Submitted 24 November, 2025; originally announced November 2025.

Comments: 8 pages, 4 figures

Journal ref: Supercond. Sci. Technol. 38 115004 (2025)

Lessons from $α$-RuCl3 for pursuing quantum spin liquid physics in atomically thin materials

Authors: Claudia Ojeda-Aristizabal, Xiaohu Zheng, Changsong Xu, Zohar Nussinov, Yukitoshi Motome, Arnab Banerjee, Adam W. Tsen, Michael Knap, Rui-Rui Du, Gajadhar Joshi, Andy Mounce, Youngwook Kim, Benjamin M. Hunt, Dmitry Shcherbakov, Boyi Zhou, Ran Jing, Mengkun Liu, Hui Zhao, Bolin Liao, Martin Claassen, Onur Erten, Yong P. Chen, Erik A. Henriksen

Abstract: Quantum spin liquids can arise from Kitaev magnetic interactions, and exhibit fractionalized excitations with the potential for a topological form of quantum computation. This review surveys recent experimental and theoretical progress on the pursuit of phenomena related to Kitaev magnetism in layered and exfoliatable materials, which offer numerous opportunities to apply powerful techniques from… ▽ More Quantum spin liquids can arise from Kitaev magnetic interactions, and exhibit fractionalized excitations with the potential for a topological form of quantum computation. This review surveys recent experimental and theoretical progress on the pursuit of phenomena related to Kitaev magnetism in layered and exfoliatable materials, which offer numerous opportunities to apply powerful techniques from the field of atomically thin materials. We primarily focus on the antiferromagnetic Mott insulator $α$-RuCl3, which exhibits Kitaev couplings and is readily exfoliated to single- or few-layer sheets, and thus serves as a test bed for developing probes of Kitaev phenomena in atomically thin materials and devices. We introduce the Kitaev model and how it is realized in $α$-RuCl3 and other material candidates; and cover $α$-RuCl3 synthesis and fabrication into van der Waals heterostructure devices. A key discovery is a work-function-mediated charge transfer that heavily dopes both the $α$-RuCl3 and proximate materials, and can enhance Kitaev interactions by up to 50%. We further discuss a wide range of recent results in electronic transport and optical and tunneling spectroscopies of $α$-RuCl3 devices. The experimental techniques and theoretical insights developed for $α$-RuCl3 establish a framework for discovering and engineering superior two-dimensional Kitaev materials that may ultimately realize elusive quantum spin liquid phases. △ Less

Submitted 17 November, 2025; originally announced November 2025.

Comments: 53 pages, 27 figures

Benchmarking GNNs for OOD Materials Property Prediction with Uncertainty Quantification

Authors: Liqin Tan, Pin Chen, Menghan Liu, Xiean Wang, Jianhuan Cen, Qingsong Zou

Abstract: We present MatUQ, a benchmark framework for evaluating graph neural networks (GNNs) on out-of-distribution (OOD) materials property prediction with uncertainty quantification (UQ). MatUQ comprises 1,375 OOD prediction tasks constructed from six materials datasets using five OFM-based and a newly proposed structure-aware splitting strategy, SOAP-LOCO, which captures local atomic environments more e… ▽ More We present MatUQ, a benchmark framework for evaluating graph neural networks (GNNs) on out-of-distribution (OOD) materials property prediction with uncertainty quantification (UQ). MatUQ comprises 1,375 OOD prediction tasks constructed from six materials datasets using five OFM-based and a newly proposed structure-aware splitting strategy, SOAP-LOCO, which captures local atomic environments more effectively. We evaluate 12 representative GNN models under a unified uncertainty-aware training protocol that combines Monte Carlo Dropout and Deep Evidential Regression (DER), and introduce a novel uncertainty metric, D-EviU, which shows the strongest correlation with prediction errors in most tasks. Our experiments yield two key findings. First, the uncertainty-aware training approach significantly improves model prediction accuracy, reducing errors by an average of 70.6\% across challenging OOD scenarios. Second, the benchmark reveals that no single model dominates universally: earlier models such as SchNet and ALIGNN remain competitive, while newer models like CrystalFramer and SODNet demonstrate superior performance on specific material properties. These results provide practical insights for selecting reliable models under distribution shifts in materials discovery. △ Less

Submitted 12 November, 2025; originally announced November 2025.

Comments: 12 pages, 1 figure, 5 tables

Defect-Mediated Phase Engineering of 2D Ag at the Graphene/SiC Interface

Authors: Arpit Jain, Boyang Zheng, Sawani Datta, Kanchan Ulman, Jakob Henz, Matthew Wei-Jun Liu, Van Dong Pham, Wen He, Chengye Dong, Li-Syuan Lu, Alexander Vera, Nader Sawtarie, Wesley Auker, Ke Wang, Bob Hengstebeck, Zachary W. Henshaw, Shreya Mathela, Maxwell Wetherington, William H. Blades, Kenneth Knappenberger, Ursula Wurstbauer, Su Ying Quek, Ulrich Starke, Shengxi Huang, Vincent H. Crespi , et al. (1 additional authors not shown)

Abstract: Atomically thin silver (Ag) films offer unique opportunities in plasmonic, quantum optics, and energy harvesting, yet conventional growth methods struggle to achieve structural control at the monolayer limit. Here, we demonstrate phase-selective synthesis of large-area, crystalline 2D Ag films via defect-engineered confinement heteroepitaxy (CHet) at the epitaxial graphene/silicon carbide (EG/SiC)… ▽ More Atomically thin silver (Ag) films offer unique opportunities in plasmonic, quantum optics, and energy harvesting, yet conventional growth methods struggle to achieve structural control at the monolayer limit. Here, we demonstrate phase-selective synthesis of large-area, crystalline 2D Ag films via defect-engineered confinement heteroepitaxy (CHet) at the epitaxial graphene/silicon carbide (EG/SiC) interface. By tuning graphene growth and post-growth defect introduction, two distinct Ag phases are achieved with disparate properties: a nearly commensurate Ag(1) lattice stabilized by vacancy and line defects in epitaxial graphene, and a denser Ag(2) phase preferentially grown with sp3-rich zero-layer graphene. Structural and spectroscopic characterization confirm lattice registry with the SiC substrate, while theoretical calculations reveal a thermodynamic preference for Ag(2) but an easier nucleation for Ag(1). Both phases are found to be semiconducting, with the Ag(2) phase exhibiting slightly enhanced n-doping of graphene. Notably, nonlinear optical measurements reveal a three-order magnitude difference in second-order susceptibility between the two phases, demonstrating promise for phase-tunable 2D metals in reconfigurable optoelectronic and metamaterial platforms. △ Less

Submitted 10 November, 2025; originally announced November 2025.

Discrete Differential Geometry for Simulating Nonlinear Behaviors of Flexible Systems: A Survey

Authors: Dezhong Tong, Andrew Choi, Jiaqi Wang, Weicheng Huang, Zexiong Chen, Jiahao Li, Xiaonan Huang, Mingchao Liu, Huajian Gao, K. Jimmy Hsia

Abstract: Flexible slender structures such as rods, ribbons, plates, and shells exhibit extreme nonlinear responses bending, twisting, buckling, wrinkling, and self contact, that defy conventional simulation frameworks. Discrete Differential Geometry (DDG) has emerged as a geometry first, structure preserving paradigm for modeling such behaviors. Unlike finite element or mass spring methods, DDG discretizes… ▽ More Flexible slender structures such as rods, ribbons, plates, and shells exhibit extreme nonlinear responses bending, twisting, buckling, wrinkling, and self contact, that defy conventional simulation frameworks. Discrete Differential Geometry (DDG) has emerged as a geometry first, structure preserving paradigm for modeling such behaviors. Unlike finite element or mass spring methods, DDG discretizes geometry rather than governing equations, allowing curvature, twist, and strain to be defined directly on meshes. This approach yields robust large deformation dynamics, accurate handling of contact, and differentiability essential for inverse design and learning based control. This review consolidates the rapidly expanding landscape of DDG models across 1D and 2D systems, including discrete elastic rods, ribbons, plates, and shells, as well as multiphysics extensions to contact, magnetic actuation, and fluid structure interaction. We synthesize applications spanning mechanics of nonlinear instabilities, biological morphogenesis, functional structures and devices, and robotics from manipulation to soft machines. Compared with established approaches, DDG offers a unique balance of geometric fidelity, computational efficiency, and algorithmic differentiability, bridging continuum rigor with real time, contact rich performance. We conclude by outlining opportunities for multiphysics coupling, hybrid physics data pipelines, and scalable GPU accelerated solvers, and by emphasizing DDG role in enabling digital twins, sim to real transfer, and intelligent design of next generation flexible systems. △ Less

Submitted 20 October, 2025; originally announced October 2025.

Comments: 26 pages, 8 figures

Facet Specific Electron Conduction in Pentavalent (W5+) WO3 Drives Superior Photocatalytic CO 2 Reduction in (002) Plane

Authors: Muhammad Rizwan Kamal, Mohammad Z. Rahman, Amil Aligayev, Min Liu, Li Zhong, Pengfei Xia, Yueheng Li, Yue Ruan, Xia Xiang, Pir Muhammad Ismail, Qaisar Alam, Ahmed Ismail, Muhammad Zahid, Xiaoqiang Wu, Abdullah N. Alodhayb, Qing Huang, Raj Wali Khan, Fazal Raziq, Sharafat Ali, Liang Qiao

Abstract: This article reports a concept of heat-induced topological modifications of non-layered WO 3 followed by successful synthesis of oxygen-vacant more-porous nanosheets with exposed active (002) facet. Experimental measurements and Density Functional Theory (DFT) calculations have revealed that the photoexcited electrons are found to accumulate preferentially on (002) facet to yield enhanced electron… ▽ More This article reports a concept of heat-induced topological modifications of non-layered WO 3 followed by successful synthesis of oxygen-vacant more-porous nanosheets with exposed active (002) facet. Experimental measurements and Density Functional Theory (DFT) calculations have revealed that the photoexcited electrons are found to accumulate preferentially on (002) facet to yield enhanced electron conduction, and consequently, strengthen the reduction potential as active catalytic sites for photocatalytic CO2 reduction. Owing to these beneficial properties, the more-porous nanosheets of WO 3 with (002) facet have exhibited superior performance than that of less-porous nanosheets of WO3 with (220) facet and bulk WO3 with (205) facet. This study therefore provides a new understanding of regulating physical, optical, and electronic properties through intricate atomic structure modulation of WO3, and may find widespread application in optoelectronics, sensors, and energy conversion. △ Less

Submitted 17 October, 2025; originally announced October 2025.

Nitrogen-Triggered Amorphization Enables High-Performance Solid-State Electrolytes

Authors: Bolong Hong, Lei Gao, Bingkai Zhang, Pengfei Nan, Ruishan Zhang, Yuhang Li, Zhihao Lei, Ming Liu, Jing Wu, Longbang Di, Haijin Ni, Songbai Han, Jinlong Zhu

Abstract: Amorphous solid-state electrolytes (SSEs) hold great promise for advancing the application of all-solid-state batteries (ASSBs), owing to their favorable ionic conductivity, structural tunability, and promising electrochemical performance. However, the absence of universal design principles for amorphous SSEs limits their development. By fundamentally re-evaluating the amorphization-forming abilit… ▽ More Amorphous solid-state electrolytes (SSEs) hold great promise for advancing the application of all-solid-state batteries (ASSBs), owing to their favorable ionic conductivity, structural tunability, and promising electrochemical performance. However, the absence of universal design principles for amorphous SSEs limits their development. By fundamentally re-evaluating the amorphization-forming ability of amorphous SSE systems, this study establishes a nitrogen-driven universal strategy to convert diverse metal chlorides into amorphous xLi3N-MCly (0.3 < 3x < 1.9; M denotes a metal element; 2 < y < 5) SSE. Nitrogen synergistically disrupts crystalline order via distorted coordination polyhedra and N-bridged networks, while dynamic bond reorganization enables rapid Li+ migration, achieving ionic conductivity of 2.02 mS cm-1 for 0.533Li3N-HfCl4 at 25 °C. Structural-property relationships reveal that high charge density and bridging capability of N3- enhance network disorder, shorten metal coordinating atom distances, and optimize Li+ diffusion pathway connectivity. ASSBs employing 0.533Li3N-HfCl4 retain 81.87% capacity after 2000 cycles at 1000 mA g-1 with high cathode loading (6.24 mg cm-2), demonstrating engineering viability. This work provides a paradigm for rational design of high-performance amorphous SSEs. △ Less

Submitted 10 October, 2025; originally announced October 2025.

Comments: 31 pages, 5 figures

ACM Class: A.0

Guided Diffusion for the Discovery of New Superconductors

Authors: Pawan Prakash, Jason B. Gibson, Zhongwei Li, Gabriele Di Gianluca, Juan Esquivel, Eric Fuemmeler, Benjamin Geisler, Jung Soo Kim, Adrian Roitberg, Ellad B. Tadmor, Mingjie Liu, Stefano Martiniani, Gregory R. Stewart, James J. Hamlin, Peter J. Hirschfeld, Richard G. Hennig

Abstract: The inverse design of materials with specific desired properties, such as high-temperature superconductivity, represents a formidable challenge in materials science due to the vastness of chemical and structural space. We present a guided diffusion framework to accelerate the discovery of novel superconductors. A DiffCSP foundation model is pretrained on the Alexandria Database and fine-tuned on 7… ▽ More The inverse design of materials with specific desired properties, such as high-temperature superconductivity, represents a formidable challenge in materials science due to the vastness of chemical and structural space. We present a guided diffusion framework to accelerate the discovery of novel superconductors. A DiffCSP foundation model is pretrained on the Alexandria Database and fine-tuned on 7,183 superconductors with first principles derived labels. Employing classifier-free guidance, we sample 200,000 structures, which lead to 34,027 unique candidates. A multistage screening process that combines machine learning and density functional theory (DFT) calculations to assess stability and electronic properties, identifies 773 candidates with DFT-calculated $T_\mathrm{c}>5$ K. Notably, our generative model demonstrates effective property-driven design. Our computational findings were validated against experimental synthesis and characterization performed as part of this work, which highlighted challenges in sparsely charted chemistries. This end-to-end workflow accelerates superconductor discovery while underscoring the challenge of predicting and synthesizing experimentally realizable materials. △ Less

Submitted 29 September, 2025; originally announced September 2025.

Comments: 13 pages, 5 figures, 1 table

Collective transport efficiency of microswimmer swarms optimized by tactic run-tumble dynamics

Authors: Maggie Liu, Arnold J. T. M. Mathijssen

Abstract: The collective motion of microorganisms and microrobots can be used for particle delivery, especially when guided by external magnetic fields, phototaxis, or chemotaxis. This cargo transport is enhanced significantly by hydrodynamic entrainment, where the surrounding fluid and any dissolved molecules or suspended cargo particles are dragged along with a collectively moving swarm. However, it remai… ▽ More The collective motion of microorganisms and microrobots can be used for particle delivery, especially when guided by external magnetic fields, phototaxis, or chemotaxis. This cargo transport is enhanced significantly by hydrodynamic entrainment, where the surrounding fluid and any dissolved molecules or suspended cargo particles are dragged along with a collectively moving swarm. However, it remains unclear how this directed entrainment is affected by stochastic run-tumble motion, and how such motility patterns couple to particle dispersion. Here, we combine theory and simulations to compute the entrainment velocity and diffusivity for different degrees of swimmer directedness. Surprisingly, we find that the transport efficiency Péclet number, the ratio of advective to diffusive transport, is optimal for intermediate directedness values, so perfectly guided active suspensions perform worse than those with stochastic reorientations. These results could have implications for microrobotic drug delivery and nutrient transport in microbial environments. △ Less

Submitted 29 September, 2025; originally announced September 2025.

All that structure matches does not glitter

Authors: Maya M. Martirossyan, Thomas Egg, Philipp Hoellmer, George Karypis, Mark Transtrum, Adrian Roitberg, Mingjie Liu, Richard G. Hennig, Ellad B. Tadmor, Stefano Martiniani

Abstract: Generative models for materials, especially inorganic crystals, hold potential to transform the theoretical prediction of novel compounds and structures. Advancement in this field depends on robust benchmarks and minimal, information-rich datasets that enable meaningful model evaluation. This paper critically examines common datasets and reported metrics for a crystal structure prediction task… ▽ More Generative models for materials, especially inorganic crystals, hold potential to transform the theoretical prediction of novel compounds and structures. Advancement in this field depends on robust benchmarks and minimal, information-rich datasets that enable meaningful model evaluation. This paper critically examines common datasets and reported metrics for a crystal structure prediction task$\unicode{x2014}$generating the most likely structures given the chemical composition of a material. We focus on three key issues: First, materials datasets should contain unique crystal structures; for example, we show that the widely-utilized carbon-24 dataset only contains $\approx$40% unique structures. Second, materials datasets should not be split randomly if polymorphs of many different compositions are numerous, which we find to be the case for the perov-5 and MP-20 datasets. Third, benchmarks can mislead if used uncritically, e.g., reporting a match rate metric without considering the structural variety exhibited by identical building blocks. To address these oft-overlooked issues, we introduce several fixes. We provide revised versions of the carbon-24 dataset: one with duplicates removed, one deduplicated and split by number of atoms $N$, one with enantiomorphs, and two containing only identical structures but with different unit cells. We also propose new splits for datasets with polymorphs, ensuring that polymorphs are grouped within each split subset, setting a more sensible standard for benchmarking model performance. Finally, we present METRe and cRMSE, new model evaluation metrics that can correct existing issues with the match rate metric. △ Less

Submitted 3 December, 2025; v1 submitted 15 September, 2025; originally announced September 2025.

Comments: Accepted at Thirty-Ninth Annual Conference on Neural Information Processing Systems (NeurIPS)

Inverse Elastica: A Theoretical Framework for Inverse Design of Morphing Slender Structures

Authors: JiaHao Li, Weicheng Huang, YinBo Zhu, Luxia Yu, Xiaohao Sun, Mingchao Liu, HengAn Wu

Abstract: Inverse design of morphing slender structures with programmable curvature has significant applications in various engineering fields. Most existing studies formulate it as an optimization problem, which requires repeatedly solving the forward equations to identify optimal designs. Such methods, however, are computationally intensive and often susceptible to local minima issues. In contrast, solvin… ▽ More Inverse design of morphing slender structures with programmable curvature has significant applications in various engineering fields. Most existing studies formulate it as an optimization problem, which requires repeatedly solving the forward equations to identify optimal designs. Such methods, however, are computationally intensive and often susceptible to local minima issues. In contrast, solving the inverse problem theoretically, which can bypass the need for optimizations, is highly efficient yet remains challenging, particularly for cases involving arbitrary boundary conditions (BCs). Here, we develop a systematic theoretical framework, termed inverse elastica, for the direct determination of the undeformed configuration from a target deformed shape along with prescribed BCs. Building upon the classical elastica, inverse elastica is derived by supplementing the geometric equations of undeformed configurations. The framework shows three key features: reduced nonlinearity, solution multiplicity, and inverse loading. These principles are demonstrated through two representative models: an analytical solution for a two-dimensional arc and a numerical continuation study of the inverse loading of a three-dimensional helical spring. Furthermore, we develop a theory-assisted optimization strategy for cases in which the constrains of the undeformed configurations cannot be directly formulated as BCs. Using this strategy, we achieve rational inverse design of complex spatial curves and curve-discretized surfaces with varying Gaussian curvatures. Our theoretical predictions are validated through both discrete elastic rod simulations and experiments. △ Less

Submitted 27 August, 2025; originally announced August 2025.

Comments: 29 pages, 11 figures

Atomistic mechanisms of phase transitions in all-temperature barocaloric material KPF$_6$

Authors: Jiantao Wang, Yi-Chi Zhang, Yan Liu, Hongkun Deng, Mingfeng Liu, Yan Sun, Bing Li, Xing-Qiu Chen, Peitao Liu

Abstract: Conventional barocaloric materials typically exhibit limited operating temperature ranges. In contrast, KPF$_6$ has recently been reported to achieve an exceptional all-temperature barocaloric effect (BCE) via pressure-driven phase transitions. Here, we elucidate the atomistic mechanisms underlying the phase transitions through first-principles calculations and machine-learning potential accelerat… ▽ More Conventional barocaloric materials typically exhibit limited operating temperature ranges. In contrast, KPF$_6$ has recently been reported to achieve an exceptional all-temperature barocaloric effect (BCE) via pressure-driven phase transitions. Here, we elucidate the atomistic mechanisms underlying the phase transitions through first-principles calculations and machine-learning potential accelerated molecular dynamics simulations. We identify four distinct phases: the room-temperature cubic (C) plastic crystal characterized by strong fluorine orientational disorder (FOD) and anharmonicity, the intermediate-temperature monoclinic (M-II) phase with decreasing FOD, the low-temperature monoclinic (M-I) phase with suppressed FOD, and the fully ordered rhombohedral (R) phase under pressure. Phonon calculations confirm the dynamic stability of the M-II, M-I, and R phases at 0 K, whereas the C phase requires thermal fluctuations for stabilization. Under pressure, all the C, M-II, and M-I phases transform to the R phase, which are driven by cooperative PF$_6$ octahedral rotations coupled with lattice modulations. These pressure-induced phase transitions result in persistent isothermal entropy changes across a wide temperature range, thereby explaining the experimentally observed all-temperature BCE in this material. Hybrid functional calculations reveal wide-bandgap insulating behavior across all phases. This work deciphers the interplay between FOD, anharmonicity, and phase transitions in KPF$_6$, providing important insights for the design of BCE materials with broad operational temperature spans. △ Less

Submitted 19 August, 2025; originally announced August 2025.

Comments: 16 pages, 15 figures, 4 tables (including Supplemental Material)

Journal ref: Journal of Materials Science & Technology 263 (2026) 211-219

FastTrack: a fast method to evaluate mass transport in solid leveraging universal machine learning interatomic potential

Authors: Hanwen Kang, Tenglong Lu, Zhanbin Qi, Jiandong Guo, Sheng Meng, Miao Liu

Abstract: We introduce a rapid, accurate framework for computing atomic migration barriers in crystals by combining universal machine learning force fields (MLFFs) with 3D potential energy surface sampling and interpolation. Our method suppresses periodic self interactions via supercell expansion, builds a continuous PES from MLFF energies on a spatial grid, and extracts minimum energy pathways without pred… ▽ More We introduce a rapid, accurate framework for computing atomic migration barriers in crystals by combining universal machine learning force fields (MLFFs) with 3D potential energy surface sampling and interpolation. Our method suppresses periodic self interactions via supercell expansion, builds a continuous PES from MLFF energies on a spatial grid, and extracts minimum energy pathways without predefined NEB images. Across twelve benchmark electrode and electrolyte materials including LiCoO2, LiFePO4, and LGPS our MLFF-derived barriers lie within tens of meV of DFT and experiment, while achieving ~10^2 x speedups over DFT-NEB. We benchmark GPTFF, CHGNet, and MACE, show that fine-tuning on PBE/PBE+U data further enhances accuracy, and provide an open-source package for high-throughput materials screening and interactive PES visualization. △ Less

Submitted 14 August, 2025; originally announced August 2025.

Journal ref: AI Sci. 1 015004 (2025)

Giant spin Hall effects and topological surface states in ternary-layered MAX carbides Mn+1AlCn (M= Nb, Ta, n=1, 2, 3)

Authors: Yanhui Chen, Hong-Yan Lu, Wenjin Yang, Meifeng Liu, Bin Cui, Desheng Liu, Bing Huang, Xi Zuo

Abstract: In this work, we report a systematic study of the electronic structures, band topology, and intrinsic spin Hall effect (SHE) of the layered MAX carbides Mn+1AlCn (M= Nb, Ta, n=1, 2, 3) and explore the correlation effects on the SHE. The results show that M3AlC2 and M4AlC3 (M= Nb, Ta) share similar Dirac-band-crossing features near the Fermi level (EF) and form nodal lines in the absence of spin-or… ▽ More In this work, we report a systematic study of the electronic structures, band topology, and intrinsic spin Hall effect (SHE) of the layered MAX carbides Mn+1AlCn (M= Nb, Ta, n=1, 2, 3) and explore the correlation effects on the SHE. The results show that M3AlC2 and M4AlC3 (M= Nb, Ta) share similar Dirac-band-crossing features near the Fermi level (EF) and form nodal lines in the absence of spin-orbit coupling (SOC). When the SOC is included, the Dirac band crossings are fully gapped, resulting in nontrivial Z2 topological invariants (1;000) with a pair of surface states on the (001) plane. Remarkably, the multiple gapped Dirac points contribute to locally strong spin Berry curvatures, which lead to large spin Hall conductivities and a giant spin Hall angle up to ~ 60% for Ta3AlC2. Moreover, we also elucidate the impact of Hubbard U correction on SHC. Our findings indicate that Ta3AlC2 might represent an intriguing layered Z2 topological metal with superior charge-to-spin conversion efficiency. △ Less

Submitted 9 August, 2025; originally announced August 2025.

4D-PreNet: A Unified Preprocessing Framework for 4D-STEM Data Analysis

Authors: Mingyu Liu, Zian Mao, Zhu Liu, Haoran Zhang, Jintao Guo, Xiaoya He, Xi Huang, Shufen Chu, Chun Cheng, Jun Ding, Yujun Xie

Abstract: Automated experimentation with real time data analysis in scanning transmission electron microscopy (STEM) often require end-to-end framework. The four-dimensional scanning transmission electron microscopy (4D-STEM) with high-throughput data acquisition has been constrained by the critical bottleneck results from data preprocessing. Pervasive noise, beam center drift, and elliptical distortions du… ▽ More Automated experimentation with real time data analysis in scanning transmission electron microscopy (STEM) often require end-to-end framework. The four-dimensional scanning transmission electron microscopy (4D-STEM) with high-throughput data acquisition has been constrained by the critical bottleneck results from data preprocessing. Pervasive noise, beam center drift, and elliptical distortions during high-throughput acquisition inevitably corrupt diffraction patterns, systematically biasing quantitative measurements. Yet, conventional correction algorithms are often material-specific and fail to provide a robust, generalizable solution. In this work, we present 4D-PreNet, an end-to-end deep-learning pipeline that integrates attention-enhanced U-Net and ResNet architectures to simultaneously perform denoising, center correction, and elliptical distortion calibration. The network is trained on large, simulated datasets encompassing a wide range of noise levels, drift magnitudes, and distortion types, enabling it to generalize effectively to experimental data acquired under varying conditions. Quantitative evaluations demonstrate that our pipeline reduces mean squared error by up to 50% during denoising and achieves sub-pixel center localization in the center detection task, with average errors below 0.04 pixels. The outputs are bench-marked against traditional algorithms, highlighting improvements in both noise suppression and restoration of diffraction patterns, thereby facilitating high-throughput, reliable 4D-STEM real-time analysis for automated characterization. △ Less

Submitted 22 August, 2025; v1 submitted 5 August, 2025; originally announced August 2025.

Comments: The corresponding author does not agree to publish

ACM Class: I.2.10; I.5.1; J.2

Data-driven ANN model for estimating unfrozen water content in the thermo-hydraulic simulation of frozen soils

Authors: Mingpeng Liu, Peizhi Zhuang, Raul Fuentes

Abstract: This study integrates a data-driven model for estimating the unfrozen water content into the thermo-hydraulic coupling simulation of frozen soils. An artificial neural network (ANN) was employed to develop this data-driven model using a dataset from the literature. Thereafter, a numerical algorithm was developed to implement the data-driven model into the thermo-hydraulic simulation. In the numeri… ▽ More This study integrates a data-driven model for estimating the unfrozen water content into the thermo-hydraulic coupling simulation of frozen soils. An artificial neural network (ANN) was employed to develop this data-driven model using a dataset from the literature. Thereafter, a numerical algorithm was developed to implement the data-driven model into the thermo-hydraulic simulation. In the numerical algorithm, the frozen and unfrozen zones are distinguished first according to the freezing temperature, where the unfrozen water at frozen nodes is updated using the ANN model. Subsequently, discretized hydraulic and thermal equations are solved sequentially and iteratively using Newton-Raphson method until the temperature and unfrozen water content satisfy the tolerance simultaneously. Horizontal and vertical freezing experiments are used to verify the reliability of the proposed algorithm. The computed variations in temperature, total water, unfrozen water, and ice content achieve good agreements with measured data. Some key features of frozen soils, such as water migration and ice formation, and the increase in total water content, are reproduced by the developed algorithm. Additionally, the comparison between the ANN model and existing empirical equations for determining unfrozen water content demonstrates that the ANN model offers a better performance. △ Less

Submitted 3 August, 2025; originally announced August 2025.

Pairing without $γ$-Pocket in the La$_3$Ni$_2$O$_7$ Thin Film

Authors: Zhi-Yan Shao, Chen Lu, Min Liu, Yu-Bo Liu, Zhiming Pan, Congjun Wu, Fan Yang

Abstract: The recent discovery of high-temperature superconductivity (HTSC) in the La$_3$Ni$_2$O$_7$ ultrathin film at ambient pressure has aroused great research interest. The $γ$-pocket formed by the bonding $d_{z^2}$ band, which was previously proposed to be crucial in the pairing mechanism of pressurized bulk La$_3$Ni$_2$O$_7$, is reported to be either present or absent here by different experimental gr… ▽ More The recent discovery of high-temperature superconductivity (HTSC) in the La$_3$Ni$_2$O$_7$ ultrathin film at ambient pressure has aroused great research interest. The $γ$-pocket formed by the bonding $d_{z^2}$ band, which was previously proposed to be crucial in the pairing mechanism of pressurized bulk La$_3$Ni$_2$O$_7$, is reported to be either present or absent here by different experimental groups, giving rise to the problem: what is the pairing mechanism and pairing nature without the $γ$-pocket? Here, we start from a band structure obtained via density-functional-theoretical calculation, which exhibits no $γ$-pocket. Then, equipped with electron interactions, we study the pairing nature via combined weak- and strong- coupling approaches, which provide consistent results. In the weak-coupling study, the nesting between the $α$- and $β$- pockets leads to an $s^\pm$-wave pairing in which the gap signs on the two pockets are opposite, as provided by our random-phase-approximation based calculations. In real-space, the pairing pattern is dominated by the interlayer pairing of the $d_{x^2-y^2}$ orbital. In the strong-coupling study, as the $d_{z^2}$ orbitals are nearly half-filled and hence localized, the $d_{x^2-y^2}$ orbitals carry the HTSC. Driven by the interlayer superexchange transferred from the $d_{z^2}$ orbital through the Hund's rule coupling, the $d_{x^2-y^2}$ orbital electrons form interlayer $s$-wave pairing, as suggested by our slave-boson-mean-field study on the related two-orbital $t$-$J$ model. Projected onto the Fermi surface, this pairing just gives the $s^\pm$-wave pattern consistent with that obtained in the weak-coupling study. Our result is consistent with that obtained in recent scanning tunneling microscopy experiment. △ Less

Submitted 27 July, 2025; originally announced July 2025.

Direct observation of locally modified excitonic effect within a moiré unit cell in twisted bilayer graphene

Authors: Ming Liu, Ryosuke Senga, Masanori Koshino, Yung-Chang Lin, Kazu Suenaga

Abstract: Bilayer graphene, forming moiré superlattices, possesses distinct electronic and optical properties derived from the hybridization of energy band and the emergence of van Hove singularities depending on its twist angle. Extensive research has been conducted on the global characteristics of moiré superlattice induced by long-range periodicity. However, limited attention has been given to the local… ▽ More Bilayer graphene, forming moiré superlattices, possesses distinct electronic and optical properties derived from the hybridization of energy band and the emergence of van Hove singularities depending on its twist angle. Extensive research has been conducted on the global characteristics of moiré superlattice induced by long-range periodicity. However, limited attention has been given to the local properties within a moiré unit cell, which undoubtedly differ due to the variations in three-dimensional atomic arrangement. Here we demonstrate the highly localized excitations of carbon 1s electrons to unoccupied van Hove singularities in a twisted bilayer graphene using an electron energy loss spectroscopy based on a monochromated transmission electron microscope. The core-level excitations associated with the van Hove singularities show a systematic twist angle dependence which is analogous to the optical excitations. Furthermore, local variations in those core-level van Hove singularity peaks within a moiré unit cell have been corroborated for the first time, which can originate from core-exciton lifetimes and band modifications influenced by the local stacking geometry. △ Less

Submitted 7 July, 2025; originally announced July 2025.

Comments: 33 pages with 4 figures for maintext and 5 pages with 3 figures for supporting information

Journal ref: ACS Nano 17 (2023) 18433-18440

Midveins regulate the shape formation of drying leaves

Authors: Kexin Guo, Yafei Zhang, Massimo Paradiso, Yuchen Long, K. Jimmy Hsia, Mingchao Liu

Abstract: Dried leaves in nature often exhibit curled and crumpled morphologies, typically attributed to internal strain gradients that produce dome-like shapes. However, the origin of these strain gradients remains poorly understood. Although leaf veins--particularly the midvein--have been suggested to influence shape formation, their mechanical role has not been systematically investigated. Here, we demon… ▽ More Dried leaves in nature often exhibit curled and crumpled morphologies, typically attributed to internal strain gradients that produce dome-like shapes. However, the origin of these strain gradients remains poorly understood. Although leaf veins--particularly the midvein--have been suggested to influence shape formation, their mechanical role has not been systematically investigated. Here, we demonstrate that mechanical constraints imposed by the midvein play a crucial role in generating the diverse morphologies that emerge during leaf drying. Combining numerical simulations and theoretical analysis, we show that a uniformly shrinking leaf lamina constrained by a non-shrinking midvein gives rise to two distinct types of configurations: curling-dominated and folding-dominated morphologies. In the curling-dominated regime, both S-curled and C-curled shapes emerge, with C-curled configurations more commonly observed due to their lower elastic energy. In contrast, the folding-dominated regime features folding accompanied by edge waviness. Theoretical modeling reveals a linear relationship between midvein curvature and mismatch strain, consistent with simulation results. Moreover, we find that the morphological outcome is governed by the ratio of bending stiffnesses between the lamina and the midvein. We construct a comprehensive phase diagram for the transitions between different configurations. These findings provide a mechanical framework for understanding shape formation in drying leaves, offering new insights into natural morphing processes and informing the design of bio-inspired morphable structures. △ Less

Submitted 2 July, 2025; originally announced July 2025.

Comments: 19 pages, 9 figures

Diverse polymorphs and phase transitions in van der Waals In$_2$Se$_3$

Authors: Mingfeng Liu, Jiantao Wang, Peitao Liu, Qiang Wang, Zhibo Liu, Yan Sun, Xing-Qiu Chen

Abstract: Van der Waals In$_2$Se$_3$ has garnered significant attention due to its unique properties and wide applications associated with its rich polymorphs and polymorphic phase transitions. Despite extensive studies, the vast complex polymorphic phase space remains largely unexplored, and the underlying microscopic mechanism for their phase transformations remains elusive. Here, we develop a highly accu… ▽ More Van der Waals In$_2$Se$_3$ has garnered significant attention due to its unique properties and wide applications associated with its rich polymorphs and polymorphic phase transitions. Despite extensive studies, the vast complex polymorphic phase space remains largely unexplored, and the underlying microscopic mechanism for their phase transformations remains elusive. Here, we develop a highly accurate, efficient, and reliable machine-learning potential (MLP), which not only facilitates accurate exploration of the intricate potential energy surface (PES), but also enables us to conduct large-scale molecular dynamics (MD) simulations with first-principles accuracy. We identify the accurate structure of the $β''$ polymorph and uncover several previously unreported $β'$ polymorph variants exhibiting dynamic stability and competing energies, which are elucidated by characteristic flat imaginary phonon bands and the distinctive Mexican-hat-like PES in the $β$ polymorph. Through the MLP-accelerated MD simulations, we directly observe the polymorphic phase transformations among the $α$, $β$, $β'$, and $β''$ polymorphs under varying temperature and pressure conditions, and build for the first time an ab initio temperature-pressure phase diagram, showing good agreement with experiments. Furthermore, our MD simulations reveal a novel strain-induced reversible phase transition between the $β'$ and $β''$ polymorphs. This work not only unveils diverse polymorphs in van der Waals In$_2$Se$_3$, but also provides crucial atomic insights into their phase transitions, opening new avenues for the design of novel functional electronic devices. △ Less

Submitted 26 June, 2025; originally announced June 2025.

Comments: 32 pages, 20 figures (including Supplementary Information)

Pseudomagnetotransport in Strained Graphene

Authors: Alina Mreńca-Kolasińska, Christophe De Beule, Jia-Tong Shi, Aitor Garcia-Ruiz, Denis Kochan, Klaus Richter, Ming-Hao Liu

Abstract: In graphene, long-wavelength deformations that result in elastic shear strain couple to the low-energy Dirac electrons as pseudogauge fields. Using a scalable tight-binding model, we consider analogs to magnetotransport in mesoscopic strained graphene devices with nearly uniform pseudomagnetic fields. In particular, we consider transverse pseudomagnetic focusing in a bent graphene ribbon and show… ▽ More In graphene, long-wavelength deformations that result in elastic shear strain couple to the low-energy Dirac electrons as pseudogauge fields. Using a scalable tight-binding model, we consider analogs to magnetotransport in mesoscopic strained graphene devices with nearly uniform pseudomagnetic fields. In particular, we consider transverse pseudomagnetic focusing in a bent graphene ribbon and show that a focused valley-polarized current can be generated with characteristic conductance oscillations. Importantly, our scaling method allows for quantum transport calculations with realistic device geometries, and leaves the Dirac physics and pseudogauge fields invariant as long as the atomic displacements vary slowly with respect to the scaled lattice. Our results show that pseudomagnetotransport is a promising new route for graphene straintronics, and our scaling method provides a new framework for the modeling, design, and interpretation of straintronics experiments and applications. △ Less

Submitted 27 May, 2025; originally announced May 2025.

Comments: 7 pages + 9 pages supplementary file, 12 figures

Polaritonic Quantum Matter

Authors: D. N. Basov, A. Asenjo-Garcia, P. J. Schuck, X. -Y. Zhu, A. Rubio, A. Cavalleri, M. Delor, M. M. Fogler, Mengkun Liu

Abstract: Polaritons are quantum mechanical superpositions of photon states with elementary excitations in molecules and solids. The light-matter admixture causes a characteristic frequency-momentum dispersion shared by all polaritons irrespective of the microscopic nature of material excitations that could entail charge, spin, lattice or orbital effects. Polaritons retain the strong nonlinearities of their… ▽ More Polaritons are quantum mechanical superpositions of photon states with elementary excitations in molecules and solids. The light-matter admixture causes a characteristic frequency-momentum dispersion shared by all polaritons irrespective of the microscopic nature of material excitations that could entail charge, spin, lattice or orbital effects. Polaritons retain the strong nonlinearities of their matter component and simultaneously inherit ray-like propagation of light. Polaritons prompt new properties, enable new opportunities for spectroscopy/imaging, empower quantum simulations and give rise to new forms of synthetic quantum matter. Here, we review the emergent effects rooted in polaritonic quasiparticles in a wide variety of their physical implementations. We present a broad portfolio of the physical platforms and phenomena of what we term polaritonic quantum matter. We discuss the unifying aspects of polaritons across different platforms and physical implementations and focus on recent developments in: polaritonic imaging, cavity electrodynamics and cavity materials engineering, topology and nonlinearities, as well as quantum polaritonics. △ Less

Submitted 8 May, 2025; originally announced May 2025.

Journal ref: Nanophotonics, 2025

Flexible Perovskite/Silicon Monolithic Tandem Solar Cells Approaching 30% Efficiency

Authors: Yinqing Sun, Faming Li, Hao Zhang, Wenzhu Liu, Zenghui Wang, Lin Mao, Qian Li, Youlin He, Tian Yang, Xianggang Sun, Yicheng Qian, Yinyi Ma, Liping Zhang, Junlin Du, Jianhua Shi, Guangyuan Wang, Anjun Han, Na Wang, Fanying Meng, Zhengxin Liu, Mingzhen Liu

Abstract: Thanks to their excellent properties of low cost, lightweight, portability, and conformity, flexible perovskite-based tandem solar cells show great potentials for energy harvesting applications, with flexible perovskite/c-silicon tandem solar cells particularly promising for achieving high efficiency. However, performance of flexible perovskite/c-silicon monolithic tandem solar cells still greatly… ▽ More Thanks to their excellent properties of low cost, lightweight, portability, and conformity, flexible perovskite-based tandem solar cells show great potentials for energy harvesting applications, with flexible perovskite/c-silicon tandem solar cells particularly promising for achieving high efficiency. However, performance of flexible perovskite/c-silicon monolithic tandem solar cells still greatly lags, due to challenges in simultaneously achieving both efficient photocarrier transport and reliable mitigation of residual stress. Here, we reveal the critical role of perovskite phase homogeneity, for achieving high-efficient and mechanical-stable flexible perovskite/c-silicon heterojunction monolithic tandem solar cells (PSTs) with textured surface. Through ensuring high phase homogeneity, which promotes charge transfer across all facets of the pyramid on the textured substrates and releases the residual stress at the perovskite/c-silicon interface, we demonstrate flexible PSTs with a bending curvature of 0.44 cm-1, and a certified power conversion efficiency of 29.88% (1.04 cm2 aperture area), surpassing all other types of flexible perovskite-based photovoltaic devices. Our results can lead to broad applications and commercialization of flexible perovskite/c-silicon tandem photovoltaics. △ Less

Submitted 29 April, 2025; originally announced April 2025.

Journal ref: Nature Communications 2025

Engineering Graphene Nanoribbons via Periodically Embedding Oxygen Atoms

Authors: Yan Zhao, Li-Xia Kang, Yi-Jun Wang, Yi Wu, Guang-Yan Xing, Shi-Wen Li, Jinliang Pan, Nie-Wei Wang, Yin-Ti Ren, Ying Wang, Ya-Cheng Zhu, Xing-Qiang Shi, Mengxi Liu, Xiaohui Qiu, Pei-Nian Liu, Deng-Yuan Li

Abstract: Heteroatom doping is an important method for engineering graphene nanoribbons (GNRs) because of its ability to modify electronic properties by introducing extra electrons or vacancies. However, precisely integrating oxygen atoms into the lattice of GNRs is unexplored, and the resulting electronic properties remain elusive. Here, we achieve the precise embedding of oxygen atoms into the lattice of… ▽ More Heteroatom doping is an important method for engineering graphene nanoribbons (GNRs) because of its ability to modify electronic properties by introducing extra electrons or vacancies. However, precisely integrating oxygen atoms into the lattice of GNRs is unexplored, and the resulting electronic properties remain elusive. Here, we achieve the precise embedding of oxygen atoms into the lattice of GNRs via in situ formation of pyrans, synthesizing two types of oxygen-doped GNRs (O-doped chevron-GNR and O-doped chiral (2,1)-GNR). Using scanning tunneling microscopy, non-contact atomic force microscopy, and density functional theory calculations, the atomic structures and electronic properties of O-doped GNRs are determined, demonstrating that both GNRs are direct bandgap semiconductors with different sensitivities to oxygen dopants. Oxygen dopants have a minor impact on the bandgap of chevron-GNR but a significant effect on the bandgap of chiral (2,1)-GNR, which is attributed to the difference in density of states near the Fermi level between substituted intrinsic carbon atoms and their pristine counterparts. Compared with the pristine chiral (2,1)-GNR, the band structure of O-doped chiral (2,1)-GNR exhibits unexpected band edges transition, which is ascribed to sp2-hybridized oxygen atoms which introduces additional electrons to the conduction band of chiral (2,1)-GNR, leading to the upward shift of Fermi surface. △ Less

Submitted 25 April, 2025; originally announced April 2025.

Magnetically disordered ground state in the triangular-lattice antiferromagnets Rb$_3$Yb(VO$_4$)$_2$ and Cs$_3$Yb(VO$_4$)$_2$

Authors: Zhen Ma, Yingqi Chen, Zhongtuo Fu, Shuaiwei Li, Xin-An Tong, Hong Du, Jan Peter Embs, Shuhan Zheng, Yongjun Zhang, Meifeng Liu, Ruidan Zhong, Jun-Ming Liu, Jinsheng Wen

Abstract: Quantum spin liquids~(QSLs) represent a unique quantum disordered state of matter that hosts long-range quantum entanglement and fractional excitations. However, structural disorder resulting from site mixing between different types of ions usually arises in real QSL candidates, which is considered as an obstacle to gain the insight into the intrinsic physics. Here, we have synthesized two new rar… ▽ More Quantum spin liquids~(QSLs) represent a unique quantum disordered state of matter that hosts long-range quantum entanglement and fractional excitations. However, structural disorder resulting from site mixing between different types of ions usually arises in real QSL candidates, which is considered as an obstacle to gain the insight into the intrinsic physics. Here, we have synthesized two new rare-earth compounds Rb$_3$Yb(VO$_4$)$_2$ and Cs$_3$Yb(VO$_4$)$_2$. X-ray diffractions reveal a perfect triangular-lattice structure with no detectable disorder. Magnetic susceptibility measurements do not capture any phase transition or spin freezing down to 1.8~K. A fit to low-temperature data indicates dominant antiferromagnetic interactions with the Curie-Weiss temperature of -1.40~K and -0.43~K for Rb$_3$Yb(VO$_4$)$_2$ and Cs$_3$Yb(VO$_4$)$_2$, respectively. Specific heat results show no sign of long-range magnetic order down to $\sim$0.1~K either, but only a Schottky anomaly that is continuously mediated by the external magnetic fields. Additionally, inelastic neutron scattering is employed to detect low-energy spin excitations in Rb$_3$Yb(VO$_4$)$_2$. The absence of magnetic excitation signals as well as static magnetic order down to 97~mK aligns with the results from magnetic susceptibility and specific heat. Collectively, these findings point to a quantum disordered ground state with persistent spin dynamics, reminiscent of QSL behaviors. Our work provides a promising platform for further exploration of quantum magnetism in this new disorder-free system. △ Less

Submitted 24 April, 2025; originally announced April 2025.

Comments: 11 pages, 5 figures

Journal ref: Phys. Rev. B 111, 155141 (2025)

Bolometric Superconducting Optical Nanoscopy (BOSON)

Authors: Ran Jing, Boyi Zhou, Dingchen Kang, Wenjun Zheng, Zijian Zhou, Heng Wang, Xinzhong Chen, Juntao Yao, Bing Cheng, Ji-Hoon Park, Lukas Wehmeier, Zhenbing Dai, Shoujing Chen, Christopher D. Prainito, G. L. Carr, Ilya Charaev, Denis Bandurin, Genda Gu, Qiang Li, Karl. K. Berggren, D. N. Basov, Xu Du, Mengkun Liu

Abstract: Superconducting transition-edge sensors are renowned for their extraordinary photon sensitivity and energy resolution, finding applications spanning quantum information, astronomy, and nanophotonics. Here, we report the development of BOlometric Superconducting Optical Nanoscopy (BOSON), a novel platform that integrates bolometric detection at the superconducting transition edges with near-field o… ▽ More Superconducting transition-edge sensors are renowned for their extraordinary photon sensitivity and energy resolution, finding applications spanning quantum information, astronomy, and nanophotonics. Here, we report the development of BOlometric Superconducting Optical Nanoscopy (BOSON), a novel platform that integrates bolometric detection at the superconducting transition edges with near-field optical techniques. BOSON enables the mapping of photoinduced changes in superconductivity with unprecedented spatial resolution and photon sensitivity. By incorporating BOSON with low-dimensional materials, we achieved polariton imaging at nanowatt excitation levels--at least four orders of magnitude lower than the power typically required in prior near-field nanoscopy experiments. Our findings highlight the potential for BOSON to advance scanning probe based optical platforms to enable the detection of photons, polaritons, and Cooper pair dynamics at the nanoscale. This paves the way for quantum sensing applications using single-polariton detection and can offer deeper insights into quasiparticle dynamics. △ Less

Submitted 20 April, 2025; originally announced April 2025.

Comments: 13 pages, 4 figures

Increasing Downshifting Luminescence Intensity Through an Extended Active Layer

Authors: Miao Liu, Jinyang Liang, Fiorenzo Vetrone

Abstract: The near-infrared (NIR) emission of rare-earth doped nanoparticles (RENPs), known as downshifting luminescence, has been extensively investigated in diverse applications from information technology to biomedicine. In promoting brightness and enriching the functionalities of the downshifting luminescence of RENPs, numerous studies have exploited inert shell to protect rare-earth dopants from surfac… ▽ More The near-infrared (NIR) emission of rare-earth doped nanoparticles (RENPs), known as downshifting luminescence, has been extensively investigated in diverse applications from information technology to biomedicine. In promoting brightness and enriching the functionalities of the downshifting luminescence of RENPs, numerous studies have exploited inert shell to protect rare-earth dopants from surface quenchers. However, internal concentration quenching remains an unsolved puzzle when using higher dopant concentrations of rare-earth ions in an attempt to obtain brighter emission. Following a plethora of research involving core-shell structures, the interface has shown to be controllable, ranging from a well-defined, abrupt boundary to an obscure one with cation intermixing. By utilizing this inter-mixed core-shell property for the first time, we design a new architecture to create a homogeneous double-layer core-shell interface to extend the active layer, allowing more luminescent centers without severe concentration quenching. By systematically deploying the crystallinity of the starting core, shell growth dynamics, and dopant concentrations, the downshifting luminescence intensity of new archictecture achieves a 12-fold enhancement surpassing the traditional core-shell structure. These results provide deeper insight into the potential benefits of the intermixed core-shell structure, offering an effective approach to tackling the internal concentration quenching effect for highly boosted NIR optical performance. △ Less

Submitted 17 April, 2025; originally announced April 2025.

A tutorial on simulating nonlinear behaviors of flexible structures with the discrete differential geometry (DDG) method

Authors: Weicheng Huang, Zhuonan Hao, Jiahao Li, Dezhong Tong, Kexin Guo, Yingchao Zhang, Huajian Gao, K. Jimmy Hsia, Mingchao Liu

Abstract: Flexible elastic structures, such as beams, rods, ribbons, plates, and shells, exhibit complex nonlinear dynamical behaviors that are central to a wide range of engineering and scientific applications, including soft robotics, deployable structures, and biomedical devices. While various numerical methods have been developed to simulate these behaviors, many conventional approaches struggle to simu… ▽ More Flexible elastic structures, such as beams, rods, ribbons, plates, and shells, exhibit complex nonlinear dynamical behaviors that are central to a wide range of engineering and scientific applications, including soft robotics, deployable structures, and biomedical devices. While various numerical methods have been developed to simulate these behaviors, many conventional approaches struggle to simultaneously capture geometric and material nonlinearities, as well as nonlinear external interactions, particularly in highly deformable and dynamically evolving systems. The Discrete Differential Geometry (DDG) method has emerged as a robust and efficient numerical framework that intrinsically preserves geometric properties, accommodates material nonlinearity, and accurately models interactions with external environments and fields. By directly discretizing geometric and mechanical quantities, DDG provides an accurate, stable, and efficient approach to modeling flexible structures, addressing key limitations of traditional numerical methods. This tutorial provides a systematic introduction to the DDG method for simulating nonlinear behaviors in flexible structures. It covers DDG theory, simulation frameworks, and MATLAB implementation, with examples spanning dynamic systems, geometric and material nonlinearities, and external interactions like magnetics and fluids, culminating in practical insights and future directions. By offering a comprehensive and practical guide, together with open-source MATLAB code, this tutorial aims to facilitate the broader adoption of DDG-based numerical tools among researchers and engineers in computational mechanics, applied mathematics, and structural design. △ Less

Submitted 15 April, 2025; originally announced April 2025.

Comments: 87 pages

Photocurrent Nanoscopy of Quantum Hall Bulk

Authors: Ran Jing, Boyi Zhou, Jiacheng Sun, Shoujing Chen, Wenjun Zheng, Zijian Zhou, Heng Wang, Lukas Wehmeier, Bing Cheng, Michael Dapolito, Yinan Dong, Zengyi Du, G. L. Carr, Xu Du, D. N. Basov, Qiang Li, Mengkun Liu

Abstract: Understanding nanoscale electronic and thermal transport of two-dimensional (2D) electron systems in the quantum Hall regime, particularly in the bulk insulating state, poses considerable challenges. One of the primary difficulties arises from the presence of chiral edge channels, whose transport behavior obscures the investigation of the insulating bulk. Using near-field (NF) optical and photocur… ▽ More Understanding nanoscale electronic and thermal transport of two-dimensional (2D) electron systems in the quantum Hall regime, particularly in the bulk insulating state, poses considerable challenges. One of the primary difficulties arises from the presence of chiral edge channels, whose transport behavior obscures the investigation of the insulating bulk. Using near-field (NF) optical and photocurrent (PC) nanoscopy, we probe real-space variations of the optical and thermal dynamics of graphene in the quantum Hall regime without relying on complex sample or electrode geometries. Near the charge neutrality point (CNP), we detect strong optical and photothermal signals from resonant inter-Landau level (LL) magnetoexciton excitations between the 0th and +-1st LLs, which gradually weaken with increasing doping due to Pauli blocking. Interestingly, at higher doping levels and full integer LL fillings, photothermal signals reappear across the entire sample over a ~10-micrometer scale, indicating unexpectedly long cooling lengths and nonlocal photothermal heating through the insulating bulk. This observation suggests thermal conductivity persists for the localized states even as electronic transport is suppressed - a clear violation of the Wiedemann-Franz (WF) law. Our experiments provide novel insights into nanoscale thermal and electronic transport in incompressible 2D gases, highlighting the roles of magnetoexcitons and chiral edge states in the thermo-optoelectric dynamics of Dirac quantum Hall state. △ Less

Submitted 13 April, 2025; originally announced April 2025.

Comments: 18 pages, 4 figures

Atomic structure of the PL5 defect in silicon carbide revealed by single-spin spectroscopy and oxygen implantation

Authors: Yu Chen, Qi Zhang, Mingzhe Liu, Junda Wu, Jinpeng Liu, Xin Zhao, Jingyang Zhou, Pei Yu, Shaochun Lin, Yuanhong Teng, Wancheng Yu, Ya Wang, Changkui Duan, Fazhan Shi

Abstract: PL5 and PL6 centers in 4H-SiC are promising for quantum applications due to their superior charge stability and optically detected magnetic resonance (ODMR) properties at room temperature. However, their atomic structures remain unresolved, with ongoing controversy regarding their potential association with stacking faults. Previous measurements relying on spin ensemble detection were insufficient… ▽ More PL5 and PL6 centers in 4H-SiC are promising for quantum applications due to their superior charge stability and optically detected magnetic resonance (ODMR) properties at room temperature. However, their atomic structures remain unresolved, with ongoing controversy regarding their potential association with stacking faults. Previous measurements relying on spin ensemble detection were insufficient to draw definitive conclusions. In this work, we conduct correlative imaging of stacking faults and PL5/PL6 at the single-defect level, definitively ruling out any spatial correlation and demonstrating that these centers are not associated with stacking faults. Furthermore, we find that substituting oxygen for nitrogen in ion implantation enhances the yields of PL5 and PL6 by more than $11$-fold and $23$-fold, respectively. Single-spin ODMR spectroscopy of PL5 reveals six distinct orientations, determines the transverse zero-field splitting parameter $E$, and characterizes the hyperfine coupling. Combined with our ab initio calculations, these results provide compelling evidence for the assignment of PL5 as an OV($kh$) defect, consisting of an oxygen atom occupying the C($k$) site as the nearest neighbor to a Si($h$) vacancy. The structural analysis together with the demonstrated defect yield enhancement lays the foundation for fabricating high-sensitivity, high-contrast ensemble quantum sensors in two and three dimensions. △ Less

Submitted 18 December, 2025; v1 submitted 10 April, 2025; originally announced April 2025.

Comments: 7 pages, 6 figures

Localization of deformation in the central hub of hub-and-spoke kirigami

Authors: Jason Barckicke, Lucie Domino, Qun Zhang, Mingchao Liu, Dominic Vella

Abstract: A recent approach to the design of flexible electronic devices consists of cutting a two-dimensional sheet to form a central hub connected to several tapered `spokes', resembling the hub-and-spoke of a bicycle wheel. When radially compressed, the resulting cut sheet buckles out-of-plane forming a structure whose three-dimensional shape can be chosen by designing the tapering of the spokes. While t… ▽ More A recent approach to the design of flexible electronic devices consists of cutting a two-dimensional sheet to form a central hub connected to several tapered `spokes', resembling the hub-and-spoke of a bicycle wheel. When radially compressed, the resulting cut sheet buckles out-of-plane forming a structure whose three-dimensional shape can be chosen by designing the tapering of the spokes. While the deformation of the spokes in this `hub-and-spoke' kirigami are approximately cylindrical (i.e.~zero Gaussian curvature and hence small elastic strain), this is not the case in the central hub. The central hub is deformed radially because of continuity with the spokes but, because of its own circular symmetry, it must develop Gaussian curvature, and hence strain. In this article we quantify this strain, focussing in particular on its magnitude and its location. We find that the strain is localized in a boundary layer near the edge of the hub region, whose size is controlled by the moment applied on it by the deformed spokes. We discuss the implications of our results for avoiding material failure in flexible-electronic devices. △ Less

Submitted 9 April, 2025; originally announced April 2025.

Roadmap for Photonics with 2D Materials

Authors: F. Javier García de Abajo, D. N. Basov, Frank H. L. Koppens, Lorenzo Orsini, Matteo Ceccanti, Sebastián Castilla, Lorenzo Cavicchi, Marco Polini, P. A. D. Gonçalves, A. T. Costa, N. M. R. Peres, N. Asger Mortensen, Sathwik Bharadwaj, Zubin Jacob, P. J. Schuck, A. N. Pasupathy, Milan Delor, M. K. Liu, Aitor Mugarza, Pablo Merino, Marc G. Cuxart, Emigdio Chávez-Angel, Martin Svec, Luiz H. G. Tizei, Florian Dirnberger , et al. (123 additional authors not shown)

Abstract: Triggered by the development of exfoliation and the identification of a wide range of extraordinary physical properties in self-standing films consisting of one or few atomic layers, two-dimensional (2D) materials such as graphene, transition metal dichalcogenides (TMDs), and other van der Waals (vdW) crystals currently constitute a wide research field protruding in multiple directions in combinat… ▽ More Triggered by the development of exfoliation and the identification of a wide range of extraordinary physical properties in self-standing films consisting of one or few atomic layers, two-dimensional (2D) materials such as graphene, transition metal dichalcogenides (TMDs), and other van der Waals (vdW) crystals currently constitute a wide research field protruding in multiple directions in combination with layer stacking and twisting, nanofabrication, surface-science methods, and integration into nanostructured environments. Photonics encompasses a multidisciplinary collection of those directions, where 2D materials contribute with polaritons of unique characteristics such as strong spatial confinement, large optical-field enhancement, long lifetimes, high sensitivity to external stimuli (e.g., electric and magnetic fields, heating, and strain), a broad spectral range from the far infrared to the ultraviolet, and hybridization with spin and momentum textures of electronic band structures. The explosion of photonics with 2D materials as a vibrant research area is producing breakthroughs, including the discovery and design of new materials and metasurfaces with unprecedented properties as well as applications in integrated photonics, light emission, optical sensing, and exciting prospects for applications in quantum information, and nanoscale thermal transport. This Roadmap summarizes the state of the art in the field, identifies challenges and opportunities, and discusses future goals and how to meet them through a wide collection of topical sections prepared by leading practitioners. △ Less

Submitted 14 April, 2025; v1 submitted 6 April, 2025; originally announced April 2025.

Comments: 199 pages, 42 figures, 1154 references

Journal ref: ACS Photonics 12, 3961 (2025)

Spin-to-orbital angular momentum conversion in non-Hermitian photonic graphene

Authors: Zhaoyang Zhang, Pavel Kokhanchik, Zhenzhi Liu, Yutong Shen, Fu Liu, Maochang Liu, Yanpeng Zhang, Min Xiao, Guillaume Malpuech, Dmitry Solnyshkov

Abstract: Optical beams with orbital angular momentum (OAM) have numerous potential applications, but the means used for their generation often lack crucial on-demand control. In this work, we present a mechanism of converting spin angular momentum (SAM) to OAM in a non-structured beam. The conversion occurs through spin-orbit coupling in a reconfigurable photonic honeycomb lattice with staggering implement… ▽ More Optical beams with orbital angular momentum (OAM) have numerous potential applications, but the means used for their generation often lack crucial on-demand control. In this work, we present a mechanism of converting spin angular momentum (SAM) to OAM in a non-structured beam. The conversion occurs through spin-orbit coupling in a reconfigurable photonic honeycomb lattice with staggering implemented by electromagnetically-induced transparency in an atomic vapor cell. The spin-orbit coupling allows to outcouple the OAM signal from a particular band in a given valley determined by the chirality of light or the lattice staggering, providing a non-zero Berry curvature for generating OAM. The dependence of the output OAM on the chirality of the input beam is the first control knob. The staggering works as a second control knob, flipping the sign of OAM for the fixed chirality. The demonstrated conversion between SAM and OAM is important for optical communications. Our results can be extended to other implementations of paraxial photonic graphene. △ Less

Submitted 4 April, 2025; originally announced April 2025.

Accelerating and enhancing thermodynamic simulations of electrochemical interfaces

Authors: Xiaochen Du, Mengren Liu, Jiayu Peng, Hoje Chun, Alexander Hoffman, Bilge Yildiz, Lin Li, Martin Z. Bazant, Rafael Gómez-Bombarelli

Abstract: Electrochemical interfaces are crucial in catalysis, energy storage, and corrosion, where their stability and reactivity depend on complex interactions between the electrode, adsorbates, and electrolyte. Predicting stable surface structures remains challenging, as traditional surface Pourbaix diagrams tend to either rely on expert knowledge or costly $\textit{ab initio}$ sampling, and neglect ther… ▽ More Electrochemical interfaces are crucial in catalysis, energy storage, and corrosion, where their stability and reactivity depend on complex interactions between the electrode, adsorbates, and electrolyte. Predicting stable surface structures remains challenging, as traditional surface Pourbaix diagrams tend to either rely on expert knowledge or costly $\textit{ab initio}$ sampling, and neglect thermodynamic equilibration with the environment. Machine learning (ML) potentials can accelerate static modeling but often overlook dynamic surface transformations. Here, we extend the Virtual Surface Site Relaxation-Monte Carlo (VSSR-MC) method to autonomously sample surface reconstructions modeled under aqueous electrochemical conditions. Through fine-tuning foundational ML force fields, we accurately and efficiently predict surface energetics, recovering known Pt(111) phases and revealing new LaMnO$_\mathrm{3}$(001) surface reconstructions. By explicitly accounting for bulk-electrolyte equilibria, our framework enhances electrochemical stability predictions, offering a scalable approach to understanding and designing materials for electrochemical applications. △ Less

Submitted 22 March, 2025; originally announced March 2025.

Comments: 19 pages main text, 5 figures, supplementary information (SI) in ancillary files

Towards Identifying the PL6 Center in SiC: From First-Principles Screening to Hyperfine Validation of Competing Defect Candidates

Authors: Xin Zhao, Mingzhe Liu, Yu Chen, Qi Zhang, Chang-Kui Duan

Abstract: The PL6 color center in 4H-SiC, known for its excellent ambient-temperature spin and optical properties, has an unresolved microscopic origin. In this first-principles study, we systematically investigate potential structures to clarify its nature. We first rigorously examine the DV-antisite hypothesis (a divacancy paired with a carbon antisite, $\mathrm{C_{Si}}$), analyzing the energetic, electro… ▽ More The PL6 color center in 4H-SiC, known for its excellent ambient-temperature spin and optical properties, has an unresolved microscopic origin. In this first-principles study, we systematically investigate potential structures to clarify its nature. We first rigorously examine the DV-antisite hypothesis (a divacancy paired with a carbon antisite, $\mathrm{C_{Si}}$), analyzing the energetic, electronic, and spin properties of various $V_\mathrm{Si}V_\mathrm{C}+\mathrm{C_{Si}}$ configurations. Two $\mathrm{C_{3v}}$-symmetric $\mathrm{kk+C_{Si}}$ complexes emerge as strong candidates within this framework. Subsequently, a critical comparison of hyperfine interaction signatures is performed between these candidates, the alternative OV model [specifically OV(hh) and OV(kk), an oxygen replacing C together with a Si vacancy], and experimental data. This analysis demonstrates that the OV(hh) structure more accurately reproduces PL6's hyperfine features. Furthermore, re-evaluation of the proposed OV(hk) model for the related PL5 center reveals zero-field splitting parameter $E$ inconsistencies with experimental results, suggesting that PL5 and PL6 may have distinct origins. These findings provide crucial theoretical insights and motivate targeted experimental validation for these quantum defects. △ Less

Submitted 2 August, 2025; v1 submitted 18 March, 2025; originally announced March 2025.

Real-time simulation enabled navigation control of magnetic soft continuum robots in confined lumens

Authors: Dezhong Tong, Zhuonan Hao, Jiyu Li, Boxi Sun, Mingchao Liu, Liu Wang, Weicheng Huang

Abstract: Magnetic soft continuum robots (MSCRs) have emerged as a promising technology for minimally invasive interventions, offering enhanced dexterity and remote-controlled navigation in confined lumens. Unlike conventional guidewires with pre-shaped tips, MSCRs feature a magnetic tip that actively bends under applied magnetic fields. Despite extensive studies in modeling and simulation, achieving real-t… ▽ More Magnetic soft continuum robots (MSCRs) have emerged as a promising technology for minimally invasive interventions, offering enhanced dexterity and remote-controlled navigation in confined lumens. Unlike conventional guidewires with pre-shaped tips, MSCRs feature a magnetic tip that actively bends under applied magnetic fields. Despite extensive studies in modeling and simulation, achieving real-time navigation control of MSCRs in confined lumens remains a significant challenge. The primary reasons are due to robot-lumen contact interactions and computational limitations in modeling MSCR nonlinear behavior under magnetic actuation. Existing approaches, such as Finite Element Method (FEM) simulations and energy-minimization techniques, suffer from high computational costs and oversimplified contact interactions, making them impractical for real-world applications. In this work, we develop a real-time simulation and navigation control framework that integrates hard-magnetic elastic rod theory, formulated within the Discrete Differential Geometry (DDG) framework, with an order-reduced contact handling strategy. Our approach captures large deformations and complex interactions while maintaining computational efficiency. Next, the navigation control problem is formulated as an inverse design task, where optimal magnetic fields are computed in real time by minimizing the constrained forces and enhancing navigation accuracy. We validate the proposed framework through comprehensive numerical simulations and experimental studies, demonstrating its robustness, efficiency, and accuracy. The results show that our method significantly reduces computational costs while maintaining high-fidelity modeling, making it feasible for real-time deployment in clinical settings. △ Less

Submitted 11 March, 2025; originally announced March 2025.

Comments: 22 pages, 12 figures

Continuously varying critical exponents in an exactly solvable long-range cluster XY mode

Authors: Tian-Cheng Yi, Chengxiang Ding, Maoxin Liu, Liangsheng Li, Wen-Long You

Abstract: We investigate a generalized antiferromagnetic cluster XY model in a transverse magnetic field, where long-range interactions decay algebraically with distance. This model can be exactly solvable within a free fermion framework. By analyzing the gap, we explicitly derive the critical exponents $ν$ and $z$, finding that the relationship $νz = 1$ still holds. However, the values of $ν$ and $z$ depen… ▽ More We investigate a generalized antiferromagnetic cluster XY model in a transverse magnetic field, where long-range interactions decay algebraically with distance. This model can be exactly solvable within a free fermion framework. By analyzing the gap, we explicitly derive the critical exponents $ν$ and $z$, finding that the relationship $νz = 1$ still holds. However, the values of $ν$ and $z$ depend on the decaying exponent $α$, in contrast to those for the quantum long-range antiferromagnetic Ising chain. To optimize scaling behavior, we verify these critical exponents using correlation functions and fidelity susceptibility, achieving excellent data collapse across various system sizes by adjusting fitting parameters. Finally, we compute the entanglement entropy at the critical point to determine the central charge $c$, and find it also varies with $α$. This study provides insights into the unique effect of long-range cluster interactions on the critical properties of quantum spin systems. △ Less

Submitted 6 February, 2025; originally announced February 2025.

Comments: 8 pages, 7 figures

Journal ref: Phys. Rev. A 111, 023307 (2025)

Open Materials Generation with Stochastic Interpolants

Authors: Philipp Hoellmer, Thomas Egg, Maya M. Martirossyan, Eric Fuemmeler, Zeren Shui, Amit Gupta, Pawan Prakash, Adrian Roitberg, Mingjie Liu, George Karypis, Mark Transtrum, Richard G. Hennig, Ellad B. Tadmor, Stefano Martiniani

Abstract: The discovery of new materials is essential for enabling technological advancements. Computational approaches for predicting novel materials must effectively learn the manifold of stable crystal structures within an infinite design space. We introduce Open Materials Generation (OMatG), a unifying framework for the generative design and discovery of inorganic crystalline materials. OMatG employs st… ▽ More The discovery of new materials is essential for enabling technological advancements. Computational approaches for predicting novel materials must effectively learn the manifold of stable crystal structures within an infinite design space. We introduce Open Materials Generation (OMatG), a unifying framework for the generative design and discovery of inorganic crystalline materials. OMatG employs stochastic interpolants (SI) to bridge an arbitrary base distribution to the target distribution of inorganic crystals via a broad class of tunable stochastic processes, encompassing both diffusion models and flow matching as special cases. In this work, we adapt the SI framework by integrating an equivariant graph representation of crystal structures and extending it to account for periodic boundary conditions in unit cell representations. Additionally, we couple the SI flow over spatial coordinates and lattice vectors with discrete flow matching for atomic species. We benchmark OMatG's performance on two tasks: Crystal Structure Prediction (CSP) for specified compositions, and 'de novo' generation (DNG) aimed at discovering stable, novel, and unique structures. In our ground-up implementation of OMatG, we refine and extend both CSP and DNG metrics compared to previous works. OMatG establishes a new state of the art in generative modeling for materials discovery, outperforming purely flow-based and diffusion-based implementations. These results underscore the importance of designing flexible deep learning frameworks to accelerate progress in materials science. The OMatG code is available at https://github.com/FERMat-ML/OMatG. △ Less

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

Comments: Accepted at Forty-second International Conference on Machine Learning (ICML): https://openreview.net/forum?id=gHGrzxFujU

Harnessing Discrete Differential Geometry: A Virtual Playground for the Bilayer Soft Robotics

Authors: Jiahao Li, Dezhong Tong, Zhuonan Hao, Yinbo Zhu, Hengan Wu, Mingchao Liu, Weicheng Huang

Abstract: Soft robots have garnered significant attention due to their promising applications across various domains. A hallmark of these systems is their bilayer structure, where strain mismatch caused by differential expansion between layers induces complex deformations. Despite progress in theoretical modeling and numerical simulation, accurately capturing their dynamic behavior, especially during enviro… ▽ More Soft robots have garnered significant attention due to their promising applications across various domains. A hallmark of these systems is their bilayer structure, where strain mismatch caused by differential expansion between layers induces complex deformations. Despite progress in theoretical modeling and numerical simulation, accurately capturing their dynamic behavior, especially during environmental interactions, remains challenging. This study presents a novel simulation environment based on the Discrete Elastic Rod (DER) model to address the challenge. By leveraging discrete differential geometry (DDG), the DER approach offers superior convergence compared to conventional methods like Finite Element Method (FEM), particularly in handling contact interactions -- an essential aspect of soft robot dynamics in real-world scenarios. Our simulation framework incorporates key features of bilayer structures, including stretching, bending, twisting, and inter-layer coupling. This enables the exploration of a wide range of dynamic behaviors for bilayer soft robots, such as gripping, crawling, jumping, and swimming. The insights gained from this work provide a robust foundation for the design and control of advanced bilayer soft robotic systems. △ Less

Submitted 2 February, 2025; originally announced February 2025.

Comments: 15 pages, 9 figures

Band Structure and Pairing Nature of La$_3$Ni$_2$O$_7$ Thin Film at Ambient Pressure

Authors: Zhi-Yan Shao, Yu-Bo Liu, Min Liu, Fan Yang

Abstract: Recently, evidences of superconductivity (SC) with onset $T_c$ above the McMillan limit have been detected in the La$_3$Ni$_2$O$_7$ ultrathin film grown on the LaSrAlO$_4$ substrate at ambient pressure. This progress opens a new era in the field of the nickelate superconductors. Here we perform a density-functional-theory (DFT) based calculation for the band structure of this material. The obtaine… ▽ More Recently, evidences of superconductivity (SC) with onset $T_c$ above the McMillan limit have been detected in the La$_3$Ni$_2$O$_7$ ultrathin film grown on the LaSrAlO$_4$ substrate at ambient pressure. This progress opens a new era in the field of the nickelate superconductors. Here we perform a density-functional-theory (DFT) based calculation for the band structure of this material. The obtained DFT+$U$ band structure has the feature that the bonding $d_{z^2}$ band crosses the Fermi level, forming the hole pocket $γ$, consistent with the angle-resolved photoemission spectrum (ARPES). Taking the low-energy Ni-$(3d_{z^2},3d_{x^2-y^2})$ orbitals placed on the tetragonal lattice structure, we construct a 2D bilayer four-band tight-binding model which well captures the main features of the DFT+$U$ band structure. Then considering the multi-orbital Hubbard interaction, we adopt the random-phase approximation (RPA) approach to investigate the pairing nature. The obtained pairing symmetry is $s^{\pm}$ or $d_{xy}$ for the hole-doping level $δ$ below or above 0.12, induced by the different Fermi surface nesting situations. For the realistic $δ=0.21$ measured by the ARPES, our RPA calculations obtain the next-nearest-neighbor pairing $d_{xy}$-wave SC dominated by the $d_{z^2}$ orbital, consistent with the experimental observation that the $T_c$ enhances with the shrinking of the in-plane lattice constants. This pairing state is induced by the nesting between the different patches within the $γ$ pocket. Our results appeal for experimental verifications. △ Less

Submitted 6 August, 2025; v1 submitted 6 January, 2025; originally announced January 2025.

Comments: 4.5 pages, 5 figures with Appendix

Journal ref: Phys. Rev. B 112, 024506 (2025)

Beyond the band edge: Unveiling high-mobility hot carriers in a two-dimensional conjugated coordination polymer

Authors: Shuai Fu, Xing Huang, Guoquan Gao, Petko St. Petkov, Wenpei Gao, Jianjun Zhang, Lei Gao, Heng Zhang, Min Liu, Mike Hambsch, Wenjie Zhang, Jiaxu Zhang, Keming Li, Ute Kaiser, Stuart S. P. Parkin, Stefan C. B. Mannsfeld, Tong Zhu, Hai I. Wang, Zhiyong Wang, Renhao Dong, Xinliang Feng, Mischa Bonn

Abstract: Hot carriers, inheriting excess kinetic energy from high-energy photons, underpin numerous optoelectronic applications involving non-equilibrium transport processes. Current research on hot carriers has predominantly focused on inorganic materials, with little attention paid to organic-based systems due to their ultrafast energy relaxation and inefficient charge transport. Here, we overturn this p… ▽ More Hot carriers, inheriting excess kinetic energy from high-energy photons, underpin numerous optoelectronic applications involving non-equilibrium transport processes. Current research on hot carriers has predominantly focused on inorganic materials, with little attention paid to organic-based systems due to their ultrafast energy relaxation and inefficient charge transport. Here, we overturn this paradigm by demonstrating highly mobile hot carriers in solution-processable, highly crystalline two-dimensional conjugated coordination polymer (2D c-CP) Cu3BHT (BHT = benzenehexathiol) films. Leveraging a suite of ultrafast spectroscopic and imaging techniques, we unravel the microscopic charge transport landscape in Cu3BHT films following non-equilibrium photoexcitation across temporal, spatial, and frequency domains, revealing two distinct high-mobility transport regimes. In the non-equilibrium transport regime, hot carriers achieve ultrahigh mobility of ~2,000 cm2 V-1 s-1, traversing grain boundaries up to 300 nm within a picosecond. In the quasi-equilibrium transport regime, free carriers exhibit Drude-type band-like transport with a remarkable mobility of ~400 cm2 V-1 s-1 and an intrinsic diffusion length exceeding 1 micrometer. These findings establish 2D c-CPs as versatile platforms for exploring high-mobility non-equilibrium transport, unlocking new opportunities for organic-based hot carrier applications. △ Less

Submitted 15 January, 2025; originally announced January 2025.

Comments: 27 pages, 4 figures

ABACUS: An Electronic Structure Analysis Package for the AI Era

Authors: Weiqing Zhou, Daye Zheng, Qianrui Liu, Denghui Lu, Yu Liu, Peize Lin, Yike Huang, Xingliang Peng, Jie J. Bao, Chun Cai, Zuxin Jin, Jing Wu, Haochong Zhang, Gan Jin, Yuyang Ji, Zhenxiong Shen, Xiaohui Liu, Liang Sun, Yu Cao, Menglin Sun, Jianchuan Liu, Tao Chen, Renxi Liu, Yuanbo Li, Haozhi Han , et al. (33 additional authors not shown)

Abstract: ABACUS (Atomic-orbital Based Ab-initio Computation at USTC) is an open-source software for first-principles electronic structure calculations and molecular dynamics simulations. It mainly features density functional theory (DFT) and molecular dynamics functions and is compatible with both plane-wave basis sets and numerical atomic orbital basis sets. ABACUS serves as a platform that facilitates th… ▽ More ABACUS (Atomic-orbital Based Ab-initio Computation at USTC) is an open-source software for first-principles electronic structure calculations and molecular dynamics simulations. It mainly features density functional theory (DFT) and molecular dynamics functions and is compatible with both plane-wave basis sets and numerical atomic orbital basis sets. ABACUS serves as a platform that facilitates the integration of various electronic structure methods, such as Kohn-Sham DFT, stochastic DFT, orbital-free DFT, and real-time time-dependent DFT, etc. In addition, with the aid of high-performance computing, ABACUS is designed to perform efficiently and provide massive amounts of first-principles data for generating general-purpose machine learning potentials, such as DPA models. Furthermore, ABACUS serves as an electronic structure platform that interfaces with several AI-assisted algorithms and packages, such as DeePKS-kit, DeePMD, DP-GEN, DeepH, DeePTB, HamGNN, etc. △ Less

Submitted 22 October, 2025; v1 submitted 15 January, 2025; originally announced January 2025.

Non-Hermiticity enhanced topological immunity of one-dimensional $p$-wave superconducting chain

Authors: Min Liu, Yue Zhang, Rui Tian, Xiayao He, Tianhao Wu, Maksims Arzamasovs, Shuai Li, Bo Liu

Abstract: Studying the immunity of topological superconductors against non-local disorder is one of the key issues in both fundamental researches and potential applications. Here, we demonstrate that the non-Hermiticity can enhance the robustness of topological edge states against non-local disorder. To illustrate that, we consider a one-dimensional (1D) generalized Kitaev model with the asymmetric hopping… ▽ More Studying the immunity of topological superconductors against non-local disorder is one of the key issues in both fundamental researches and potential applications. Here, we demonstrate that the non-Hermiticity can enhance the robustness of topological edge states against non-local disorder. To illustrate that, we consider a one-dimensional (1D) generalized Kitaev model with the asymmetric hopping in the presence of disorder. It is shown that the region supporting Majorana zero modes (MZMs) against non-local disorder will be enlarged by the non-Hermiticity. Through both the numerical and analytical analyses, we show that non-Hermiticity can stabilize the topological superconducting (SC) phase against higher disorder strength. Our studies would offer new insights into the interplay between non-Hermiticity and topology. △ Less

Submitted 9 January, 2025; originally announced January 2025.

Many-body interferometry of one-dimensional integrable systems

Authors: Maksims Arzamasovs, Min Liu, Yue Zhang, Rui Tian, Zehou Li, Shuai Li, Bo Liu

Abstract: We propose using many-body Ramsey interferometry to measure non-equilibrium correlation functions of one-dimensional (1D) integrable systems. The 1D transverse-field Ising model, which is conjectured to equilibrate into non-thermal Gibbs ensemble (GGE) steady states, is studied. It is shown that retarded Green's functions, as opposed to ordinary spin-spin correlators considered previously, can con… ▽ More We propose using many-body Ramsey interferometry to measure non-equilibrium correlation functions of one-dimensional (1D) integrable systems. The 1D transverse-field Ising model, which is conjectured to equilibrate into non-thermal Gibbs ensemble (GGE) steady states, is studied. It is shown that retarded Green's functions, as opposed to ordinary spin-spin correlators considered previously, can convincingly distinguish between the GGE and thermal post-quench steady states, justifying the assumption of convergence towards the GGE as the system equilibrates. We also propose the experimental protocol for measuring the response functions with Ramsey interferometry, which can be used to distinguish between different post-quench phases of the model. Our proposal can be realized with current ultracold atom techniques, and opens up the possibility to study dynamics in non-thermal ensembles. △ Less

Submitted 20 December, 2024; originally announced December 2024.

Comments: 5 pages (+ Supplemental), 3 figures

Ultrafast demagnetization in ferromagnetic materials: Origins and progress

Authors: Xiaowen Chen, Roman Adam, Daniel E. Bürgler, Fangzhou Wang, Zhenyan Lu, Lining Pan, Sarah Heidtfeld, Christian Greb, Meihong Liu, Qingfang Liu, Jianbo Wang, Claus M. Schneider, Derang Cao

Abstract: Since the discovery of ultrafast demagnetization in Ni thin films in 1996, laser-induced ultrafast spin dynamics have become a prominent research topic in the field of magnetism and spintronics. This development offers new possibilities for the advancement of spintronics and magnetic storage technology. The subject has drawn a substantial number of researchers, leading to a series of research ende… ▽ More Since the discovery of ultrafast demagnetization in Ni thin films in 1996, laser-induced ultrafast spin dynamics have become a prominent research topic in the field of magnetism and spintronics. This development offers new possibilities for the advancement of spintronics and magnetic storage technology. The subject has drawn a substantial number of researchers, leading to a series of research endeavors. Various models have been proposed to elucidate the physical processes underlying laser-induced ultrafast spin dynamics in ferromagnetic materials. However, the potential origins of these processes across different material systems and the true contributions of these different origins remain challenging in the realm of ultrafast spin dynamics. This predicament also hinders the development of spintronic terahertz emitters. In this review, we initially introduce the different experimental methods used in laser-induced ultrafast spin dynamics. We then systematically explore the magnetization precession process and present seven models of ultrafast demagnetization in ferromagnetic materials. Subsequently, we discuss the physical processes and research status of four ultrafast demagnetization origins (including spin-flipping, spin transport, non-thermal electronic distribution, and laser-induced lattice strain). Since attosecond laser technique and antiferromagnetic materials exhibit promising applications in ultrahigh-frequency spintronics, we acknowledge the emerging studies used by attosecond pules and studies on ultrafast spin dynamics in antiferromagnets, noting the significant challenges that need to be addressed in these burgeoning field. △ Less

Submitted 17 December, 2024; originally announced December 2024.