Strongly Correlated Electrons
Non-invertible symmetry enriched string net topological orders
Luisa Eck, Peter Huston, Kyle Kawagoe et al. (+1 more)
We propose a definition of a non-invertible
symmetry enriched topological order (NI-SETO), and we implement our definition for string net models. We do so in two ways, using full inclusions of
unitary fusion categories (UFCs), as well as anyon condensation. In both cases, the NI-SETO is a relative center of UFCs. All NI-SETOs can be realized in either model, where we can use enriched UFCs to get
chiral examples on the boundary of a 3D Walker-Wang model representing the anomaly. We describe several examples of NI-SETOs and compute the qualitative
symmetry action on anyons and
symmetry defects using tube
algebra techniques.
Read the full abstract ▾
All authors Luisa Eck, Peter Huston, Kyle Kawagoe, David Penneys
Mesoscale and Nanoscale Physics
Vectorial Reconstruction of Magnetic Order Parameters using Electron Magnetic Linear Dichroism
Jan Hajduček, Jáchym Štindl, Ján Rusz et al. (+1 more)
Determining the orientation of compensated
magnetic order with nanometer resolution remains a major challenge because conventional
magnetic probes primarily detect net magnetization. Here, we establish electron
magnetic linear dichroism as a quantitative probe of the
spin axis in transmission electron microscopy. Explicit inclusion of vectorial core-level exchange splitting into mixed-dynamic-form-factor simulations accounting for dynamical diffraction enables the calculation of the momentum- and energy-resolved dichroic response for an arbitrary Néel-vector or magnetization orientation. The
magnetic linear contribution can be separated from nonmagnetic anisotropy and exhibits a characteristic angular dependence that enables reconstruction of the
spin axis from a finite set of momentum-resolved electron-energy-loss spectra. Simulations for the
antiferromagnetic and
ferromagnetic phases of cubic FeRh show that this sensitivity persists from parallel illumination to atomically confined probes and over a broad range of
crystal orientations and thicknesses. Electron
magnetic linear dichroism therefore provides a route toward nanoscale vector imaging of compensated
magnetic order in antiferromagnets and related
magnetic materials.
Read the full abstract ▾
All authors Jan Hajduček, Jáchym Štindl, Ján Rusz, Vojtěch Uhlíř
Quantum Gases · Cross-listed from nucl-th
Three-dimensional orbital-free density functional theory description of nuclear pasta in the inner crust of neutron stars
Yo Nakamura and Kazuyuki Sekizawa
Background: In the bottom layer of the inner crust of
neutron stars, various crystalline structures are expected to emerge that are collectively called “
nuclear pasta.” It is desirable to know properties of
nuclear pasta in a wide variety of conditions for astrophysical applications. However, three-dimensional fully-microscopic calculations require huge computational effort that makes it still challenging to carry out systematic calculations. Purpose: In this paper, we propose an efficient method to calculate various
nuclear pasta configurations in a non-empirical manner, based on three-dimensional orbital-free density functional theory (OF-DFT). We demonstrate the feasibility of the proposed approach by applying it to densities across the inner crust of
neutron stars. Methods: As a first application of OF-DFT for
nuclear pasta, we employ the second-order extended Thomas-
Fermi (ETF) expansion of Skyrme energy density functional (EDF) to construct an EDF that depends only on
neutron and
proton number densities. Based on the variational principle, we derive Euler-Lagrange equations to determine optimal
neutron and
proton density distributions and solve them self-consistently. In this work, we call this approach the self-consistent ETF (SC-ETF) method. Results: We perform three-dimensional SC-ETF calculations with various box sizes. We successfully obtain various pasta structures, depending on given average nucleon number densities, consistent with earlier studies. Moreover, we find other exotic structures, such as bending and/or connected rods, slabs with a hole, etc., underlining the advantage of the self-consistent formalism. Conclusions: We demonstrate that the SC-ETF method proposed in this study, which can be regarded as a realization of OF-DFT, is a promising tool that can efficiently describe complex pasta structures without empirical assumptions on
geometric shapes.
Read the full abstract ▾
Strongly Correlated Electrons
Avoided Stoner instability at a single ordinary Van Hove point
I.S. Tupitsyn, B. Currie, A.V. Chubukov et al. (+3 more)
When the
Fermi surface and the Brillouin zone boundary touch at a Van Hove point, mean-field analysis predicts a
ferromagnetic (Stoner) instability at finite $T_{MF}$ for any coupling strength due to the divergent density of states. However, the predicted effect has not been observed experimentally. Several qualitative theoretical proposals have been put forward to explain why the mean-field prediction fails. Based on numerically exact results for the two-dimensional Hubbard model with an ordinary Van Hove singularity, we uncover the mechanisms behind the suppression of the
ferromagnetic instability. We employ two diagrammatic Monte Carlo approaches: (i) the four-channel self-consistent approximation and (ii) numerically exact method of combinatorial summation of diagrams with controlled resummation of the truncated expansion. We find that the system avoids the Stoner instability down to temperatures an order of magnitude below $T_{MF}$ due to the combination of the downward renormalization of the effective coupling and the suppression of the density of states by the loss of the quasiparticle residue.
Read the full abstract ▾
All authors I.S. Tupitsyn, B. Currie, A.V. Chubukov, B.V. Svistunov, E. Kozik, N.V. Prokof'ev
Superconductivity
Absolute measurement of penetration depth of superconducting thin films using microwave stripline resonators
Arghya Dutta, Ajeet Salunke, Mahesh Poojary et al. (+3 more)
Superconducting microstrip resonators, which leverage kinetic inductance to probe electrodynamics, are sensitive tools for studying superconducting thin films at microwave frequencies. However, extracting the absolute superconducting penetration depth from these measurements remains challenging. In this work, we present a hybrid method to determine the absolute value of penetration depth over a wide temperature range by combining resonator measurements with finite-element electromagnetic simulations in COMSOL Multiphysics. We demonstrate this approach by extracting the penetration depth of NbN films by fabricating resonators from films of various thicknesses. Furthermore, we extend the technique to materials with lower critical temperatures by employing a flip-film geometry. By placing a sample above a NbN resonator, separated by a thin Mylar dielectric, we create a coupled structure where changes in the sample's penetration depth shift the resonant frequency. This non-destructive method provides a reliable, high-sensitivity platform for characterizing the penetration depth of diverse superconducting thin films.
Read the full abstract ▾
All authors Arghya Dutta, Ajeet Salunke, Mahesh Poojary, Vivas Bagwe, Sangita Bose, Pratap Raychaudhuri
Materials Science
Universal Stability of Ga Split Vacancies across \alpha-, \beta-, and \kappa-Ga2O3 Polymorphs: A Machine-Learning Accelerated Study
Mohamed Abdelilah Fadla, Myrta Grüning and Lorenzo Stella
Split Ga vacancies are the dominant native acceptor in $\beta$-$Ga_2O_3$; however, their role in $\alpha$ and $\kappa$ phases has been largely overlooked or assumed to be unfavorable. A detailed understanding of these defects is critical for tailoring the electrical conductivity and optical properties and optimising $Ga_2O_3$-based devices. In this work, we used machine learning interatomic potentials (MLIPs) to accelerate the discovery of non-local defect reconstructions, followed by HSE06 hybrid DFT to accurately quantify defect properties of single vacancy $V_{\text{Ga}}$, split vacancy $V_{\text{Ga}}^{\text{i}}$ and substitutional donors ($\mathrm{Hf_{Ga}}$ and $\mathrm{Si_{Ga}}$) across a wide range of experimentally relevant conditions for the oxygen chemical potential. We find that split vacancies are the ground-state vacancy for all studied polymorphs ($\beta$, $\alpha$, and $\kappa$). Split vacancies are more stable than simple vacancies by ~0.75 eV ($\beta$), ~0.41 eV ($\alpha$), and ~0.14 eV ($\kappa$). Notably, MLIPs correctly identified the specific split-vacancy ground states and yielded an energetic ordering of
symmetry-inequivalent defect configurations in excellent agreement with HSE06 results. While Hf and Si show low formation energy and act as shallow donors, especially under oxygen-poor conditions, their efficiency is limited by split-vacancy compensation. The growth under oxygen-poor conditions is a universal requirement to suppress these defects and achieve high n-type conductivity across the $Ga_2O_3$ polymorph.
Read the full abstract ▾
Soft Condensed Matter · Cross-listed from physics.bio-ph
Heatomics
F. Ritort
Living
cells are energy- and information-processing systems that sustain a nonequilibrium steady state (NESS) by continuously consuming energy and dissipating heat, as required by the second law of thermodynamics. The rate of heat dissipation is closely related to the
entropy production rate $\sigma$, a universal primal life signal and unique descriptor of the cellular state. Living matter dissipates $P_{\mathrm{life}} \sim 1$ Watt/kilogram (W/kg), a remarkably conserved value across scales, from molecular reactions to entire organisms. Surprisingly, this high power density is $10^4$ times larger than that of the Sun and comparable to the universe's average, $P_U = c^2 H_0 \sim 1$ W/kg, where $c$ is the speed of light and $H_0$ is Hubble's constant, a striking coincidence reminiscent of Dirac's large number hypothesis. We surmise that this large $P_{\mathrm{life}}$ sets the bar for generating negentropy, which contributes negatively to the overall positive $\sigma$. Negentropy sustains biological organization, distinguishing animate from inanimate matter. Here, I introduce heatomics, the science of studying $\sigma$ at the cellular and molecular scales, and the Variance Sum Rule, an experimental-theoretical framework that extracts $\sigma$ from fluctuations of a dynamical probe combined with the equation of state for a NESS. The emerging field of heatomics aims to elucidate the fundamental principles governing heat power generation, optimization of energy resources, and negentropy in living systems.
Read the full abstract ▾
Quantum Gases · Cross-listed from nucl-th
Formation of bound composite vortices of a singly-quantized $^1$S$_0$ vortex and half-quantized $^3$P$_2$ vortices in the $^1$S$_0$-$^3$P$_2$ coexisting phase in neutron stars
Tatsuhiro Hattori, Muneto Nitta and Kazuyuki Sekizawa
Pulsar glitches are believed to originate from the dynamics of quantized
vortices in the
neutron superfluid interior. The outer core of a
neutron star hosts a $^3\text{P}_2$
spin-triplet superfluid, whose half-integer
quantum vortices (HQVs) are qualitatively different from the $^1\text{S}_0$ singly quantized
vortices (SQVs) in the inner crust. It has recently been proposed that the coupling between these two
vortex species gives rise to a large-scale
vortex network, providing a candidate mechanism for the diversity of observed
pulsar glitch phenomena. Using the Gross–Pitaevskii equations for the $^1\text{S}_0$ and $^3\text{P}_2$ condensates, we perform two-dimensional simulations of one SQV and two HQVs in a coexistence phase near the crust-core boundary, varying the density–density and Josephson coupling constants. We find that the Josephson term, arising from the relative phase between the two condensates, induces a strong attractive interaction between the two HQVs and the SQV, which dominates over the density–density coupling. When pinning potentials are applied to the HQVs and the SQV at spatially separated locations, this attraction is found to be sufficiently strong to drive
vortex depinning. These results suggest that two HQVs and one SQV can form a tightly bound composite
vortex at the crust-core boundary, with implications for the glitch mechanism in
neutron stars.
Read the full abstract ▾
Strongly Correlated Electrons
Odd spin symmetry and anisotropy switching in p-wave magnet CeNiAsO
Fayuan Zhang, Huaxun Li, Xingkai Cheng et al. (+18 more)
Odd-parity magnets, complementary to altermagnets, exhibit unique properties such as high efficiency in charge-
spin conversion and compatibility with conventional superconductivity, of critical importance in the pursuit of energy-efficient spintronics and topological
superconductors for
quantum computation. For even-parity d-wave and g-wave altermagnets, the
magnetic structure,
spin-split band structure and physical properties are currently under intensive study. On the contrary, while hundreds of odd-parity magnets and the promising properties have been predicted in theory, experimental studies are scarce. Specifically, the
magnetic structure and transport properties of candidates NiI2 and Ga3Ru4Al12 have been reported, yet the characteristic band structure and particularly the odd-parity
spin symmetry remain elusive. Here we demonstrate experimentally the deterministic p-wave
spin symmetry and resistance anisotropy switching for the prototype odd-parity magnet, CeNiAsO. Angle-resolved photoemission spectroscopy (ARPES) reveals two cleaved terminations with distinct surface band structure. By compensating the polar surface, we achieve intrinsic bulk band structure, for which the
spin splitting can be well described by the p-wave
magnetic structure through first-principles calculation. The bulk
spin polarization measured by
spin-resolved ARPES exhibits
symmetry with only one degenerate plane, fingerprint of p-wave magnetism. We further demonstrate
giant resistance anisotropy and switching between high-resistance and low-resistance states through modest field-induced domain selection, highlighting its potential for
antiferromagnetic spin memory devices. The structural similarity between CeNiAsO and 1111-type Fe-based
superconductors stimulates further exploration on the interplay between p-wave magnetism, superconductivity and band
topology.
Read the full abstract ▾
All authors Fayuan Zhang, Huaxun Li, Xingkai Cheng, Yibo Fan, Yifan Yin, Yifan Gao, Zhanfeng Liu, Shengtao Cui, Zhouyi Yin, Yue Zhao, Junhao Lin, Zhengtai Liu, Mao Ye, Yaobo Huang, Shan Qiao, Wu Xie, Ping Miao, Hao Wu, Junwei Liu, Guanghan Cao, Chaoyu Chen
Strongly Correlated Electrons
Wolfgang Simeth, Connor A. Occhialini, Michael E. Ziebel et al. (+12 more)
We report
neutron, X-ray absorption, and resonant X-ray spectroscopy of
magnetic excitations in the new heavy-
fermion van-der-Waals
superconductor CeSiI. We determined effective
Hamiltonians and ground states of
crystal electric fields and
magnons. Isotropic Heisenberg interactions on a quasi two dimensional
lattice, including
ferromagnetic nearest-neighbor exchange as the dominant interaction, provide an excellent account to the low-energy measured dynamics and stabilize a co-rotating
spin cycloid. Our study provides the basis to model CeSiI from first principles, thereby laying the ground for microscopic understanding of heavy-
fermion physics, their unconventional superconductivity, and
quantum criticality.
Read the full abstract ▾
All authors Wolfgang Simeth, Connor A. Occhialini, Michael E. Ziebel, Nethmi W. Hewage, Sabrina J. Li, Daniel Pajerowski, Taehun Kim, Ben Zager, Jonathan Pelliciari, Kipton Barros, Daniel Rehn, Abhay N. Pasupathy, Valentina Bisogni, Xavier Roy, Allen Scheie
Strongly Correlated Electrons
Topological lattice gauge theory enriched by non-invertible symmetry
Lea E. Bottini, Clement Delcamp, Edmund Heng et al. (+2 more)
We use finite group topological
lattice gauge theory, also known as the
quantum double model, as a lens to explore a notion of topological order enriched by a non-invertible
symmetry. For invertible
symmetry enriched topological order, there is an established axiomatisation in terms of a G-crossed braided fusion category. We lay the foundations for a generalisation of this notion. By condensing an arbitrary
algebra of charges in a
quantum double model, we demonstrate that the category of localised excitations in the resulting theory forms a hypergroup-graded extension of the category of deconfined excitations. For every element in the hypergroup, the associated domain wall acts in a typically non-invertible way on these localised excitations. Both this action and the monoidal structure are compatible with the hypergroup grading. The actual categorical action is encoded in a
Hopf monad on the category of localised excitations, and gauging the non-invertible
symmetry amounts to computing the category of modules over this
Hopf monad. Finally, we outline how this framework naturally extends to theories obtained by condensing
algebras in a generic string-net model.
Read the full abstract ▾
All authors Lea E. Bottini, Clement Delcamp, Edmund Heng, Campbell K. McLauchlan, Dominic J. Williamson
Materials Science · Cross-listed from physics.optics
Orbital Altermagnetic Photonic Crystal
Sichang Qiu, Huichang Li, Yan Meng et al. (+6 more)
Altermagnetism features momentum-dependent
spin splitting without net magnetization, extending spintronics beyond conventional ferromagnetism and antiferromagnetism. However, the photonic realization of altermagnetism has remained a formidable challenge due to the fundamental differences between fermionic electrons and bosonic
photons. Here, we report the first experimental realization of an orbital altermagnetic photonic
crystal, based on an antiunitary $C_{4z}\mathcal{T}$
symmetry enforced correspondence between a local $p$-orbital $\sigma/\pi$ doublet and
crystal momentum. We experimentally demonstrate that the resulting system exhibits momentum-dependent
spin splitting with alternating pseudospin polarization and a $d_{xy}$-wave form factor, as confirmed by measured band structures and iso-frequency contours. Moreover, we show that the orbital altermagnetic photonic
crystal supports unique pseudospin-selective transport of electromagnetic waves, including photonic pseudospin splitting and pseudospin filtering. Our results extend the field of alternagnetism to photonic systems, opening a new avenue for designing spinphotonic devices.
Read the full abstract ▾
All authors Sichang Qiu, Huichang Li, Yan Meng, Xiang Xi, Zebin Zhu, Ce Shang, Zhen Gao, Tie Jun Cui, Shuo Liu
Soft Condensed Matter
Determinants of Phase-Separation Propensities, Material States, and Material Properties of Biomolecular Condensates
Huan-Xiang Zhou
Phase separation of various materials has been studied for one and a half centuries. In the last two decades, phase separation of
proteins and nucleic acids has received enormous
attention, due its relevance to cellular functions. However, many of the observations on the resulting biomolecular condensates lack a theoretical underpinning. The first goal of this Account is to put forward theoretical frameworks for the phase-separation propensities, material states, and material properties of biomolecular condensates. Using these frameworks, I rationalize mechanistic interpretations from our recent experimental and computational studies, and synthesize these studies with prior literature to draw new conclusions. For phase-separation propensities, I relate the threshold (or saturation) concentration to the excess chemical potential in the dense phase, which in turn depends on intermolecular interaction strength and valency. For material states, I posit that
liquid droplets form via complete phase separation, whereas amorphous dense
liquids, reversible aggregates, and gels arise from premature termination of spinodal decomposition, due to overly weak or overly strong interactions or directional interactions. In particular, gels and aggregates are different forms of dynamically arrested states, with gels driven by tip growth via directional interactions whereas aggregates driven by monomer addition at interior sites to maximize valency. For material properties, I highlight the crucial roles of the stress relaxation time, which is determined by the mean lifetime of intermolecular bonds in a condensate. This relaxation time dictates how the condensate manifests viscoelasticity, including shear thickening and shear thinning, and accounts for the wide variation in zero-shear viscosity among different condensates.
Read the full abstract ▾
Soft Condensed Matter
Geometric Origin of Macroscopic Alignment in Granular Flows
Christopher Harper, Eric C.P. Breard, George W. Bergantz et al. (+1 more)
Predicting the nematic
alignment of nonspherical particles in sheared granular flows is essential for understanding the rheology, packing, and constitutive response of dense particulate media. While macroscopic fabric is typically attributed to complex multibody interactions, stress transmission, and dissipative collisions, empirical observations reveal that the steady-state nematic order parameter $S_2$ depends primarily on particle aspect ratio and remains remarkably insensitive to shear rate and interparticle friction. Here, we show that this leading-order
alignment emerges directly from single-particle boundary geometry without resolving dynamical equations of motion. Assuming uniform contact probability along a particle perimeter, we derive an analytical transform linking local boundary
curvature $\kappa(\theta)$ to the distribution of contact normals, $P(\theta) \propto 1/\kappa(\theta)$, which in turn geometrically constrains the phase space of admissible particle orientations. This minimal framework accurately predicts the magnitude of $S_2$ across the full continuum of aspect ratios for smooth ellipsoids as well as the singular limit of faceted rectangles and cylinders. Our analytical predictions capture the envelope of three-dimensional discrete element simulations and match laboratory measurements on sheared rice grains and glass cylinders across decadal variations in shear rate. By identifying particle geometry as the primary control parameter for granular
alignment, this work provides a first-principles physical foundation for
geometric saturation at the critical state, establishing a universal baseline upon which dynamical and frictional effects act as secondary modulations.
Read the full abstract ▾
All authors Christopher Harper, Eric C.P. Breard, George W. Bergantz, PJ Zrelak
Mesoscale and Nanoscale Physics
Photon correlation microscopy of quantum matter
Elie Vandoolaeghe, Iñigo Lasheras, Chirag Vaswani et al. (+8 more)
Light and matter share fundamental statistical properties, yet the experimental probes of
quantum optics and many-body physics have largely evolved along separate trajectories. While many-body physics explores emergent collective phenomena,
quantum optics has refined the measurement of correlations between individual
photons. Here, we introduce
photon correlation microscopy (PCM) - which bridges the two domains by leveraging correlations of emitted light to probe the correlations in
quantum matter at mesoscopic scales. We demonstrate this approach using a one-dimensional (1D) ensemble of dipolar
excitons confined at a lateral monolayer MoSe$_2$-WSe$_2$ heterojunction. We use gate-defined potentials to confine the 1D
excitons to a mesoscopic lengthscale to enhance the visibility of matter correlations in the emitted
photon field. Power-dependent spectroscopy reveals a transition from a compressible to an incompressible phase, signaled by the simultaneous saturation of the emission intensity and energy blueshift, which is supported by numerical simulations. Through this crossover,
photon correlation measurements show a striking
evolution from bunching at low densities to antibunching at high densities. This constitutes a many-body blockade of
photon emission emerging directly from a number-stabilized state, driven by collective dipolar repulsion. Our results establish PCM as a powerful probe of many-body physics through the lens of
quantum optics, extensible to a broad class of correlated electronic phases, while pointing toward a route to generating non-classical light through many-body correlations.
Read the full abstract ▾
All authors Elie Vandoolaeghe, Iñigo Lasheras, Chirag Vaswani, Sampriti Saha, Purbasha Ray, Takashi Taniguchi, Kenji Watanabe, Prasana Sahoo, Nicolò Defenu, Thibault Chervy, Puneet A. Murthy
Materials Science
Ultrafast dynamics of excitons in black phosphorus
Geoffroy Kremer, Juan F. P. Mosquera, Joël Morf et al. (+9 more)
Excitons are key quasiparticles determining the optical properties of solids. As such, they can be utilized to coherently control the electronic structure of materials using optical femtosecond pulses. Identifying the decoherence mechanism during the early non-
equilibrium dynamics is crucial to achieve light-induced band-structure engineering in
semiconductors. Here, we generate
excitons in the direct band gap
semiconductor black phosphorus with a resonant mid-infrared photoexcitation. Using time- and angle-resolved photoemission spectroscopy, we track their complex ultrafast dynamics on the few-picosecond time scale. We develop a
quantum-kinetic theoretical framework to model the decoherence of
excitons into dark
excitons via
phonon scattering. By combining simulation and experiment, we quantify key parameters describing the early dynamics of the
excitons. Our work highlights
phonon-mediated intravalley scattering as a fundamental limitation for coherent
exciton phenomena in single-valley
semiconductors.
Read the full abstract ▾
All authors Geoffroy Kremer, Juan F. P. Mosquera, Joël Morf, Aymen Mahmoudi, Frédéric Chassot, Viktor Christiansson, Maxime Rumo, Manuele Balestra, Fabian O. von Rohr, Philipp Werner, Michael Schüler, Claude Monney
Quantum Gases
Fractional short-time dynamics in driven quantum gases
Uri Sharell and Tilman Enss
Quantum gases with short-range attractive interaction tend to form pairs. For time-dependent interaction we find that the pairing amplitude at small separation satisfies a fractional differential equation (FDE). We derive analytic solutions of the pairing
evolution for sudden interaction quenches and power-law drives toward resonant scattering. We observe universal short-time dynamics governed by a nonrelativistic conformal fixed point at which the momentum distribution exhibits self-similar dynamic scaling, in quantitative agreement with experiment. At longer times, many-body effects induce relaxation toward an
equilibrium state. In this limit, the FDE turns into a Müller-Israel-Stewart type equation that describes a hydrodynamic attractor approaching
equilibrium.
Read the full abstract ▾
Strongly Correlated Electrons · Cross-listed from quant-ph
Thermodynamic-limit dispersion relations on trapped-ion quantum hardware
Lucas Marti, Sumeet, Stefan Wolf et al. (+2 more)
We run a numerical linked-cluster expansion with a
quantum algorithm (NLCE+QA), computing ground-state energies and one quasi-particle dispersions in the thermodynamic limit using a 20-
qubit trapped-ion
quantum processing unit (QPU). The NLCE+QA framework extracts thermodynamic-limit properties from small-cluster calculations, making it naturally suited for near-term
quantum devices. Projector-based block-diagonalization schemes such as projective cluster-additive transformation (PCAT) are essential to NLCE+QA, and they involve
matrix inversion and square root operations that amplify measurement noise. A central question is therefore whether current hardware can provide expectation values that are accurate enough to withstand non-linear classical post-processing. We explore this challenge for the transverse-field Ising model (TFIM) in one dimension, on a ladder geometry, as well as in a longitudinal field in one dimension. For the
quantum algorithm, we consider adiabatic state preparation (ASP), as well as a variational
quantum eigensolver (VQE) trained on a classical device. The final expectation values are obtained from the QPU, using a novel alternative to the Hadamard test that we name the CX-test. We explore the regimes currently attainable on
quantum devices and comment on the improvements needed for
quantum computers to achieve results beyond classical reach.
Read the full abstract ▾
All authors Lucas Marti, Sumeet, Stefan Wolf, K. P. Schmidt, Michael J. Hartmann
Statistical Mechanics
AI estimation of partition functions with the PULSE method for the thermodynamic properties of disordered compounds
Baptiste Bernard, Luca Messina, Eiji Kawasaki et al. (+1 more)
Predicting the thermodynamic properties of chemically disordered materials is constrained by the combinatorial growth of possible atomic configurations, which makes conventional sampling approaches computationally costly. In this work, we extend the PULSE (Partition function Unsupervised Learning Sampling and Evaluation) approach that enables the estimation of observable-dependent partition functions, thereby extending its applicability from local atomic quantities to general thermodynamic observables. This is based on a generative machine-learning approach in which a single model both generates statistically representative atomic configurations and provides explicit partition function estimates. Our primary goal is to assess it on the two-dimensional Ising model, an exactly solvable
benchmark system sharing the same statistical-mechanical formulation as chemically disordered binary materials, and compare its performance against exact brute-force calculations as well as Wolff and Wang-Landau Monte Carlo
algorithms. PULSE reproduces the relevant partition functions accurately using a limited number of configurations, at a sampling cost that does not grow with system size. These key results demonstrate the relevance of our method to enable the study of disordered materials at scales that are difficult to achieve using conventional approaches, and with limited computational effort.
Read the full abstract ▾
All authors Baptiste Bernard, Luca Messina, Eiji Kawasaki, Emeric Bourasseau
Soft Condensed Matter
Third rank permeability in chiral solids
Roderic S. Lakes
Effects of a third rank permeability term in
chiral solids are studied. Fluid flow through such materials acquires vorticity upon emergence from the material. Materials of interest include
chiral surface
lattices such as the gyroid,
chiral rib
lattices, and granular materials comprised of sugar
crystals, quartz sand, wheat or beans. A characteristic length scale is associated with the chirality. The length scale can be obtained by several methods. Contacts with nonlocal permeability, elasticity and piezoelectricity are explored.
Read the full abstract ▾
Superconductivity · Cross-listed from physics.comp-ph
Surface Contact Approximation for Magneto-Thermal Finite Element Analysis of No-Insulation HTS Coils
Erik Schnaubelt, Louis Denis, Mariusz Wozniak et al. (+2 more)
High-temperature superconducting (HTS) coated conductors (CCs) can be wound into no-insulation (NI) coils, in which electrical current can partially bypass local normal zones via turn-to-turn contact layers (T2TCLs). Accurate magneto-thermal simulation of such coils, therefore, requires an efficient representation of the electrical and thermal behavior of the T2TCLs. This paper introduces a magneto-thermal surface contact approximation (SCA) for finite element analysis of NI HTS coils. The formulation is derived as a special case of the more general thin shell approximation (TSA) by introducing suitable approximations such as negligible tangential surface currents and eddy-current effects inside the T2TCL. The resulting SCA formulation replaces the thin volumetric contact layer with a dedicated surface weak formulation based on the electric contact resistance and thermal contact conductance. In contrast, the TSA formulation requires the definition of electric resistivities and thermal conductivities as well as the thickness of the T2TCL. The SCA is implemented in the Pancake3D module of the free and open-source Finite Element Quench Simulator. It is verified through transient magneto-thermal simulations of a model NI pancake coil. Numerical results are compared against the established TSA formulation. The results show that the SCA accurately reproduces the relevant electromagnetic and thermal behavior. For the TSA, there is a trade-off between choosing large (potentially unphysical) thicknesses with low resistivities leading to inaccurate results, or small thicknesses with large resistivities making the linear system harder to solve, increasing the computational effort. In contrast, the SCA, thanks to using contact resistances and conductances directly without the necessity to define a thickness, is easy to use and robust.
Read the full abstract ▾
All authors Erik Schnaubelt, Louis Denis, Mariusz Wozniak, Julien Dular, Arjan Verweij
Materials Science
Electron-beam induced methane decomposition for in-situ carbon doping of hexagonal boron nitride
Barbara Maria Mayer, Manuel Längle, Umair Javed et al. (+3 more)
Controlling the spatial incorporation of carbon into hexagonal boron nitride (hBN) is essential for engineering optically active defects, yet existing approaches lack nanoscale precision and control over the carbon supply. Here, we demonstrate a method for carbon doping of hBN using electron-beam irradiation in a low-pressure methane atmosphere, where the beam simultaneously generates vacancies and decomposes methane into individual carbon and hydrogen atoms. Using annular dark-field scanning transmission electron microscopy, we show that increasing the methane partial pressure suppresses pore growth and drives the formation of triangular boron-terminated pores through preferential hydrogen etching of nitrogen. Time-resolved electron energy-loss spectroscopy (EELS) mapping reveals progressive carbon incorporation into the
lattice, accompanied by boron and nitrogen depletion. Carbon clustering occurs predominantly within the irradiated area: 84+-7% of carbon-rich regions are confined to the area exposed to the electron beam, while some carbon atoms are also found to diffuse up to an average distance of 4.7+-0.5 nm beyond it. The incorporated carbon atoms arrange in a hexagonal pattern within the
lattice, forming patches that do not exceed ~1 nm in size. Analysis of the EELS fine structure indicates modifications to the local electronic environment within these regions, with implications for the optical properties of the resulting carbon-related defects.
Read the full abstract ▾
All authors Barbara Maria Mayer, Manuel Längle, Umair Javed, Toma Susi, E. Harriet Åhlgren, Jani Kotakoski
Strongly Correlated Electrons
Anisotropic magnetism and Kondo-lattice behavior in the frustrated antiferromagnet Ce3MgBi5
Karolina Gornicka, Brenden R. Ortiz, Matthew S. Cook et al. (+3 more)
We report the synthesis and physical characterization of single-crystalline Ce3MgBi5, a previously unexplored member of the Ce3MPn5 family. This compound crystallizes in the hexagonal P63/mcm structure, featuring an anisotropic Ce sublattice composed of zig-zag chains along the c axis and a distorted kagome-like network in the basal plane. Magnetization measurements reveal
antiferromagnetic order below TN approximately 4.2 K, accompanied by strong
magnetic anisotropy and multiple field-induced metamagnetic transitions for fields applied perpendicular to [001], leading to a dome-shaped H-T phase diagram. Electrical transport exhibits characteristic signatures of a Ce-based Kondo
lattice, including broad resistivity maxima and pronounced field-dependent anomalies in the magnetoresistance and
Hall response that track the
magnetic phase boundaries. Specific-heat measurements confirm the
magnetic transition and show that the full R ln 2
entropy expected for a Ce3+ Kramers doublet is recovered by 20 K, indicating an extended temperature range of
magnetic fluctuations consistent with Kondo correlations. Our results establish Ce3MgBi5 as a platform within the Ce3MPn5 family for exploring the interplay of
geometric frustration,
magnetic anisotropy, and Kondo-
lattice physics under applied
magnetic fields.
Read the full abstract ▾
All authors Karolina Gornicka, Brenden R. Ortiz, Matthew S. Cook, Heda Zhang, Andrew D. Christianson, Andrew F. May
Mesoscale and Nanoscale Physics
Electrically driven Rabi dynamics of magnetic-field-induced corner states in a two-dimensional topological insulator
D. V. Khomitsky, E. A. Lavrukhina, D. P. Krasavin et al. (+2 more)
We study coherent electric manipulation of
magnetic-field-induced localized states at a double kink of a helical edge in a HgTe/CdHgTe
quantum well. An in-plane
magnetic field opens a gap in the one-dimensional edge spectrum, while changes in the edge orientation generate localized in-gap states at the kinks. We show that, for suitable geometry and
magnetic-field direction, two such states form an effective lithographically defined two-level subsystem. Using an edge-state model that includes both the localized levels and the fully propagating 1D edge states outside the
magnetic-field-induced gap, we calculate the electric-dipole
matrix elements and solve the time-dependent problem under resonant driving. The resulting dynamics exhibits Rabi oscillations with linear frequencies of $20$–$40$~GHz for realistic parameters. We find that the propagating 1D edge states provide a leakage channel whose strength is strongly controlled by the driving amplitude: reducing the electric field suppresses leakage below the percent level while preserving GHz-scale coherent oscillations. These results establish a route from
magnetic-field-induced corner-state physics to electrically driven two-level dynamics in a realistic two-dimensional topological-
insulator edge geometry.
Read the full abstract ▾
All authors D. V. Khomitsky, E. A. Lavrukhina, D. P. Krasavin, S. S. Krishtopenko, F. Teppe
Quantum Gases
Wetting of quantum fluids: a route to free-standing shell-shaped quantum droplets
Francesco Ancilotto
We investigate wetting phenomena between self-bound
quantum fluids in a three-component Bose mixture of $^{23}$Na, $^{39}$K, and $^{41}$K atoms. Within a density-functional approach including mean-field interactions and Lee-Huang-Yang
quantum-fluctuation corrections, we consider two binary
quantum liquids, formed by components $(1,2)$ and $(2,3)$, and study the adsorption of the softer $(1,2)$
liquid on a stiffer $(2,3)$ substrate. By tuning the interspecies scattering length $a_{12}$, we show that the surface tension of the $(1,2)$
liquid can be strongly varied, driving a transition from partial wetting to complete wetting of the $(2,3)$ phase. The contact angle extracted from cylindrical-cap geometries decreases continuously with increasing $a_{12}$ and vanishes near a critical value $a_{12}^{c}= -42\,a_0$. In the complete-wetting regime, a finite amount of $(1,2)$
liquid wraps around a spherical $(2,3)$ droplet, producing a self-bound core-shell droplet without external confinement, whose component-1 density has a shell-like, hollow projection. We further show that such shell-shaped
quantum droplets can sustain quantized vortical excitations. These results identify wetting as a route to engineering free-standing shell-shaped
quantum liquids and suggest new possibilities for studying capillarity,
topology, and superfluidity in multicomponent
quantum droplets.
Read the full abstract ▾
Mesoscale and Nanoscale Physics
Substrate-driven topological engineering in plasmonic Su-Schrieffer-Heeger chains
Florian Herz, Alireza Naeimi and Svend-Age Biehs
We demonstrate the possibility of engineering the topological band structure of a plasmonic Su-Schrieffer-Heeger (SSH) chain through the interaction with its electromagnetic environment. We find that the long-range interaction of the in-plane modes of the SSH chain with the surface plasmon polaritons of a planar substrate introduces a band hybridization connected to a change of the Zak phase. On the other hand, the short-range interaction with the substrate introduces a band touching, again with a change in the Zak phase. Surprisingly, this second mechanism enables the emergence of topologically protected edge modes for parameters which correspond to the topologically trivial phase for an isolated plasmonic SSH chain. We study these mechanisms by changing the chain-substrate distance and the dimerization parameter. Finally, we discuss the robustness against disorder and, as one example, the impact of the observed effects on the near-field radiative heat transfer and the local density of states along the chain. Our findings pave the way to the engineering of edge modes in plasmonic topological configurations via the coupling to a plasmonic environment.
Read the full abstract ▾
Statistical Mechanics
The Resetting Heat Engine: A Thermodynamic Cycle of Thermal Expansion and Compression
Oded Farago
We consider a Brownian particle confined by an external potential and subject to
stochastic resetting to the origin. Motivated by the repetitive nature of the dynamics, we describe the process as a thermodynamic cycle of thermal expansion and collapse, analyzed via a framework based on the Kullback-Leibler (KL) divergence between forward and reversed trajectory ensembles. While the
entropy production generally depends on the full trajectory ensemble and cannot be reduced to thermodynamic state variables alone, we show that the harmonic potential constitute a special case, where the
entropy production reduces exactly to a state-function-like expression determined solely by the distributions before and after resetting. Explicit analytical results are derived for periodic and Poissonian resetting. At low resetting rates $r$, the
entropy production rate grows linearly with $r$ and is proportional to the symmetric KL divergence between the reset and
equilibrium distributions. At very high rates, the resetting process becomes effectively perpetual and the
entropy production vanishes. Langevin simulations for an anharmonic quartic potential display the same generic behavior, indicating that these features are not restricted to harmonic confinement. Our results establish a direct connection between
stochastic resetting, thermodynamic cycles, and information-theoretic measures of irreversibility.
Read the full abstract ▾
Mesoscale and Nanoscale Physics
Symmetry-Selective Topological Magnon Engineering by Phonon Angular Momentum
Markus Weißenhofer, Philipp Rieger, Chandan K. Singh et al. (+3 more)
Dynamical control of Berry
curvature remains an outstanding challenge in the engineering of topological phases. Here, we demonstrate control of
magnon band structures via coherently driven
phonons, based on ab initio
spin-
lattice coupling and Floquet theory. We show that this control is
symmetry selective: linearly polarized
phonons leave the spectrum unchanged, whereas circular and elliptical
phonons carrying finite
phonon angular momentum (PAM) induce
chiral interactions that open and tune gaps at Dirac points, generating and reversing topological
magnon phases. The gap magnitude and Chern numbers are directly governed by the PAM, enabling handedness-selective
topology control. Applied to monolayer CrI$_3$, and supported by
symmetry analysis, our results establish driven
lattice dynamics as a general route to engineering topological bosonic excitations and a versatile platform for Floquet control of magnetism.
Read the full abstract ▾
All authors Markus Weißenhofer, Philipp Rieger, Chandan K. Singh, M. S. Mrudul, Sergiy Mankovsky, Peter M. Oppeneer
Materials Science
Can MACE Potentials Accurately Describe Magnetism and Phase Stability in Fe-Ni Alloys? A Systematic Benchmark
Kushal Ramakrishna, Mani Lokamani and Attila Cangi
We present a systematic
benchmark of MACE potentials for iron-nickel
alloys, focusing on structural, elastic,
magnetic, and finite-temperature properties relevant to phase stability. The reference
dataset comprises
spin-polarized PBE density functional theory (DFT) calculations for chemically disordered special quasirandom structures (SQS), spanning compositions, bcc and fcc
crystal structures, and volumetric and shear deformations. A system-specific MACE-sqs model trained on this
dataset achieves validation errors of 2.0 meV/atom for energies and 24.3 meV/Angstrom for forces. Compared with several MACE foundation models, including models trained with Hubbard U corrections, MACE-sqs gives the most consistent agreement with DFT and experiment for equations of state,
equilibrium volumes, elastic constants, and thermal expansion trends in bcc and fcc Fe-Ni
alloys. For the bcc-to-hcp transition, MACE-sqs predicts a pure-Fe transition pressure closer to experiment than the tested foundation models, but all models predict an incorrect increase of transition pressure with Ni content. This failure indicates that high-pressure
magnetic collapse and composition-dependent magnetoelastic effects are not yet fully captured. Overall, targeted SQS-based training substantially improves the accuracy of MACE potentials for Fe-Ni
alloys, while phase stability under
magnetic collapse remains a key limitation for future model development.
Read the full abstract ▾
Materials Science
Global magnetic phase diagram and multiple unconventional magnets in NiAs-type compounds
Shibo Shen and Yilin Wang
NiAs-type compounds such as CrSb and MnTe host $g$-wave altermagnet (AM) state. In order to search other possible unconventional magnets in this system, we present a global
magnetic phase diagram based on a classical $J_1$-$J_2$-$J_3$ Heisenberg model and density functional theory (DFT) calculations. We find another $g$-wave AM state and two $f$-wave OPMs in the phase diagram. Intriguingly, we show that a mixed-parity of the $f$-wave OPM and $g$-wave AM state can naturally emerge in an umbrella-like noncollinear
magnetic structure. Our DFT calculations show that CrSe and CrTe$_{1-x}$Se$_x$ are generally in such mixing state with dominated $f$-wave component. The interlayer next-nearest-neighbor coupling $J_3$ is shown to be crucial in determining the phase diagram and in inducing strong competition between conventional and unconventional magnets. Inspired by this, we demonstrate that AM or OPM could be realized by applying chemical doping or strain to conventional magnets. Our results provide a guidance for design of both even- and odd-parity as well as mixed-parity unconventional magnets in NiAs-type compounds.
Read the full abstract ▾