Materials Science
Materials Acceleration Platform for Electrochemistry: a Platform for Autonomous Electrochemistry
Daniel Persaud, Mike Werezak, Mark Xu et al. (+9 more)
Corrosion testing is slow, labor-intensive, and sensitive to operator technique, limiting the generation of large, high-quality
datasets for data-driven materials discovery. The Materials Acceleration Platform for Electrochemistry (MAP-E) is an autonomous, high-throughput system, capable of performing parallel electrochemical experiments. It integrates robotic
liquid handling, sample transfer with a multi-channel potentiostatic control to extract corrosion metrics without human intervention. Validation against an ASTM G61-analog
benchmark demonstrates good reproducibility, with a standard deviation of 75 mV in pitting potential across 32 automated measurements. The platform was then employed to autonomously construct pH-chloride stability diagrams for 304 stainless steel using an uncertainty-driven sampling strategy on a Gaussian process surrogate model. This approach reduces operator involvement and accelerates the exploration of environmental spaces. The MAP-E establishes a framework for autonomous electrochemical experimentation, enabling generation of corrosion
datasets that inform materials discovery,
alloy design, and durability assessment in service environments.
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All authors Daniel Persaud, Mike Werezak, Mark Xu, Melyne Zhou, Frank Benkel, Xin Pang, Vahid Attari, Brian DeCost, Ashley Dale, Nicholas Senior, Gabriel Birsan, Jason Hattrick-Simpers
Statistical Mechanics
Diffusive flux into a stochastically gated tube
Sean D Lawley
Diffusion-influenced reactions in the presence of gates which randomly open and close have been studied for decades in a variety of biophysical and biochemical scenarios. The diffusive flux from a large bulk reservoir to the end of a narrow tube with a stochastically gated entrance has been previously estimated. In this paper, we extend this gated flux estimate to be valid if (i) the tube is not necessarily narrow and/or (ii) the diffusivity differs in the tube versus the bulk. Extension (i) is challenging because it entails a nontrivial three-dimensional geometry. Extension (ii) is challenging because it introduces multiplicative noise. We derive an explicit flux estimate formula and prove that it is exact in certain parameter regimes. We further use
stochastic simulations to show that the estimate remains accurate across a very broad range of parameters. Our results differ from prior work on extensions (i) and (ii).
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Disordered Systems and Neural Networks · Cross-listed from quant-ph
Self-consistent mean-field quantum approximate optimization
Maxime Dupont, Bhuvanesh Sundar and Meenambika Gowrishankar
We introduce a self-consistent mean-field
quantum optimization
algorithm that approximates the ground state of classical Ising
Hamiltonians. The
algorithm decomposes the problem into independent subproblems and treats the interactions between them in a mean-field manner. These interactions are captured by a common environment, constructed self-consistently through a variational
quantum circuit, and which modifies the subproblems to account for mutual influence while maintaining computational independence. Consequently, subproblems can be solved individually, avoiding the computational cost of the full problem. We explore the properties of the generated environment and assess the
algorithm's performance through extensive numerical simulations on Sherrington-Kirkpatrick
spin glasses. Furthermore, we apply it experimentally to a weighted maximum clique problem applied to molecular docking. This framework enables the solution of problems that would otherwise exceed the
qubit and gate counts of current
quantum hardware.
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Strongly Correlated Electrons
Disorder-Assisted Adiabaticity in Correlated Many-Particle Systems
Shang-Jie Liou and Herbert F. Fotso
We investigate how disorder affects adiabaticity in an interacting
quantum system by assessing its effect on the state of the system after an interaction modulation, or interaction “pulse" ,whereby the interaction is changed from zero to a maximum value and then back to zero following a given time profile. We find that, independently of the disorder strength and pulse shapes (rectangular, triangular, and Gaussian), the pulse duration is negatively correlated with the change in total energy in the system. That is, the longer duration reduces the change in total energy for each protocol. Most importantly, across different considered pulse shapes, we find a robust negative correlation between the disorder strength and the change in total energy across the interaction pulse. Namely, increasing the disorder strength systematically suppresses the residual energy added to the system after the interaction pulse, indicating a more adiabatic response. These two effects, disorder-induced and duration-induced adiabaticity, are consistently observed across all three pulse shapes. Among the protocols, the triangular pulse yields the smallest change in total energy in the system over comparable conditions, demonstrating the most adiabatic response. In addition to the energy analysis, we also examine how disorder modifies the effective temperature change across the interaction pulse, to further establish a quantitative relation between disorder and the thermal response. Altogether, our results identify disorder as a key factor in both the energy and the temperature variation over the time-modulation of the interaction.
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Mesoscale and Nanoscale Physics
Magnetic field tuning of modulated magnetic orders in CrOCl at the two-dimensional limit
T. Riccardi, A. Pawbake, S. Badola et al. (+9 more)
Chromium oxychloride is a van der Waals magnet with intrinsic competing exchange interactions, including a strong
antiferromagnetic one, source of a very rich
magnetic phase diagram, with ferrimagnetic,
antiferromagnetic, and canted states, up to high
magnetic fields. We investigate the sequence of these
magnetic phases in thin layers of CrOCl using magneto-Raman scattering spectroscopy. We identify phases whose
magnetic order is commensurate with the atomic
lattice, and find signatures of strong magneto-striction, presumably of exchange origin. The coupling of the
spin and atomic degrees of freedom in the
crystal is observed down to the single-layer limit –
phonon modes significantly soften or stiffen, in a complex way due to the competition of interactions. The existence domains of the different phases change with the number of layers.
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All authors T. Riccardi, A. Pawbake, S. Badola, F. Petot, B. Grémaud, A. Saul, K. Singh, N.R. Nair, R.S. Chemban, Z. Sofer, J. Coraux, C. Faugeras
Materials Science
Introduction to Spectroscopy of Cr4+:YAG Transparent Ceramics
Mykhailo Chaika
This paper focuses on the spectroscopic properties of Cr4+:YAG transparent ceramic. Absorption, excitation, and emission spectra were measured over a temperature range from 5K to 300K. Low-temperature absorption spectra reveal sharp and narrow lines corresponding to partially allowed transitions from the ground state to the
crystal field splitting components of the 4T2 energy level. The shape of the excitation spectra was found to be independent of the monitored emission wavelength, indicating that Cr4+ emission originates from the lowest excited state. Low temperature emission spectra exhibit a sharp and narrow ZPL, accompanied by the vibronic sidebands extending up to ~2000 cm-1. Both absorption and emission spectra of the lowest excited state at low temperature consist of a doublet, with a splitting of 28 cm-1. The temperature dependence of the spectroscopic parameters of this doublet is reported. Based on the obtained results, possible explanations of its origin are proposed.
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Materials Science
Efficient method for calculation of low-temperature phase boundaries
Lucas Svensson, Babak Sadigh, Christine Wu et al. (+1 more)
Understanding phase stability and phase transformations is central to predicting material behavior under varying thermodynamic conditions. One of the earliest and most influential applications of density functional theory in materials science has been the prediction of pressure-induced phase transitions at 0 K. Extending these calculations to finite temperatures, however, requires accounting for thermal,
quantum, and anharmonic contributions to the free energy, often at significant computational cost. In this work, we present a general and efficient framework for calculating low-temperature phase boundaries by combining the Clausius-Clapeyron equation with the quasi-harmonic approximation. This methodology requires a minimal number of calculations, while naturally incorporating internal degrees of freedom as well as
quantum and low-order anharmonic effects. We illustrate the accuracy and efficiency of the approach by constructing the phase diagram of silica in the pressure range from -2 to 12 GPa and temperatures up to 1750 K. To this end, we employ a machine-learned interatomic potential trained on density functional theory reference data, enabling well-converged free energy estimates via efficient thermodynamic sampling and a rigorous comparison between the proposed framework and free energy integration.
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All authors Lucas Svensson, Babak Sadigh, Christine Wu, Paul Erhart
Materials Science
A new approach for measurement of Cr4+ concentration in Cr4+:YAG transparent materials: some conceptual difficulties and possible solutions
M. Chaika, R. Lisiecki, K. Lesniewska-Matys et al. (+1 more)
In the present work we provide an analysis of the accuracy of the calculation of Cr4+ concentration in Cr4+:YAG using absorption spectroscopy. We propose a new approach based on the convenient optical spectroscopy to estimate the Cr4+ concentration in Cr:YAG using survey absorption spectra. The Smakula Dexter formula is usually used for this purpose. However, the uncertainties in the values of oscillator strengths for Cr4+ absorption bands and, moreover, in the deconvolution of Cr4+ absorption spectra make it difficult to calculate the Cr4+ concentrations with high accuracy.
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All authors M. Chaika, R. Lisiecki, K. Lesniewska-Matys, O. Vovk
Soft Condensed Matter · Cross-listed from physics.flu-dyn
Network modelling of yield-stress fluid flow in randomly disordered porous media
Cláudio P. Fonte, Elliott Sutton, Kohei Ohie et al. (+3 more)
Yield-stress fluid flow through porous media is governed by a strong coupling between rheology and pore-scale geometry, leading to nonlinear, non-Darcy transport and pronounced channelisation near yielding. We develop a pore-network model for Herschel-Bulkley flow in two-dimensional disordered porous media, including optional wall slip. The network is closed by a physics-based pressure-flow relation for a converging-diverging throat, so that yielding and post-yield transport emerge directly from the pore-scale fluid mechanics without fitted resistance parameters. Benchmarking against direct numerical simulations shows that the model captures both the bulk pressure drop and the
evolution of the flow
topology from spatially distributed transport to strongly channelised flow. The framework also captures the leading effect of wall slip, which lowers the pressure gradient required for transport and reactivates pathways that remain blocked in the no-slip case. Using the model across different porous geometries, we show that near-yield pressure losses are governed by constriction statistics rather than by an obstacle-scale length. In particular, rescaling with the domain-averaged minimum throat width collapses the plastic-dominated response across porosities, identifying the dissipation-relevant
geometric scale for viscoplastic transport in this regime.
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All authors Cláudio P. Fonte, Elliott Sutton, Kohei Ohie, Eleanor Doman, Yuji Tasaka, Anne Juel
Soft Condensed Matter
Capillary filling of star polymer melts in nanopores
Jianwei Zhang, Jinyu Lei, Pu Feng et al. (+3 more)
Topology of
polymer profoundly influences on its behavior. However, its effect on imbibition dynamics remains poorly understood. In the present work, capillary filling (during imbibition and following full imbibition) of
star polymer melts was investigated by molecular dynamics simulations with a coarse-grained model. The reversal of imbibition dynamics observed for linear-chain systems was also present for
star polymers.
Star polymers with short arms penetrate slower than the prediction of the Lucas-Washburn equation, while systems with long arms penetrate faster. The radius of gyration increases during confined flow, indicating the orientation and disentanglement of arms. In addition, the higher the functionality of the
star polymer, the more
entanglement points are retained. Besides, a stiff region near the core segments of the
stars is observed, which increases in size with functionality. The proportion of different configurations of the arms (e.g. loops, trains, tails) changes dramatically with the arm length and degree of confinement, but is only influenced by the functionality when the arms are short. Following full imbibition, the different decay rates of the self-correlation function of the core-to-end vector illustrate that arms take a longer time to reach the
equilibrium state as the functionality, arm length, and degree of confinement increases, in agreement with recent experimental findings. Furthermore, the
star topology induces a stronger effect of adsorption and friction, which becomes more pronounced with increasing functionality.
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All authors Jianwei Zhang, Jinyu Lei, Pu Feng, George Floudas, Guangzhao Zhang, Jiajia Zhou
Statistical Mechanics · Cross-listed from hep-th
Capacity of Entanglement and Replica Backreaction in RST Gravity
Raúl Arias and Daniel Fondevila
We compute the capacity of
entanglement in two dimensional dilaton
gravity in a setting where Hawking radiation, backreaction, and islands can be treated analytically. Our focus is the eternal black hole of the Russo Susskind Thorlacius model coupled to N conformal matter fields. Unlike previous gravitational computations, which were mostly carried out in JT
gravity, the RST model forces one to deal with a genuinely dynamical conformal factor and with the global constraints of the replica construction. The main technical step is therefore to solve the replica deformation on the orbifold globally at first order near n=1, including the homogeneous sector fixed by single valuedness and by the requirement of a fixed microcanonical state. For a single interval we obtain a time independent generalized capacity, parallel to the generalized
entropy. For two intervals, even in the late time factorization regime, the global solution generates an interaction term between replica fixed points; after Lorentzian continuation this produces a time dependent capacity on the two QES saddle, despite the corresponding
entropy plateau. We discuss the regime of validity of the resulting expressions and explain how the large size of the two QES capacity implies a highly non uniform saddle competition near n=1, providing a concrete mechanism for sharp features of the capacity at the Page transition.
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Materials Science
Resolving Transient Electron-Phonon Coupling with Time-Resolved Spontaneous Raman Spectroscopy
Guy Reuveni, Maya Levy Greenberg, Matan Menahem et al. (+2 more)
Understanding the interaction of charge carriers with
lattice vibrations in the quasi-
equilibrium regime is crucial for
semiconductor functionality. However, the structural signatures of these interactions are often too subtle for conventional ultrafast techniques to detect. We developed a time-resolved spontaneous Raman technique based on time-correlated single-
photon counting to track the spectral response following photoexcitation, providing sub-wavenumber spectral resolution and a few-hundred-picosecond temporal resolution. Unlike traditional pump-probe schemes, our method utilizes a modulated continuous-wave probe to maintain high spectral resolution, enabling detection of low-frequency Raman shifts down to 10 cm$^{-1}$. Applied to lightly boron-doped silicon, we resolve intra-valence band and inter-valence band electronic transitions. A coupled-mode analysis of transient
phonon asymmetry, resulting from interference with the inter-valence band transitions, reveals electron-
phonon coupling parameters that directly relate to carrier recombination. By capturing these subtle dynamical shifts, we demonstrate that this platform offers a powerful probe for investigating electron-
phonon interactions in long-lived excited states.
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All authors Guy Reuveni, Maya Levy Greenberg, Matan Menahem, Olle Hellman, Omer Yaffe
Quantum Gases
Reproducible nucleation and control of stable quantum vortex rings in Bose-Einstein condensates
Giorgia Iori, Klejdja Xhani, Woo Jin Kwon et al. (+2 more)
We propose and numerically validate an experimentally feasible on-demand protocol for the nucleation and manipulation of stable
quantum vortex rings in trapped Bose-Einstein condensates. The method relies on sweeping a
laser-sheet barrier that locally constricts the superflow and triggers
vortex-ring formation. By tuning the barrier height and width, and by scanning the barrier velocity, we identify the onset of periodic generation of
vortex rings above the critical velocity and achieve direct, deterministic control over the ring nucleation position, radius, and hence propagation speed. After its formation, ad-hoc optical potentials are applied to reshape the
vortex ring, creating clean Kelvin-wave excitations. Our results provide a foundation for systematic studies of three-dimensional
vortices in atomic superfluids and open the door to tailored
vortex dynamics and interactions, enabling controlled access to
quantum turbulence.
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All authors Giorgia Iori, Klejdja Xhani, Woo Jin Kwon, Davide Emilio Galli, Luca Galantucci
Materials Science
AI-driven Inverse Design of Complex Oxide Thin Films for Semiconductor Devices
Bonwook Gu, Trinh Ngoc Le, Wonjoong Kim et al. (+2 more)
Bridging generative foundation models with non-
equilibrium thin-film synthesis remains a central challenge, limiting the practical impact of AI-driven materials discovery on
semiconductor dielectrics. Here, we introduce IDEAL (Inverse Design for Experimental Atomic Layers), an inverse-design platform that links generative
diffusion models, machine learning interatomic potentials, and graph neural network property predictors with atomic layer deposition (ALD). We demonstrate IDEAL using the Hf-Zr-O system as a stringent
benchmark for
semiconductor-relevant complex
oxides. The platform statistically enumerates thermodynamically plausible structures and constructs a composition-structure-property map. Crucially, it identifies a narrow composition window where low-energy tetragonal and orthorhombic phases cluster, revealing trade-offs between band gap and dielectric response. Experimental validation using atomic layer modulation (ALM) corroborates these predictions, demonstrating predictive guidance under realistic, non-
equilibrium thin-film growth. By experimentally closing the loop, IDEAL provides a transferable and generalizable route to the precision synthesis of next-generation
semiconductor dielectrics.
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All authors Bonwook Gu, Trinh Ngoc Le, Wonjoong Kim, Zunair Masroor, Han-Bo-Ram Lee
Mesoscale and Nanoscale Physics
Microscopic origin of $p$-wave magnetism
Johannes Mitscherling, Jan Priessnitz, Clara K. Geschner et al. (+1 more)
$P$-, $f$-, or $h$-wave antialtermagnets yield large non-relativistic
spin splitting with out-of-plane
spin polarization in momentum space perpendicular to the coplanar non-collinear local
magnetic moments. We provide a microscopic explanation of this unconventional
spin polarization by linking it to a previously overlooked site-compensated
spin density that orders antiparallel when projected onto opposite momenta. We verify this result both by model derivation of the out-of-plane momentum-space
spin polarization being proportional to the direct-space cross product of the coplanar non-collinear
spin order, as well as by ab initio calculations in the material candidate CeNiAsO. By providing a general classification and analytic expression for the
spin polarization of all spinful two-site tight-binding
Hamiltonians, we reveal the momentum-resolved
spin polarization as a probe of the Bloch-state geometry arising from
spin-site coupling. Furthermore, our approach allows for
geometric distinction between ferro-, alter-, and antialtermagnets. Our results provide a quantitative guidance for quantized out-of-plane momentum-space
spin polarization and large
spin splitting, and construction principles for antialtermagnets.
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All authors Johannes Mitscherling, Jan Priessnitz, Clara K. Geschner, Libor Šmejkal
Strongly Correlated Electrons
Entanglement Measure Response to Modular Flow and Chiral Topological Phases
Yunlong Zang
Recent years have witnessed significant progress in the
entanglement-based characterization of
quantum phases of matter. The primary objects of interest are the reduced density
matrix and its associated
entanglement Hamiltonian. As intrinsic properties of a
quantum state, these quantities theoretically determine all experimentally accessible local observables. In this work, we investigate the response of two
entanglement measures to the real-time dynamics driven by the
entanglement Hamiltonian–a process known as modular flow. We demonstrate that our results can be unified into a single generating function, $\langle\rho_{AB}^\alpha \mathrm{e}^{\lambda {Q}_{AB}}\mathrm{e}^{\mu{Q}_{BC}}\rho_{BC}^\beta\rangle$. This function is of independent interest as it represents a generalization of the recently proposed Rényi modular commutator. In appropriate limits, this function yields the response of Rényi
entropy and its charged version, which we find to be uniquely determined by
chiral topological invariants, specifically the
chiral central charge and the
Hall conductance. Our analytical findings are validated through two independent approaches: (i) free
fermion systems using the real-space Chern number formula, and (ii) an effective field theory treatment that regularizes the
entanglement cut via
chiral conformal field theory. Both methods yield consistent results.
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Statistical Mechanics
Asymmetric simple exclusion process with tree-like network branches
Yuki Ishiguro and Yasunobu Ando
The asymmetric simple exclusion process (ASEP) is a fundamental
stochastic model describing asymmetric many-particle
diffusion with hard-core interactions on a one-dimensional
lattice, and has been widely applied in the study of nonequilibrium transport phenomena. Motivated by the modeling of
proton transport along oxygen networks in
proton-conducting solid
oxides, we extend the ASEP to a model defined on a one-dimensional backbone
lattice with tree-like network branches. We derive the exact stationary distribution of this network ASEP and investigate its transport properties. By considering two representative network geometries for which physical quantities can be expressed in terms of certain hypergeometric series, we elucidate how the network geometry influences transport properties.
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Materials Science · Cross-listed from cs.LG
Physics-informed neural operator for parametric phase-field modelling of interfacial degradation and microstructural evolution
Nanxi Chen, Airong Chen and Rujin Ma
Predicting interfacial degradation and microstructural
evolution through phase-field modelling is computationally intensive, particularly for parametric studies. While neural operators such as the
Fourier neural operator (FNO) offer a promising route to acceleration, the absence of physical constraints compromises their generalisation and long-term stability. Here, we present PF-PINO, a physics-informed neural operator framework that embeds phase-field governing equation residuals directly into the training loss, together with gradient normalisation loss balancing and a staggered training scheme for coupled multi-field systems. PF-PINO is validated on four
benchmarks including pencil-electrode corrosion, electro-polishing corrosion, dendritic solidification, and spinodal decomposition, collectively probing parametric generalisation across orders-of-magnitude kinetic regimes, non-periodic boundaries with
stochastic morphologies, coupled multi-field dynamics with out-of-distribution extrapolation, and long-term autoregressive stability under complex pattern formation. Across all
benchmarks, PF-PINO reduces relative $L^2$ errors by up to an order of magnitude over FNO and achieves sub-mesh-size interface accuracy, establishing a data-efficient surrogate for high-throughput parametric phase-field assessment in computational materials science and engineering applications.
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Mesoscale and Nanoscale Physics
Gate-tunable anisotropic Josephson diode effect in topological Dirac semimetal Cd$_3$As$_2$ nanowires
Yan-Liang Hou, An-Qi Wang, Na Li et al. (+4 more)
The intrinsic Josephson diode effect (JDE) has recently attracted considerable
attention due to its sensitivity to broken
symmetries in Josephson junctions, offering a powerful probe for uncovering hidden
symmetry-breaking mechanisms in materials. The presence of higher-harmonic components in the current-phase relation, together with
spin-orbital coupling, makes topological materials ideal platforms to explore this effect. In this work, we present a systematic study of the JDE in type-I topological Dirac semimetal Cd$_3$As$_2$ nanowire-based Josephson junctions. We observe a pronounced gate-tunable and highly anisotropic diode response under different
magnetic-field orientations. By developing a comprehensive phenomenological model, we capture the angular dependence of the diode effect and, through temperature-dependent measurements, disentangle the respective contributions from bulk and topological surface states. Notably, anomalies in the temperature dependence of the diode efficiency reveal the coexistence of multiple transport channels, highlighting the Josephson diode effect as a sensitive probe of hidden topological superconducting states.
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All authors Yan-Liang Hou, An-Qi Wang, Na Li, Chun-Guang Chu, Alexander Brinkman, Zhi-Min Liao, Chuan Li
Materials Science
Application of dual-tree complex wavelet transform for spectra background reduction
Kazimierz Skrobas, Kamila Stefanska-Skrobas, Cyprian Mieszczynski et al. (+1 more)
This paper presents a method for background removal in experimental data processing using the Dual-Tree Complex Wavelet Transform (DTCWT). The technique is based on discrete wavelet theory (DWT) and addresses limitations of commonly used numerical approaches, such as fitting or filtering methods. Compared with
Fourier-transform-based techniques, DTCWT provides improved performance for signal extraction. The proposed method is universal and enables analysis of arbitrary data ranges without restrictions on their position in time. It satisfies key requirements of signal analysis, including signal preservation and reduction of processing bias. An
algorithm for background reduction is implemented to extract and enhance meaningful spectral information. The approach is demonstrated on two different types of spectra: X-ray powder diffraction and photoluminescence measured for the $\beta-Ga_{2}O_{3}$
crystal. Practical aspects of DWT-based processing are also discussed, including the selection of wavelet families and decomposition levels. The method is available as a software package for spectral background reduction.
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All authors Kazimierz Skrobas, Kamila Stefanska-Skrobas, Cyprian Mieszczynski, Renata Ratajczak
Strongly Correlated Electrons
Evidence of universal spectral collapse at a marginal dynamical regime
Udomsilp Pinsook, Pakin Tasee and Jakkapat Seeyangnok
Incoherent electronic states in strongly correlated materials are commonly attributed to disorder or material specific mechanisms. Here we show that incoherent spectra instead arise from self-generated dynamical disorder associated with competing fluctuations. In this regime, electron dynamics coupled to time-dependent scattering naturally produce a spectral function of the form rho (z) = exp(-z^2/4) Dnu (z), where z is a scaled energy and Dnu denotes the
parabolic cylinder function. This form reflects a marginal dynamical regime characterized by non-Markovian temporal correlations. Applying this scaling function to angle resolved photoemission spectroscopy (ARPES) energy distribution curves from the cuprates Nd2-xCexCuO4 and Bi2Sr2CaCu2O8+delta, the Kagome metal CsCr3Sb5, and the double-layer nickelate La3Ni2O7, we find that incoherent spectra are quantitatively described by rho (z), differing only in non-universal amplitude and energy scales. After rescaling, the
datasets collapse onto a single universal curve characterized by a fixed
parabolic-cylinder order nu = -1/2. The observed spectral collapse indicates a fixed-point-like regime in which microscopic details such as
lattice geometry, band structure, and chemical composition become irrelevant at low energies. These results establish a unified and quantitative framework for continuum-dominated ARPES spectra across diverse strongly correlated materials.
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Materials Science
Pressure-Induced Structural and Magnetic Evolution in Layered Antiferromagnet YbMn$_2$Sb$_2$
Mingyu Xu, Matt Boswell, Aya Rutherford et al. (+7 more)
Electronic states under pressure exhibit unconventional
spin and charge dynamics that provide a powerful route to uncover exotic phases in
quantum materials. Here, we present the structural,
magnetic, and electronic
evolution of YbMn$_2$Sb$_2$ under pressure. Single-
crystal X-ray diffraction reveals a pressure-induced structural transition from the space group trigonal $P\bar{3}m1$ to the monoclinic $P2_1$/$m$ phase near 3.5 GPa, which remains stable up to 10 GPa. Magnetization measurements display an anomalously weak net
magnetic moment and the absence of Curie-Weiss behavior up to 400 K, suggesting the formation of short-range Mn moment pairs that cancel macroscopically and subsequently evolve into long-range order upon cooling. Temperature-dependent resistivity shows semiconducting behavior with a transition at ~119 K at ambient pressure, while pressure induces a dramatic suppression of resistance and the emergence of metallic-like temperature dependence, stabilized beyond 5 GPa. This pressure-driven
semiconductor-metal transition is consistent with our density functional theory calculations, confirming the closing of the band gap under compression.
Neutron diffraction under pressure identifies an incommensurate
magnetic structure with antiparallel correlations between paired
spins. Together, these results demonstrate how pressure-driven structural tuning and competing exchange interactions stabilize unconventional
magnetic states in this low-dimensional
magnetic semiconductor.
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All authors Mingyu Xu, Matt Boswell, Aya Rutherford, Cheng Peng, Ying Zhou, Shuyang Wang, Zhaorong Yang, Antonio M. dos Santos, Haidong Zhou, Weiwei Xie
Soft Condensed Matter
Three-stage melting of a macroscopic continuous spacetime crystal
Guoqing Liu, Jimin Bai, Matteo Baggioli et al. (+1 more)
A spacetime
crystal is a phase of matter that spontaneously develops periodic order in both space and time. Spacetime
crystals have been experimentally observed in microscopic
quantum many-body systems and, very recently, in a mesoscopic nematic
liquid crystal. However, the melting process of a spacetime
crystal and its underlying physical mechanisms have not yet been experimentally reported. Here, we present a direct observation of a classical continuous spacetime
crystal melting in a table-top experiment with macroscopic active granular disks in 2+1 spacetime dimensions. The spacetime
crystal is characterized by the spontaneous formation of a coherent, rigid-body rotation of a 2D triangular
lattice that persists for almost a day and remains remarkably robust to noise. By tuning the disk packing fraction, we observe a complex three-stage melting process involving a spatially hexatic phase and multiple coexistence regions. Importantly, we show that spatial and temporal crystalline orders melt separately through distinct mechanisms: spatial order is destroyed by the proliferation of topological defects, while temporal order is lost through the decay of directional persistence caused by the progressive weakening of many-body interactions. Our results demonstrate that the spontaneous breaking of spatial and temporal translational
symmetries can be decoupled, leading to the emergence of exotic out-of-
equilibrium classical phases of matter.
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All authors Guoqing Liu, Jimin Bai, Matteo Baggioli, Jie Zhang
Strongly Correlated Electrons
Pressure-Stabilized MnSb$_2$ with Complex Incommensurate Magnetic Order
Mingyu Xu, Matt Boswell, Qing-Ping Ding et al. (+9 more)
Marcasite-type compounds have been proposed as promising hosts of exotic
magnetic quantum states, yet experimental realizations in stoichiometric, disorder-free systems remain limited. Here, we report the high-pressure stabilization and
magnetic characterization of MnSb$_2$, a marcasite-type compound that is thermodynamically metastable under ambient pressure. Single
crystals were synthesized using a cubic multi-anvil press, and powder and single-
crystal X-ray diffraction confirm the orthorhombic $Pnnm$ structure. These
crystals are stable at ambient pressure for a long time up to between 450-500 K. Heat-capacity measurements reveal phase transitions at approximately 220 K and 118 K.
Neutron diffraction uncovers an unconventional
magnetic ground state below 220 K.
Magnetic powder
neutron diffraction refinements reveal possible multiple
magnetic configurations that provide comparably acceptable fits to the experimental data. While most solutions are consistent with a
spin-density-wave (SDW) description, helical models systematically yield inferior agreement factors. Across a broad range of models, the Mn ordered moment reaches a maximum value of approximately 2 $\mu_B$ and remains predominantly collinear, with minimal canting along the $c$-axis. At 200 K, the
magnetic propagation vector is $q$ = (0, 0.3975, 0.3783); upon cooling, the $b$ component increases toward 0.5, reflecting a temperature-dependent
evolution of the modulation. The need for modification of the
magnetic model between high and low temperatures further highlights the complex and strongly temperature-dependent nature of the
magnetic order in this system. These results establish MnSb$_2$ as a pressure-stabilized marcasite magnet with a highly tunable, complex
magnetic ground state and a compelling stoichiometric platform for exploring unconventional
magnetic behavior, including potential altermagnetism.
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All authors Mingyu Xu, Matt Boswell, Qing-Ping Ding, Cheng Peng, Aashish Sapkota, Qiang Zhang, Danielle Yahne, Sergey. L. Bud'ko, Yuji Furukawa, Paul. C. Canfield, Raquel A. Ribeiro, Weiwei Xie
Mesoscale and Nanoscale Physics · Cross-listed from quant-ph
System-bath model for quantum chemistry
Dmitry S. Golubev, Reza G. Shirazi, Vladimir V. Rybkin et al. (+3 more)
We propose an approximate mapping of a molecular
Hamiltonian to a
Hamiltonian of
qubits, which allows for high accuracy
quantum chemistry calculations of vertical excitation energies of some molecules. The mapping is based on separating of a very small active space of only two orbitals and on modeling the electronic excitations in the remaining orbitals by a set of
qubits or, equivalently, by a set of oscillators. This approach is inspired by the Random Phase Approximation (RPA), in which the excitations of electron gas are described by bosonic degrees of freedom. As a result, the
Hamiltonian of the molecule is reduced to that of a system-bath model. The "system" part of the
Hamiltonian describes the two molecular orbitals – the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) – which are populated by two electrons. Two
qubits are sufficient to encode the
Hamiltonian of such a system. The "bath" consists of oscillators or, equivalently, of two level systems with each of them corresponding to an electron excitation from a doubly occupied orbital below the
Fermi level to an empty orbital above the
Fermi level. We hope that this mapping can inspire new approaches and
algorithms aimed at calculating excitation energies of molecules on near term
quantum computers.
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All authors Dmitry S. Golubev, Reza G. Shirazi, Vladimir V. Rybkin, Benedikt M. Schoenauer, Peter Schmitteckert, Michael Marthaler
Soft Condensed Matter
Tunable shear thickening in active frictional non-Brownian suspensions
Bhanu Prasad Bhowmik and Christopher Ness
We study tunable shear thickening in active suspensions of non-Brownian, repulsive, frictional grains using particle-based simulation, finding that activity augments the rheology beyond the friction- mediated shear thickening paradigm. Specifically, up to a crossover activity strength, increasing particle self-propulsion drives a viscosity-reducing `dethickening' of the system at large stresses, where the material would otherwise be in a thickened, highly viscous state. Above this crossover activity strength, the system enters a thickening regime. Self-propulsion introduces additional isotropic dynamics to the particles, which compete with the flow-driven formation of frictional contacts. The degree of dethickening can thus be tuned by varying a suitably-defined dimensionless active stress that quantifies this competition. Recognising the parallels between self-propulsion and other contemporary routes to dethickening, we demonstrate that our data, within the dethickening regime, are consistent with a recently proposed universal scaling framework, offering a route to tuning the rheology of dense suspensions. Moreover, using the obtained scaling relation, we infer how the shear-jamming and shear-thickening regimes can be tuned by choosing an appropriate self-propulsion strength, and partially validate these inferences with targeted simulations.
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Materials Science
Nonlinear Hall Effect in Metal-Organic Frameworks
Sarbajit Mazumdar, Jagadish N S, Awadhesh Narayan et al. (+3 more)
We propose metal-organic frameworks (MOFs) as tunable platforms for nonlinear
Hall responses. A universal analytical downfolding scheme maps $C_3$-symmetric frameworks onto
star- and honeycomb-
lattice models, reproducing first-principles Dirac features.
Spin-orbit coupling and broken inversion
symmetry gap the Dirac cones, generating Berry-
curvature hot spots.
Symmetry analysis identifies tailored synthetic pathways, including linker design, as intrinsic routes to engineer nonlinear
Hall transport beyond strain and substrate control.
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All authors Sarbajit Mazumdar, Jagadish N S, Awadhesh Narayan, Giorgio Sangiovanni, Ronny Thomale, Arka Bandyopadhyay
Strongly Correlated Electrons
Extending the Feynman variational principle and analytical methods to lattice polarons
S. N. Klimin, J. Tempere, M. Houtput et al. (+6 more)
We develop and compare several analytical approximations for the ground state and zero-temperature polaron dispersion in finite-width, nonparabolic conduction bands. The main focus of the work is an extension of the Feynman variational method to a tight-binding
lattice, where the effective-mass approximation is no longer applicable. The resulting variational formulation is not restricted to a specific
phonon dispersion or electron-
phonon interaction and provides a uniform description across weak-, intermediate-, and strong-coupling regimes. In addition, we revisit and generalize other analytical approaches traditionally formulated for continuum polarons, including canonical transformations and self-consistent Wigner-Brillouin-type approximations. For
lattice polarons, these methods exhibit qualitative features absent in the continuum case, such as a nontrivial connection between weak- and strong-coupling limits. We show that an improved Wigner-Brillouin scheme yields a momentum-dependent polaron self-energy free of resonances and in good agreement with numerically exact results. All methods are applied to the Holstein model on a tight-binding
lattice and are benchmarked against numerically exact calculations, including diagrammatic Monte Carlo (both our calculations and preceding works) and exact diagonalization results. Furthermore, the analytical approaches are extended to polarons with Rashba-type
spin-orbit coupling, providing a stringent test of their applicability in systems with nontrivial band structure. Our results demonstrate that the modified Feynman variational method yields ground-state energies and dispersions with accuracy comparable to, and in many cases exceeding, that of other established analytical approaches. The developed framework offers a versatile and reliable analytical description of
lattice polarons beyond the continuum approximation.
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All authors S. N. Klimin, J. Tempere, M. Houtput, I. Zappacosta, S. Ragni, T. Hahn, L. Celiberti, C. Franchini, A. S. Mishchenko
Materials Science
On the origin of diverse interlayer charge redistribution in transition-metal dichalcogenides
Yu-Meng Gao, Nie-Wei Wang, Shi-Xuan Yuan et al. (+3 more)
The interlayer quasi-chemical-bonding (QCB) interactions of two-dimensional (2D) layered materials promote the research field of interlayer-engineering and cause interlayer charge density redistributions (ICDRs). The ICDRs have been reported experimentally and theoretically, which show different redistributions, e.g., accumulation, depletion, or a more complicated behavior. The underlying mechanism for the different ICDRs remain to be elucidated. In the current work, via a systematic theoretical study of the ICDRs of transition metal dichalcogenides with different number of d-electrons filling (d^0 TiS2, d^1 NbS2, and d^2 MoS2) in T and H phases, we reveal three mechanisms based on the coexistence of different types of interlayer QCB interactions. Mechanism (1) is from a competition between two types of interlayer interactions: namely, the interlayer interaction between fully occupied energy levels (in short: o-o interaction) depletes electrons in the overlap region while that between occupied and empty levels (o-e interaction) promotes electron accumulation; and the competition between them leads to that the d^0 TiS2 tends to electron accumulation in T phase than in H phase. Mechanism (2), the interlayer interaction between half-filled levels (h-h interaction) promotes the electron accumulation of d^1 NbS2. Mechanism (3), the interlayer interaction of multiple filled-levels of d^2 MoS2 (namely, the multi-level o-o interaction) leads to a more complicated ICDR. The current study provides a unified understanding to the different ICDRs of van der Waals materials and paves the way for further exploration of their electronic properties and applications.
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All authors Yu-Meng Gao, Nie-Wei Wang, Shi-Xuan Yuan, Wen-Xin Xia, Jiang-Long Wang, Xing-Qiang Shi
Materials Science
Comprehensive structural and optical analysis of differently oriented Yb-implanted $\beta$-Ga$_2$O$_3$
Joanna Matulewicz, Renata Ratajczak, Mahwish Sarwar et al. (+9 more)
This study presents investigations of Yb-doped $\beta$-Ga$_2$O$_3$, an ultrawide bandgap
semiconductor with potential use in future power and optoelectronic devices operating in high-radiation environments. The research has focused on the problem of structural damage caused by the implantation of Yb-ions into three differently oriented
crystals and the optical response of created systems. The (001), (010), and (-201)-oriented $\beta$-Ga$_2$O$_3$
crystals were implanted with three different fluences of 150 keV Yb ions and examined using a variety of experimental techniques: high-resolution X-ray diffraction (HRXRD), Rutherford backscattering spectrometry in channeling mode (RBS/c), Raman and photoluminescence (PL) spectroscopies, to provide comprehensive information about studied systems. Furthermore, the RBS/c studies were supported by Monte Carlo simulations. The results show distinctions between differently oriented
crystals. In particular, (010)-oriented
crystals are characterized by the lowest concentration of extended defects and the presence of compressive stress. In contrast, samples with the other two orientations exhibit tensile stress and significantly higher levels of extended defects. Interestingly, the PL spectra of (010)-oriented $\beta$-Ga$_2$O$_3$ show the lowest emission from Yb$^{3+}$ ions, suggesting that specific types of extended defects, whose formation is more favorable in the other two orientations than in (010), enhance Yb$^{3+}$ luminescence instead of suppressing it.
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All authors Joanna Matulewicz, Renata Ratajczak, Mahwish Sarwar, Ewa Grzanka, Vitalii Ivanov, Damian Kalita, Cyprian Mieszczynski, Przemyslaw Jozwik, Slawomir Prucnal, Ulrich Kentsch, Rene Heller, Elzbieta Guziewicz