Mesoscale and Nanoscale Physics
Tracking thermal transport in colloidal quantum dot films using in-situ time-resolved X-ray diffraction
Eliza Wieman, Nejc Nagelj, Ethan Curling et al. (+9 more)
Colloidal
quantum dots (QDs) and their thin-films are increasingly used in electronic and photonic devices replacing traditional bulk
semiconductors. However, thermal properties of the QDs are comparatively underexplored relative to device development efforts. This study shows the use of time-resolved X-ray diffraction as a contact-free method to probe the thermal response of QDs in device-like environments, providing in-situ insights for future thermal management strategies. Through the extraction of Debye-Waller Factors on a sub-nanosecond timescale, we use time-resolved X-ray diffraction to directly capture the heating and cooling of core/shell CdSe/CdS QDs following pulsed optical excitation. In a QD thin-film that actively provides optical gain, the thermal conductivity is found to be as low as 0.55 $\mathrm{W\,m^{-1}\,K^{-1}}$, because of the poor heat flow within close-packed QD solids. For QDs dispersed in
liquids, interfacial thermal conductance is found to dominate the thermal relaxation with a conductance on the order of 15 $\mathrm{MW\,m^{-2}\,K^{-1}}$.
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All authors Eliza Wieman, Nejc Nagelj, Ethan Curling, Larry Chen, Jin Yu, A. Paul Alivisatos, Aaron Lindenberg, Benjamin T. Diroll, Jacob H. Olshansky, Jihong Ma, Burak Guzelturk, Benjamin L. Cotts
Mesoscale and Nanoscale Physics
Berry-phase effect in single molecule magnets: analytical and numerical results
Fco. Javier Anaya Garcia, Daniel Salgado-Blanco and Gabriel Gonzalez
In this paper we theoretically and numerically investigate transport signatures of
quantum interference on the current through a single molecule magnet transistor tunnel coupled to oppositely polarized leads in the presence of a local transverse and longitudinal
magnetic field. Our calculations are based in a density
matrix approach where we treat the ground state energy splitting induced by tunneling of the
spin between different paths with the aid of perturbation theory. Using this approach we show that it is possible to use an effective
Hamiltonian which describes the Berry phase interference as a function of the transverse
magnetic field which completely blocks the current flow when we place the single molecule magnet between oppositely polarized leads. Finally, we use this effective
Hamiltonian in an open source Python software (QmeQ) that allows us to calculate the current through the single molecule magnet with oppositely polarized leads tunnel coupled to the single molecule magnet. The analytical results are well reproduced by our numerical simulations.
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Mesoscale and Nanoscale Physics
Topological flat bands emerging at the inversion of stacking order in rhombohedral graphite
R. Weht, A. A. Aligia and M. Nunez-Regueiro
Motivated by the indications of high-Tc superconductivity in natural graphite enriched in the rhombohedral phase, we study the band structure of several stacking configurations that combine two of the three graphite structures as well as modifications of the rhombohedral sequence (from ABCABC... to CBACBA...), using first-principles calculations. We focus in particular on the possible emergence of flat bands near the
Fermi level. When the two different rhombohedral orderings are combined, flat bands of topological origin emerge at the interface between the two domains, near the K and K' points of the Brillouin zone. Mapping a simple tight-binding model of a rhombohedral slab along the direction perpendicular to the
graphene layers onto a Su-Schrieffer-Heeger chain provides a transparent understanding of the underlying physics.
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Disordered Systems and Neural Networks · Cross-listed from cs.LG
Diffusion Operator Geometry of Feedforward Representations
Kanishka Reddy
Feedforward neural networks transform data through learned representations whose geometry shapes how classes separate and relate across successive layers. We study that geometry through
diffusion operators. Each feature-cloud snapshot is assigned a Gaussian-kernel Markov operator, giving a smooth description of one-step transport between classes from which spectral, boundary, and local
geometric information can be read. We define the empirical class chain, state the condition under which it is an exact Markov quotient, and derive both the corresponding population transition and a simpler overlap chain based on expected class affinities. For balanced shared-covariance Gaussian class-conditional snapshots these affinities have closed forms controlled by a regularized Mahalanobis separation, which yields explicit expressions for leakage and coarse spectral behaviour. We further show that operator observables vary smoothly under feature perturbations, whereas hard neighborhood graphs are controlled by neighbor-order margins. Experiments on CIFAR-10 and CIFAR-100 ResNet-18 representations find that class transport becomes increasingly persistent with depth while retaining structured relations between classes, and that the
diffusion class chain is more stable than its $k$-nearest-neighbor counterpart under matched perturbations.
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Materials Science
Experimental investigation of altermagnetic order in Cr-doped FeSb2
A K M Ashiquzzaman Shawon, Eoghan Downey, Shane Smolenski et al. (+16 more)
Altermagnets are a class of materials with compensated
magnetic moments, in which
spin sublattices are related by specific rotational
symmetries other than inversion or translation. This allows time-reversal
symmetry to be broken without a net magnetization. Cr-doped FeSb2 has been theoretically proposed as a candidate d-wave altermagnetic system, yet its
magnetic ground state has remained unresolved. Here, we synthesize single
crystals of Fe1-xCrxSb2 and investigate their electrical transport and
magnetic properties, with a focus on Fe0.85Cr0.15Sb2. Magnetization measurements suggest
spin-compensated ordering below ~3.5 K, where
magnetic moments align along the crystallographic b-direction. Transport measurements reveal a crossover from large positive to negative magnetoresistance, while an anomalous
Hall response emerges below 5 K, indicating time-reversal
symmetry breaking.
Muon spin relaxation measurements confirm that the
magnetic ordering below 3.5 K is bulk in nature. The absence of coherent oscillations in zero-field {\mu}SR spectra and of
magnetic Bragg intensity in single-
crystal neutron diffraction establishes that the magnetically ordered state is short-range or disordered, rather than collinear altermagnetic order. These results demonstrate that Cr-doping alone breaks time-reversal
symmetry without stabilizing long-range altermagnetic order in FeSb2.
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All authors A K M Ashiquzzaman Shawon, Eoghan Downey, Shane Smolenski, Thomas J. Hicken, Tatenda Kanyowa, Amir Henderson, Si Athena Chen, Mingyu Xu, Trisha Musall, Rafael Lopes Sabainsk, Zachary J. Morgan, Wei Tian, Yuan Zhu, Weiwei Xie, Elena Gati, Lu Li, Zurab Guguchia, Huibo Cao, Na Hyun Jo
Mesoscale and Nanoscale Physics
Non-Equilibrium Thermodynamic Extremal Principles During Filament Formation in ECM Memristors
Justin Brutger and Xiao Shen
Electrochemical metallization (ECM) memristors have potential applications in future neuromorphic computing hardware. The set, reset, and variable-resistance features of these devices originate in the formation and breakup of metal filaments in a solid-state electrolyte. While the performance characteristics of these devices are widely investigated, the driving principles behind the morphology of the filament formation process remain unclear. In this study, we propose an approach motivated by the extremal principles found in non-
equilibrium thermodynamics and observe an
entropy production and energy dissipation rate minimization during the filament-forming process in kinetic Monte Carlo simulations.
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Materials Science · Cross-listed from physics.chem-ph
Stochastic Cluster Expansion for Excited State Energies
Annabelle Canestraight, Russell Miller, Libor Veis et al. (+1 more)
Excited-state electronic structure in strongly correlated systems remains challenging due to the exponential scaling of the many-body
Hilbert space and the difficulty of constructing systematically controlled active spaces. Building on the
stochastic cluster expansion (SCE) framework previously developed for ground-state correlation energies, we extend the formalism to excitation gaps by expressing energy differences directly as a hierarchy of orbital-space cluster contributions. In this formulation, excitation energies are reconstructed from reduced-rank calculations involving a minimal frontier chemical subspace (FCS), treated exactly, together with
stochastic sampling of the remaining orbital environment. This approach eliminates the need for large or chemically preselected active spaces. We demonstrate the method on charge-transfer complexes and polyacenes, where accurate singlet-triplet gaps are obtained that agree with full-system results. The method converges with low-order cluster terms and provides a systematically improvable framework for excited states in correlated systems.
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All authors Annabelle Canestraight, Russell Miller, Libor Veis, Vojtech Vlcek
Mesoscale and Nanoscale Physics · Cross-listed from physics.optics
Two-Photon-Induced Direct 3D Printing of Freeform High-Index Phase-Change Sb2S3 Nanostructures
Abhrodeep Dey, Andrea Dellith, Anne Sauer et al. (+7 more)
Chalcogenides have recently emerged as an important class of phase-change materials (PCMs) for nanophotonics, owing to their very high refractive index (RI) and low optical loss in the visible to near-infrared range. They exhibit an ultralarge RI change (> 0.7) upon phase transition, which can be triggered by multiple stimuli such as electrical bias,
laser illumination or thermal heating. These properties make them highly appealing materials for flat optics and metasurface applications. Current nanophotonic implementations of chalcogenide PCMs mostly rely on two-dimensional (2D) or quasi three-dimensional (3D) thin film patterning based on the coating of chalcogenide materials from a solid-state target. This limits fast prototyping of 3D freeform micro- and nanostructures, thus restricting
geometric design freedom and device functionality. Here, we demonstrate a solution-phase direct printing of chalcogenide PCMs into functional structures. The method is based on dip in two
photon-induced solidification (DITPS) of a specially synthesized antimony trisulfide (Sb2S3) precursor solution. Direct printing with DITPS is simple, maskless, fast and cost effective, enabling true freeform 3D printing of photonic devices with sub micron resolution. We show direct writing of Sb2S3 helices with different wire cross section profiles on gold and ITO substrates, as well as functional planar Fresnel zone plates (FZPs) and computer generated hologram metasurfaces (CGHMs) in a single printing step. This freeform DITPS approach thus enables rapid 3D prototyping of high index metasurfaces and opens a route to integrating high-index PCMs into existing photonic architectures and device platforms.
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All authors Abhrodeep Dey, Andrea Dellith, Anne Sauer, Uwe Hübner, Henrik Schneidewind, Markus A Schmidt, Astrid Bingel, Volker Deckert, Jer-Shing Huang, Wei Wang
Materials Science
A hidden bulk polymorph governs charge transport dimensionality in an organic semiconductor
Caterina Zuffa, Marco Bardini, Fabian Gasser et al. (+11 more)
Organic
semiconductors (OSCs) are widely explored for flexible optoelectronic technologies, with performance governed not only by molecular design, but also by solid-state packing, which can give rise to polymorphism. Dinaphthothienothiophene (DNTT) is a
benchmark OSC that has long been considered monomorphic. Here, we discover, isolate, and resolve the
crystal structure of a previously unrecognised bulk polymorph of DNTT, termed blue DNTT owing to its characteristic blue emission. Coexisting with the well-known (green) DNTT in commercial powders, yet previously overlooked, blue DNTT represents the thermodynamically stable form. By combining X-ray diffraction, Raman, and THz spectroscopy with simulations, we demonstrate that polymorphism in DNTT reshapes the low-frequency
phonon landscape and transfer-integral network, impacting charge transport. While green DNTT exhibits two-dimensional charge transport with holes more mobile than electrons, blue DNTT shows charge transport along all crystallographic directions enabled by a distinct herringbone packing. Electron mobility along the crystallographic a and b-axes in blue DNTT exceeds twice the hole mobility in the green phase. To our knowledge, this is the first reported acene-based
semiconductor exhibiting three-dimensional charge transport. Polymorphism emerges as a key lever to tune charge transport dimensionality and carrier efficiency in organic
semiconductors.
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All authors Caterina Zuffa, Marco Bardini, Fabian Gasser, Mauricio Sevilla, Robinson Cortes-Huerto, Alessandro Greco, Lorenzo Soprani, Guanzhao Wen, Jaco J. Geuchies, Mischa Bonn, Gabriele D'Avino, Lucia Maini, Hai I. Wang, Lucia Di Virgilio
Materials Science
Understanding the lifetime of water with dynamic network analysis: the case of CsOH.H2O
Graeme J. Ackland, Ciprian G. Pruteanu, John S. Loveday et al. (+1 more)
We describe the atomic-level motions in caesium hydroxide monohydrate (CsOH$\cdot$H$_2$O), which is a chemical compound containing layers of water and hydroxide ions. At this composition, each oxygen is involved in three hydrogen bonds which, in the hexagonal structure, form a quasi-2D honeycomb
lattice. While oxygen and caesium atoms form a typical
crystal lattice, the dynamics of the hydrogen atoms are more complex. Here we show that the covalent and hydrogen bonds are continually interconverting, meaning that the water and hydroxyl are interconverting by
proton exchange. The order-disorder transition of the water and hydroxyl proceeds by chemical reaction rather than rotation or
diffusion of the molecules. A hydrogen can rotate out of the layer, leaving a vacant site in the 2D layer. Such a hydrogen vacancy can diffuse rapidly by single molecule rotation, leading to fast-ionic conduction. The
proton exchange leads to a novel type of Raman activity combining stretch and exchange processes, for which we develop a theoretical model. This would manifest in a broad single peak associated with both H$_2$O and OH stretches and a low frequency peak appearing at elevated temperature.
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All authors Graeme J. Ackland, Ciprian G. Pruteanu, John S. Loveday, Keishiro Yamashita
Strongly Correlated Electrons
Manipulation of electromagnetic wave propagation in quantum-spin-chain medium
Taras Krokhmalskii, Taras Verkholyak, Ostap Baran et al. (+3 more)
We consider a simple model of one-dimensional
magnetic crystal and examine the propagation of an electromagnetic wave through such a medium. Calculating the dispersion relation ${\bf k}(\omega)$ allows us to illustrate how the spread of the electromagnetic wave can be controlled by an external
magnetic field. Our rigorous calculations should be useful for more realistic (and less tractable mathematically) models of
magnetic media.
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All authors Taras Krokhmalskii, Taras Verkholyak, Ostap Baran, Dmytro Yaremchuk, Taras Hutak, Oleg Derzhko
Materials Science
Influence of Coherent Elastic Strain on Phase Separation in BCC Nb-V Alloys
Siya Zhu and Raymundo Arróyave
Coherent elastic strain is an important but often neglected contribution to phase-separation thermodynamics in
alloy systems where decomposed phases have appreciable
lattice mismatch. We develop a thermodynamic framework that incorporates coherent elastic compatibility directly into phase-diagram calculations alongside conventional CALPHAD chemical free energies. Applied to the BCC Nb-V system, the framework shows that coherent elasticity substantially suppresses phase separation, narrows the miscibility gap, and lowers the critical temperature toward experimentally observed values. Beyond these quantitative effects, the coherent constraint qualitatively alters the interpretation of phase
equilibria: the
equilibrium decomposition compositions become functions of both temperature and overall
alloy composition, so the two-phase boundary no longer represents unique coexistence compositions. These results establish coherent elasticity as a key thermodynamic factor in
lattice-mismatched systems and provide a general framework for coherent phase-diagram modeling.
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Strongly Correlated Electrons
Model-agnostic cooling algorithms for strongly interacting fermions
Henning Schlömer, Liyuan Chen, Susanne F. Yelin et al. (+1 more)
Strongly interacting
fermions underpin some of the most challenging problems in condensed matter physics, such as high-temperature superconductivity. The low-energy states of these systems encode their essential microscopic properties, yet remain largely inaccessible to classical methods.
Quantum simulation offers a promising path forward, and among state-preparation strategies, engineered dissipation has emerged as a particularly compelling approach. Existing cooling protocols, however, typically rely on knowledge of the quasiparticle spectrum or mappings to free-
fermion limits. In this letter, we introduce a randomized,
symmetry-preserving cooling
algorithm that requires no spectral information, using only local coupling operators to ancilla degrees of freedom with randomly sampled energy splittings to drive generic fermionic systems toward their low-energy
manifold. We
benchmark the protocol on canonical correlated fermionic models relevant to high-temperature
superconductors, spanning metallic, density-wave, paired, superconducting, and phase-separated phases. Across all models, we observe universal cooling behavior: monotonic energy relaxation, concentration of spectral weight at low energies, and stabilization of correlated ground-state order. Our results establish randomized dissipative cooling as a general strategy for preparing strongly correlated fermionic states on programmable
quantum devices.
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All authors Henning Schlömer, Liyuan Chen, Susanne F. Yelin, Hong-Ye Hu
Strongly Correlated Electrons · Cross-listed from quant-ph
Universality of Quantum Gates in Particle and Symmetry Constrained Subspaces
Andreas Stergiou and Nicolas PD Sawaya
Simulating physical systems on near-term
quantum computers often requires preparing states within constrained subspaces, like those with fixed particle number or
spin. We use Lie algebraic techniques to prove that hardware-efficient gates are universal for state preparation in these subspaces. The key mechanism is Pauli $Z$ dressing: commutators of overlapping gates produce Pauli $Z$ operators on shared
qubits, acting as spectator projectors that decompose multi-plane rotations into single-plane generators spanning the full $\mathfrak{so}(w)$
algebra, where $w$ is the dimension of the constrained subspace, thereby guaranteeing universality for real state preparation. Adding independent complex phases extends this to $\mathfrak{su}(w)$, enabling arbitrary complex state preparation. We provide a computationally efficient Jacobian criterion for verifying that a
circuit can explore any direction on the target
manifold from almost any parameter configuration. Our findings are applicable to many problem areas, including
Fermi-Hubbard models, Bose-Hubbard models, and molecular electronic structure. We apply our framework to two physical settings: we prove the completeness of the binary encoded multi-level particles ansatz on the conserved-particle-number subspace, and we construct
symmetry-preserving
circuits for the fuzzy sphere regularisation of the 3D Ising conformal field theory (CFT). For the latter, we variationally prepare the ground and excited states and extract some CFT data.
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Statistical Mechanics
The Mesoscopic Partition Function:A Combined Spatial and Phase-Space Cell Structure
Bob Osano
We develop a mesoscopic formulation of
equilibrium statistical mechanics based on coarse-grained occupation-number sectors of one-particle phase space. A mesoscopic partition function is constructed by averaging the microscopic
Hamiltonian over configurations compatible with a given occupation profile. The construction converges to the canonical Gibbs partition function in the fine-graining limit and remains compatible with interacting many-body systems. Within this framework, thermodynamic extensivity is shown to be equivalent to asymptotic factorisation of the mesoscopic partition function, while residual inter-
cell correlations generate subextensive corrections. The resulting formalism provides a mathematically consistent bridge between microscopic Gibbs theory and mesoscopic thermodynamics.
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Materials Science
Revealing the origin of XMCD in an altermagnet via three-dimensional control of spins
Daire Mallon, Zixuan Wu, Jheng-Cyuan Lin et al. (+15 more)
Altermagnets are an emerging class of collinear antiferromagnets that exhibit unconventional
spin-polarised electronic bands, potentially unlocking new functionalities that do not rely on
spin-orbit coupling (SOC). Experimental signatures traditionally associated with
spin polarisation, like X-ray
magnetic circular dichroism (XMCD), are thus being used as a validation of altermagnetism. However, unlike altermagnetic
spin-splitting, these responses require SOC and are not invariant under
spin-space rotations. This brings into question the extent to which they can be considered direct signatures of altermagnetism. Here, we exploit the g-wave altermagnet $\alpha$-Fe$_{2}$O$_{3}$ to demonstrate that XMCD is governed precisely by the
spin-direction-induced
symmetry breaking that altermagnetic
spin groups are designed to ignore. Strikingly, the XMCD is highly anisotropic and is decoupled from the weak
magnetic canting. We show that this anomalous XMCD can be described by on-site Faraday tensors capturing the locally uncompensated
spin-orbital anisotropies - a scenario that can be applied to other altermagnets. Leveraging this, we reconstruct complete vectorial maps of nanoscale textures in $\alpha$-Fe$_{2}$O$_{3}$ thin films, including domain walls and topological
solitons, which are promising for building future spintronics and magnonics devices.
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All authors Daire Mallon, Zixuan Wu, Jheng-Cyuan Lin, Ruiwen Xie, Bo Zhao, Charles Godfrey, Qing He, Lucia Iglesias, Pierluigi Gargiani, Manuel Valvidares, Peter Bencok, Francesco Maccherozzi, Larissa S. I. Veiga, Paul Steadman, Manuel Bibes, Hongbin Zhang, Paolo G. Radaelli, Hariom Jani
Statistical Mechanics · Cross-listed from physics.bio-ph
Statistical mechanics for Scrabble predicts strategy, entropy and language
Olivier Witteveen and Marianne Bauer
The crossword-like patterns of tiles in Scrabble form connected graphs of occupied sites on a square
lattice. We find the most structureless description that reproduces means and covariances observed in real Scrabble games by adapting a maximum
entropy approach to connected graphs. This pairwise model captures the data well, and predicts word-length statistics and
geometric features of the Scrabble graphs correctly; in addition, the parameters of this model are interpretable and allow us to understand Scrabble playing strategies. Using this pairwise model, we calculate
entropy differences and distinguishability of Scrabble graphs across
languages, without having access to the letters on the tiles. Notably, we find that the
entropy is predicted better by strategic gameplay – such as word length on the board – than lexicon size. Finally, we find that we can use the pairwise model to correctly assign Scrabble graphs to
languages, avoiding explicit feature selection and at relatively low computational cost.
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Materials Science · Cross-listed from cs.CL
Can Coding Agents Reproduce Findings in Computational Materials Science?
Ziyang Huang, Yi Cao, Ali K. Shargh et al. (+15 more)
Large
language models are increasingly deployed as autonomous coding
agents and have achieved remarkably strong performance on software engineering
benchmarks. However, it is unclear whether such success transfers to computational scientific workflows, where tasks require not only strong coding ability, but also the ability to navigate complex, domain-specific procedures and to interpret results in the context of scientific claims. To address this question, we present AutoMat, a
benchmark for evaluating LLM-based
agents' ability to reproduce claims from computational materials science. AutoMat poses three interrelated challenges: recovering underspecified computational procedures, navigating specialized toolchains, and determining whether the resulting evidence supports a claim. By working closely with subject matter experts, we curate a set of claims from real materials science papers to test whether coding
agents can recover and execute the end-to-end workflow needed to support (or undermine) such claims. We then evaluate multiple representative coding
agent settings across several foundation models. Our results show that current LLM-based
agents obtain low overall success rates on AutoMat, with the best-performing setting achieving a success rate of only 53%. Error analysis further reveals that
agents perform worst when workflows must be reconstructed from paper text alone and that they fail primarily due to incomplete procedures, methodological deviations, and execution fragility. Taken together, these findings position AutoMat as both a
benchmark for computational scientific reproducibility and a tool for diagnosing the current limitations of agentic systems in AI-for-science settings.
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All authors Ziyang Huang, Yi Cao, Ali K. Shargh, Jing Luo, Ruidong Mei, Mohd Zaki, Zhan Liu, Wyatt Bunstine, William Jurayj, Somdatta Goswami, Tyrel McQueen, Michael Shields, Jaafar El-Awady, Paulette Clancy, Benjamin Van Durme, Nicholas Andrews, William Walden, Daniel Khashabi
Materials Science
Determination of Density Functional Tight Binding Models for Cerium-containing Materials
Nir Goldman, Artem Samtsevych and Chiara Panosetti
We have developed Density Functional Tight Binding models for cerium and cerium
oxide with generalized gradient approximation and hybrid functionals that accurately predict the electronic band structure of different cerium polymorphs as well as the insulating
oxide. We show that determination of a many-body repulsion energy with the Chebyshev Interaction Model for Simulation correctly predicts cerium allotropic energetic ordering with a minimal training created from small-scale molecular dynamics calculations of a single phase, only. Our approach determines DFTB models for both electronic and material property predictions that retain a high degree of transferability.
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Materials Science
Oxygen Vacancies at Dislocation Core Modulate Plasticity in Strontium Titanate
Min-Chul Kang, Chunxu Yan, Alexander Frisch et al. (+3 more)
Dislocation core chemistry in
oxides critically influences mechanical behavior and functionality; yet the
evolution of core chemistry during the dislocation motion in them has not been directly observed. Here, using SrTiO3 as a model material, we combine aberration-corrected scanning transmission electron microscopy and electron energy-loss spectroscopy with atomic-level molecular dynamics (MD) simulations to correlate the <110>{1-10} dislocation core structure, oxygen vacancy density, charge state, and mobility with each other. We find that the mechanically induced dislocation loops exhibit dissociated cores, whose oxygen vacancy density depends on the gliding distance: short loops are Ti-reduced and oxygen-deficient at the edge dislocation core, whereas longer loops remain close to stoichiometry in both the edge and screw components. MD simulations reveal that kink-assisted edge dislocation glide in SrTiO3 leaves oxygen-deficient trails behind, modulating the oxygen content inside the edge core. These results demonstrate that oxygen-vacancy
evolution at the dislocation core intrinsically couples with plasticity in ionic
crystals, suggesting a mechanism for oxygen vacancy-dependent dislocation mobility in plastically deformed
oxides.
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All authors Min-Chul Kang, Chunxu Yan, Alexander Frisch, Xufei Fang, Liming Xiong, Lin Zhou
Statistical Mechanics · Cross-listed from quant-ph
Entanglement capacity of complex networks from quantum walks
Pravy Prerana and Sascha Wald
Discrete-time
quantum walks provide a natural framework for
quantum transport on complex networks. On regular structures, coin-walker
entanglement has been widely used to characterize
quantum transport and to support
quantum algorithmic protocols. However, this notion relies on a fixed
Hilbert space factorization separating coin and position and is therefore not directly applicable to more complex, irregular structures. Here we introduce an
entanglement measure for general networks based on a bipartition that assigns each node two roles, acting as both a source and a target. The resulting bipartition defines the source-target
entanglement, a measure for general networks, motivated by coin-walker
entanglement. We show that the connectivity of the network imposes an upper bound on this
entanglement and identify graph matchings as the underlying structure governing
entanglement generation. We further illustrate that in random graphs improving graph connectivity reduces the attainable
entanglement, establishing a structure-dependent constraint on
quantum correlations.
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Quantum Gases · Cross-listed from quant-ph
Topological protection of local quantum Fisher information
Marcin Płodzień and Jan Chwedeńczuk
In many-body
quantum systems,
unitary dynamics generically delocalize locally encoded information, causing single-site metrological sensitivity to vanish. We analytically demonstrate that a topological phase can prevent this dispersal. In the open Kitaev chain, a Majorana zero mode fixes the boundary
quantum Fisher information (QFI) at a nonzero plateau that persists for times exponentially long in system size. We derive exact analytical expressions for the local QFI and identify the mechanism as the spatial separation of the two Majorana quadratures to opposite ends of the chain. This separation produces a boundary encoding-axis asymmetry that distinguishes topological boundary
memory from a generic localized subgap signal. We show numerically that the asymmetry is robust to moderate quenched on-site disorder, while the boundary plateau remains visible under parity-preserving interactions in finite-size real-time simulations. The protocol requires only product-state initialization,
Hamiltonian evolution, and single-site readout.
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Statistical Mechanics
Reconstruction of spin structures from topological charge distributions via generative neural network systems
Kyra H. M. Klos, Jan Disselhoff, Michael Wand et al. (+2 more)
Localized topological defects inherently possess a multiscale character. While their microstructure configuration depends on the specific physical system, their topological features and mutual interactions can be described on the macroscale in terms of a particle representation. However, determining the physical properties associated with a given defect pattern often requires knowledge of the underlying microscopic structure. In this work, we extend a Wasserstein generative
adversarial neural network by incorporating physical constraints and
Fourier-space information to generate microscopic
spin configurations consistent with prescribed macroscopic patterns and thermodynamic parameters. Using the two-dimensional XY model as a test case, where
vortex-antivortex pairs act as long-range interacting defects, we show that the model generates
spin configurations that accurately reproduce magnetization, susceptibility, helicity modulus, and
spin-
spin correlations over a wide range of temperatures below the Kosterlitz-Thouless transition. At the same time, deviations in the specific heat reveal limitations in reproducing higher order energy fluctuations. A complementary analysis based on topological data analysis uncovers subtle differences in global
spin-correlation structures at near critical temperatures that are not apparent from conventional correlation functions alone. These results demonstrate both the promise and current limitations of generative approaches for multiscale studies of defect-dominated
spin systems and at the same time highlight topological methods as valuable tools for characterizing critical behavior.
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All authors Kyra H. M. Klos, Jan Disselhoff, Michael Wand, Karin Everschor-Sitte, Friederike Schmid
Materials Science
TrueEBSD in MTEX: automatic image matching for correlative microscopy applications
Vivian Tong, Stefan Olovsjö, Rachid M'Saoubi et al. (+3 more)
TrueEBSD is an open-source MATLAB program for image
alignment and spatial distortion correction of images and electron backscatter diffraction (EBSD) maps. We have re-implemented TrueEBSD as an add-on to MTEX, an established toolbox for EBSD data analysis. Spatial
alignment enables correlative analysis methods, such as augmenting EBSD orientation maps with data from other imaging modes. The augmented EBSD maps can then be analysed further using MTEX. We demonstrate TrueEBSD on two example case studies: one for measuring Co phase fraction and WC contiguity in a WC-Co composite, and another for determining the relative susceptibility of grain boundaries to void formation in a copper polycrystal. In both examples, the EBSD map was augmented with scanning electron microscopy (SEM) image data. This enabled quantitative crystallographic measurements which would not be possible from analysing the EBSD maps and images separately.
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All authors Vivian Tong, Stefan Olovsjö, Rachid M'Saoubi, Mathias Grabner, Manuel Petersmann, Liam Wright
Quantum Gases
Entropy transport through a superfluid quantum point contact: A Keldysh field-theory approach
Davide Bertolusso, C.J. Bolech and Thierry Giamarchi
We study the matter and
entropy transport between two ultra-cold neutral
Fermi-gas reservoirs linked by a
quantum point contact under a chemical-potential gradient. We describe the two leads with a BCS mean-field model and derive the current-bias characteristics for both particle and
entropy transport. We compute the out of
equilibrium steady-state currents by using the Keldysh formalism. In accordance with previous works in the literature, we confirm the well-known behavior for the particle current and extend the computation to the
entropy current in the BCS regime. The
entropy current shows an oscillatory behavior at low voltage in the ballistic junction limit. We analyze the results for a wide range of values of the junction's transparency. We also compare our findings with experimental results in cold atomic gases in the
unitary regime.
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Mesoscale and Nanoscale Physics
Experimental Evidence of Fractional Entropy in Critical Kondo Systems
C. Piquard, A. Veillon, Y. Sato et al. (+7 more)
Unconventional
quantum states defying the ubiquitous
Fermi-
liquid paradigm can emerge in the presence of strong electronic correlations. Among these, non-Abelian anyons - such as Majorana zero modes and Fibonacci anyons - are of particular interest for topological
quantum computing due to their non-integer
quantum dimensions d>1, which allows for protected non-local encoding and processing of
quantum information. However, despite considerable efforts, the unambiguous characterisation of such anyons via transport measurements has proved challenging. Instead, here we provide experimental evidence for the low-temperature fractional
entropy Delta S associated with a single anyon, which directly implies its non-Abelian character through the relation Delta S = kB ln(d). This thermodynamic signature is measured in metal-
semiconductor quantum circuits engineered to realize
quantum-critical states from frustrated interactions. Using a micrometre-scale metallic island coupled to two or three electronic leads, we tune the system to two-channel and three-channel Kondo critical points. By measuring the island charge and exploiting a thermodynamic Maxwell relation, we estimate the
entropy associated with the anyons that emerge in these critical states. Our observations reveal fractional values, exposing non-Abelian anyons. The corresponding scaling dimensions are consistent with theoretical predictions for a Majorana zero mode Delta S = kB ln(sqrt(2)) and a Fibonacci anyon Delta S = kB ln(1 +sqrt(5))/2 for two and three channels. These findings establish
entropy measurements as a powerful tool for characterizing exotic
quantum states.
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All authors C. Piquard, A. Veillon, Y. Sato, F. Zanichelli, A. Aassime, A. Cavanna, U. Gennser, A. K. Mitchell, A. Anthore, F. Pierre
Soft Condensed Matter
Architecting mechanosensitive nanofluidic transport in graphite nanoslits
Mathieu Lizée, Zhijia Zhang, Baptiste Coquinot et al. (+2 more)
Mechanosensitive ion transport plays a central role in enabling living systems to perceive and adapt to their environment through the deformation of soft, embedded ion channels. In this work, we demonstrate that ion transport within a two-dimensional graphite nanoslit can be rationally engineered to achieve a bipolar, pressure-sensitive response without any structural deformation. The mechanosensitivity arises from the selective charging of one channel inlet, which acts as a reversible source of mobile charge carriers. These excess-ions can then be advected in or out of the channel by the pressure-driven water flow, thereby modulating the ionic conductance. This mechanism is captured through a comprehensive electrohydrodynamic model that analytically accounts for coupled
diffusion, convection, surface transport, diffusio-osmosis, and interfacial slippage, both inside and outside the nanoslit. The theoretical framework quantitatively reproduces the experimental data, showing that a simple surface charge pattern can give rise to complex, pressure-dependent conductance. These findings reveal how rich nonlinear couplings at the nanoscale can be harnessed to design adaptive, bioinspired nanofluidic systems, exemplified here by ionic pressure sensors.
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All authors Mathieu Lizée, Zhijia Zhang, Baptiste Coquinot, Qian Yang, Lydéric Bocquet
Statistical Mechanics
Renormalized entropy production for optimal transport in jump processes: Make conservative forces optimal again
Andreas Dechant and Jann van der Meer
For continuous-space
diffusion processes, there is a strong connection between conservative forces and
entropy production. For a given time
evolution of the system's state, the
entropy production is minimized when the system is driven by a unique conservative force. However, this relation does not extend to jump processes on a discrete state space. In this case, the forces that minimize the
entropy production are generally nonconservative, this effect is more pronounced far from
equilibrium in the presence of high energy barriers. Here we show that, while conservative forces do not minimize the
entropy production for a given time
evolution, they are nevertheless uniquely characterized as the minimizer of a quantity we dub the renormalized
entropy production. This work explores the properties this quantity shares with
entropy production as well as crucial differences between them. We also discuss the conceptual and physical differences between the corresponding optimization problems in finite time. Our theoretical calculations are illustrated with explicit numerical examples.
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Soft Condensed Matter
Dispersion of multiple charged species in an axially symmetric slowly varying channel
Thakurdas Mahata, Anirban Chatterjee and Ameeya Kumar Nayak
The transport and dispersion of multiple species of charged ions are central to many biological and physical processes, including electrokinetic ion separation. However, most theoretical studies of dispersion in channels have focused on neutral solutes, leaving the transport of multiple charged species comparatively unexplored. Differences in ionic diffusivities in a multispecies electrolyte solution generate an self-induced electric fields that drive electromigration. To capture these effects at the macroscopic scale, we combine the lubrication approximation with homogenization theory, under electroneutrality and zero-current constraints, to derive an effective transport equation governing the cross-sectionally averaged concentrations. We apply our model framework to a range of channel geometries and compute the resulting effective dispersion coefficients. Finally, we investigate how channel geometry can be tuned to enhance ionic separation. We observe a geometry-induced electro-diffusive coupling that inhibits solute dispersion in certain channels, leading to a non-monotonic Number of Theoretical Plates (NTP) and making such channels ideal for separation processes.
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Materials Science
Born-Qualified: An Autonomous Framework for Deploying Advanced Energy and Electronic Materials
Steven R. Spurgeon, Milad Abolhasani, Frederick Baddour et al. (+28 more)
Autonomous science is transforming how we discover materials and chemical systems for advanced energy technologies. However, many initially promising systems never reach deployment. This "valley of death" stems from optimization that prioritizes laboratory metrics over industrial viability. We propose a new strategy: "born-qualified" autonomous development, which embeds manufacturability, cost, and durability constraints from the outset. This approach is enabled by four pillars, including the development of multi-objective metrics, causal models, a modular infrastructure, and
embedding manufacturing in the discovery loop. Realizing this
vision will require sustained, community-wide commitment, but the potential return on that investment is commensurate with the scale of the challenge.
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All authors Steven R. Spurgeon, Milad Abolhasani, Frederick Baddour, Ryan B. Comes, Vinayak P. Dravid, Hilary Egan, Patrick Emami, Robert W. Epps, Davi M. Fébba, Renae Gannon, E. Ashley Gaulding, Ayana Ghosh, Kenny Gruchalla, Grace Guinan, Taro Hitosugi, Michael Holden, Sergei V. Kalinin, Yangang Liang, John S. Mangum, Matthew J. Olszta, Nathaniel H. Park, Axel Palmstrom, Michelle A. Smeaton, Brooks Tellekamp, Nicholas E. Thornburg, Raymond R. Unocic, Daniela Ushizima, Rama K. Vasudevan, Robert White, Andrew Young, Andriy Zakutayev