Mesoscale and Nanoscale Physics
Electromotive entrainment of charge and heat currents in graphene
E. Kirkinis, A. Levchenko and A. V. Andreev
We develop a hydrodynamic theory of charge and heat currents induced by traveling waves, such as surface acoustic waves, in
graphene devices near charge neutrality. The currents depend on the intrinsic conductivity and viscosity of the electron
liquid, the disorder strength, and the geometry of the device. We obtain analytic expressions for the heat and charge currents to second order in the wave amplitude for
Hall-bar devices. At charge neutrality and in the absence of DC bias, the heat content is entrained by the wave in the absence of net charge transfer. At the same time, device conductance is enhanced by the wave. Away from charge neutrality, the transport charge current induced by the wave arises in the absence of a DC bias.
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Mesoscale and Nanoscale Physics
Altermagnetic spin textures: Emergent electrodynamics, quantum geometry, and probes
Constantin Schrade and Mathias S. Scheurer
Emergent electrodynamics arising from spatially and temporally varying
magnetic textures provides a framework for
spin control in
quantum materials. While this principle is established for
ferromagnetic and
antiferromagnetic textures, its consequences for altermagnets –
magnetic orders with vanishing net magnetization but finite
spin splitting – remain largely unexplored. In this work, we develop an effective low-energy theory of itinerant electrons coupled to smoothly varying altermagnetic
spin textures. In the adiabatic regime, we show that altermagnetic textures generate additional emergent electromagnetic fields and
quantum-
geometric effects that are absent in conventional
magnetic systems. These effects include emergent Zeeman fields that encode the structure of the altermagnetic order parameter, enabling local
spin manipulation and a way to distinguish different altermagnetic orders. Moreover, we demonstrate a
quantum-metric-induced,
spin-dependent electron
lensing effect that provides a mechanism for
spin filtering, and discuss the local admixture of effective odd-parity
magnetic components. Our results suggest that textured altermagnets could serve as a versatile resource for spintronics functionalities and a probe of altermagnetism.
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Strongly Correlated Electrons · Cross-listed from quant-ph
Generalized $\mathbb{Z}_p$ toric codes as qudit low-density parity-check codes
Zijian Liang and Yu-An Chen
We study two-dimensional translation-invariant CSS stabilizer codes over
prime-dimensional qudits on the square
lattice under twisted boundary conditions, generalizing the Kitaev $\mathbb{Z}_p$ toric code by augmenting each stabilizer with two additional qudits. Using the Laurent-
polynomial formalism, we adapt the Gröbner basis to compute the logical dimension $k$ efficiently, without explicitly constructing large parity-check
matrices. We then perform a systematic search over various stabilizer realizations and
lattice geometries for $p\in\{3,5,7,11\}$, identifying qudit low-density parity-check codes with the optimal finite-size performance. Representative examples include $[[242,10,22]]_3$ and $[[120,6,20]]_{11}$, both achieving $k d^{2}/n=20$. Across the searched regime, the best observed $k d^{2}$ at fixed $n$ increases with $p$, with an empirical relation $k d^{2} = 0.0541 \, n^{2}\ln p + 3.84 \, n$, compatible with a Bravyi–Poulin–Terhal-type tradeoff when the interaction range grows with system size.
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Superconductivity
Jordan T. McCourt, Ryan Henderson, John Chiles et al. (+5 more)
Two-dimensional
superconductors offer an excellent platform for the study of
vortex matter due to their low superfluid stiffness and inability to effectively screen applied
magnetic fields. Here we explore
vortices in a two-dimensional
superconductor formed at the surface of the complex
oxide KTaO$_3$. Multiple regimes of
vortex-mediated transport are identified and studied, revealing switching behaviour attributed to nucleation of individual
vortices. Analysis of this regime allows us to identify the
quantum tunneling of
vortices, which transitions to thermally activated behaviour at elevated temperatures.
Magnetic field dependence reveals rich histograms of the switching currents which we attribute to different configurations of pinned
vortices.
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All authors Jordan T. McCourt, Ryan Henderson, John Chiles, Chun-Chia Chen, Shama, Divine Kumah, Vadim Geshkenbein, Gleb Finkelstein
Materials Science
Role of octahedral tilting induced acoustic softening on limiting thermal transport in SrSnO3
Yuzhou Hao, Turab Lookman, Xiangdong Ding et al. (+2 more)
Octahedral tilting is a fundamental structural distortion in perovskites, governing key phenomena such as
lattice stabilizing, soft
phonon dynamics, group-theoretical analysis, phase transitions, ferroelectricity, and even for tunable electronic band gap. However, its influence on
lattice thermal conductivity (kL) remains poorly understood. In the archetypal perovskite SrTiO3, tilting in the low-temperature tetragonal phase is known to enhance kL by suppressing specific
phonon scattering channels around 200 cm-1. Here, we investigate the thermal transport in strontium stannate (SrSnO3), another perovskite
oxide that undergoes temperature-driven phase transitions, and reveal a completely opposite effect. Through a systematic study across its orthorhombic, tetragonal, and cubic phases, we demonstrate that octahedral tilting in the tetragonal phase of SrSnO3 anomalously triggers acoustic
phonon softening. This softening manifests as reduced frequencies and group velocities in low-frequency (<3 THz) acoustic modes, creating a large decrease for heat transport, particularly along the c-axis. Consequently, kL is significantly suppressed, decreasing from 7.48 W m-1 K-1 to 6.06 W m-1 K-1 as the tilting angle increases by a mere 1 degree. These findings identify tilting-induced acoustic softening as a pivotal mechanism for limiting and controlling anisotropic thermal transport in SrSnO3, presenting a stark contrast to the established behavior in SrTiO3.
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All authors Yuzhou Hao, Turab Lookman, Xiangdong Ding, Jun Sun, Zhibin Gao
Materials Science
Microstructural Evolution and Crystallization Behavior of Amorphous Medium-Entropy Ti-Nb-Zr-Ag Thin Films
Anna Benediktová, Lucie Nedvědová, Michal Procházka et al. (+6 more)
Improving the performance of metallic implants increasingly relies on the development of multifunctional surface modifications that combine structural stability, bioactivity, and prevention of bacterial colonization. Medium-
entropy alloys (MEAs) represent a promising approach for such coatings, as their chemical complexity allows the formation of structurally stable
matrices with tunable properties. In this study, Ti-Nb-Zr and Ti-Nb-Zr-Ag thin films were deposited by magnetron sputtering and subjected to annealing at temperatures of up to 1100 $^{\circ}$C to evaluate the influence of Ag, added for its antibacterial potential, on structural
evolution. The as-deposited Ag-free film was fully amorphous, whereas the Ag-containing film exhibited a predominantly amorphous
matrix with finely dispersed crystalline nanoparticles, indicating that Ag promoted early-stage crystallization. Both films displayed a fine columnar morphology (column diameter $\sim$15 nm) with dome-like protrusions, a hierarchical surface structure favorable for
protein adhesion. Upon annealing, the Ag-free film recrystallized into a granular, loosely packed morphology, while the Ag-containing film retained a compact structure, demonstrating the stabilizing role of Ag. These findings underscore the potential of Ag-containing amorphous MEAs for forming multifunctional coatings with enhanced thermal stability, antibacterial functionality, and biointerface-relevant surface features for advanced biomedical applications.
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All authors Anna Benediktová, Lucie Nedvědová, Michal Procházka, Zdeněk Jansa, Štěpánka Jansová, Christopher D. Woodgate, David Redka, Julie B. Staunton, Ján Minár
Materials Science
Tunable dislocations overcome mechano-functional tradeoff in perovskite oxides
Jiawen Zhang, Wenjun Lu and Xufei Fang
Recent advancements in dislocation engineering are reshaping the traditional view towards ceramics being brittle. Here, we use KTaO3 (KTO), a perovskite
oxide that is newly discovered with room-temperature bulk plasticity, and demonstrate that the seeded dislocations can effectively tune both mechanical and functional properties. We uncover a novel brittle-ductile-brittle (BDB) transition: low dislocation densities lead to brittle failure, intermediate densities (~10*14 m-2) enable superior ductility with strains over 20%, and high dislocation densities (~10*15 m-2) induce again brittle fracture. This dislocation density-dependent non-monotonic mechanical response challenges the traditional behavior of ceramics and offers new design opportunities. Furthermore, dislocation densities can monotonically decrease thermal conductivity, revealing a tradeoff between mechanical strength and functionality. The findings reveal a critical threshold of dislocation density in optimizing the performance of functional
oxides, and provide a new framework for using dislocations to design advanced materials where mechanical durability and enhanced functionality are intertwined.
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Disordered Systems and Neural Networks
Energy gap of quantum spin glasses: a projection quantum Monte Carlo study
L. Brodoloni, G. E. Astrakharchik, S. Giorgini et al. (+1 more)
The performance of
quantum annealing for combinatorial optimization is fundamentally limited by the minimum energy gap $\Delta$ encountered at
quantum phase transitions. We investigate the scaling of $\Delta$ with system size $N$ for two paradigmatic
quantum spin-glass models: the two-dimensional Edwards-Anderson (2D-EA) and the all-to-all Sherrington-Kirkpatrick (SK) models. Utilizing a newly proposed unbiased energy-gap
estimator for continuous-time projection
quantum Monte Carlo simulations, complemented by high-performance sparse
eigenvalue solvers, we characterize the gap distributions across disorder realizations. It is found that, in the 2D-EA case, the inverse-gap distribution develops a fat tail with infinite variance as $N$ increases. This indicates that the unfavorable super-algebraic scaling of $\Delta$, recently reported for binary couplings [Nature 631, 749 (2024)], persists for the Gaussian disorder considered here, pointing to a universal feature of 2D
spin glasses. Conversely, the SK model retains a finite-variance distribution, with the disorder-averaged gap following a rather slow power law, close to $\Delta \propto N^{-1/3}$. This finding provides a promising outlook for the potential efficiency of
quantum annealers for optimization problems with dense connectivity.
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All authors L. Brodoloni, G. E. Astrakharchik, S. Giorgini, S. Pilati
Soft Condensed Matter
Chemotaxis of cell aggregates: morphology and dynamics of migrating active droplets
Giulia L. Celora, Benjamin J. Walker, Mohit P. Dalwadi et al. (+1 more)
Biological tissues have been observed to display emergent fluid-like properties, owing to physical interactions between
cells. However, it remains unclear in general how these fluid-like properties affect tissue structure and function. Here, we are motivated by recent experiments in which
cell aggregates were observed to behave as active droplets during collective migration along chemical gradients, or chemotaxis. To understand this process, we develop a minimal model of a growing thin active droplet driven by a self-generated chemical gradient. In broad agreement with the experiments, dynamic simulations reveal that chemotacting droplets exhibit proliferation-driven morphological transitions. To fully characterise these transitions, we perform a multiple scales analysis to show that the droplet dynamics follow a sequence of travelling wave solutions defined by a nonlinear
eigenvalue problem parametrised by the slowly increasing droplet volume. Our analysis reveals that morphological transitions can occur continuously or through a discontinuous bifurcation. Further asymptotic analysis of the travelling wave problem reveals that these morphological transitions arise from exponentially small ("beyond-all-orders") asymptotic terms that originate from the rear and front contact lines. Moreover, we show that the nature of the transitions is fully determined by two key dimensionless parameters, which quantify the internal stress balance within the droplet and the strength of the coupling between the droplet migration dynamics and the external chemical field. Overall, our results provide a complete characterisation of the morphodynamics of a class of migrating active thin droplets, with implications in a range of biological systems where
cell aggregates exhibit fluid-like behaviour.
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All authors Giulia L. Celora, Benjamin J. Walker, Mohit P. Dalwadi, Philip Pearce
Strongly Correlated Electrons · Cross-listed from quant-ph
Entanglement formation in two-dimensional materials within microcavity
Fabricio Danel Matias, Facundo Arreyes and Juan Sebastián Ardenghi
In this work, the
entanglement generation between two hexagonal-
lattice layers embedded in a microcavity is studied, accounting for both electromagnetic coupling and intrinsic
spin-orbit interaction (SOI). Utilizing a short-time dynamical approach, we perform a perturbative Taylor expansion of the reduced density
matrix to characterize the bipartite
quantum correlations between the hexagonal layers. We demonstrate that the system undergoes a rapid transition from a localized product state in the conduction bands at t = 0 to a coherent superposition of valence and conduction band states. Our results indicate that the degree of
entanglement is highly sensitive to the interlayer
photon propagator, which contains the
geometric ratios of the layer positions and the height cavity, and the specific
Fermi energy and SOI signatures of the respective layers. We show the emergence of spacelike-separated
quantum correlations in the ultra-short
evolution regime, suggesting that
heterostructures in cavities may be suitable to develop experiments for a deep understanding of spacelike-separated
quantum effects.
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Strongly Correlated Electrons
Coexisting magnetic, charge, and superconducting orders in the two-dimensional Hubbard model
Robin Scholle, Pietro M. Bonetti, Walter Metzner et al. (+1 more)
We perform a renormalized mean-field study of the two-dimensional repulsive Hubbard model, focusing on the intricate interplay and possible coexistence of
magnetic, charge, and superconducting orders. We improve on conventional mean-field theory by utilizing a renormalization group framework that captures high-energy fluctuations. This method generates effective
magnetic and $d$-wave pairing interactions, and allows for an unbiased exploration of coexisting phases at weak and moderate interaction strengths. Unrestricted mean-field calculations of the effective
Hamiltonian on large finite
lattices are combined with analyses in the thermodynamic limit, revealing a rich phase diagram with extensive regions of coexisting orders. We find that $d$-wave superconductivity coexists with Néel order on the electron-doped side. On the hole-doped side, superconductivity is found to coexist with spiral or stripe
magnetic orders. Within the stripe ordered region, the superconducting order parameter is spatially modulated, with a period that follows the charge modulation of the stripes. Below van Hove filling, pairing provides the primary energy gain, while the stripe order yields only a small, and hence fragile, additional energy lowering.
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All authors Robin Scholle, Pietro M. Bonetti, Walter Metzner, Demetrio Vilardi
Materials Science
The effect of the A-site cation on the phase transition temperature of metal halide perovskites
Tom Braeckevelt, Sander Vandenhaute, Sven M. J. Rogge et al. (+2 more)
A key challenge for the practical application of metal halide perovskites (MHPs) is the instability of the desired perovskite phase relative to the optically non-active $\delta$ phase. To determine the phase stability, we previously developed a procedure to compute the harmonic free energy as a function of temperature, which was suited for CsPbI$_3$ but fails when Cs is replaced by organic cations due to their rotational freedom. Herein we propose a multistep thermodynamic integration (TI) approach that corrects the harmonic free energy to obtain the Gibbs free energy. Given the abundance of local minima in these materials, we employ replica exchange to prevent simulations from getting trapped, while introducing an intermediate potential energy surface to improve convergence and reduce computational cost. Benchmarking energy and forces from different exchange-correlation functionals and dispersion methods against high-level RPA+HF calculations identifies PBE+D3(BJ) as the best trade-off between accuracy, computational efficiency, and precision. To perform molecular dynamics simulations within the TI framework, it was necessary to train a machine learning potential using the MACE architecture on ab initio data calculated with density functional theory. Our results show that, for all three materials, the free energy difference between the $\gamma$ and $\delta$ phases exhibits a very similar temperature dependence. This suggests that phase stability is primarily governed by differences in ground-state energy, rather than by material-specific thermal effects. Beyond these three materials, our methodology provides a robust framework for investigating the phase behavior of other MHPs, paving the way for the discovery of more stable perovskites.
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All authors Tom Braeckevelt, Sander Vandenhaute, Sven M. J. Rogge, Johan Hofkens, Veronique Van Speybroeck
Materials Science
Cr3+ spin dynamics under the octahedral crystal field in van der Waals antiferromagnets
Rabindra Basnet, Subhashree Chatterjee, Paul Kigaya et al. (+3 more)
The
magnetic moment in van der Waals (vdW) materials containing 3d transition metals originates from unpaired d-electron
spins and their interaction with surrounding ligands. The interplay between exchange interactions and
magnetic anisotropy stabilizes long-range ordering of such moments. The compound CuCrP2S6 (CCPS) presents an interesting class of vdW solids where the coupling of Cr3+ moments and ordering of Cu1+ ions give rise to a multiferroic ground state. Here we investigate the
spin dynamics of Cr3+ ions in CCPS through magnetization and broadband as well as single sub-THz
magnetic resonance measurements. The orbital moment of Cr3+ is quenched under the octahedral
crystal field of surrounding chalcogen ions, resulting in negligible
magnetic anisotropy-a feature common to Cr-based vdW antiferromagnets (AFM). Resonance spectra over a wide frequency-field-temperature range reveal quasi-2D AFM dynamics governed mainly by isotropic Cr-Cr exchange interactions, which determine the
magnetic order,
spin reorientation, and damping. Sub-THz resonance spectra also uncover a field-induced
ferromagnetic polarization, highlighting the universal role of Cr-Cr exchange in layered Cr compounds. Moreover, persistent
magnetic correlations far above the Néel temperature (TN ~ 32 K) points to short-range
magnetic order in CCPS and motivates future studies of a possible interplay between AFM and antiferroelectric orders. These results establish CCPS as an exemplary system for exploring 2D magnetism and electric-field-tunable spintronic functionalities in layered multiferroics.
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All authors Rabindra Basnet, Subhashree Chatterjee, Paul Kigaya, Ezana Negusse, J. van Tol, Ramesh C. Budhani
Soft Condensed Matter
Arc-length characterization of finite, radial growth patterns
Andreas A. Hennig, Ilaria Beechey-Newman, Natalya Kizilova et al. (+1 more)
We present a method to characterize the distribution of length-scales of finite, disordered patterns with, on average, radial
symmetry. This method makes it possible to quantify the distribution of characteristic length scales in cases where the conventional "linear" chord method does not work. We show that the method can clearly distinguish regular patterns, patterns that are formed by
diffusion-limited aggregation, and patterns that form during the slow drying of confined, colloid-laden droplets, explained by Beechey-Newman et al.1 We also introduce a method to find the centre-point of these finite patterns, without assuming a full connectivity in the pattern. The method should be widely applicable to other, finite quasi-two-dimensional patterns like dendritic structures, viscous fingering,
liquid crystal patterns and bacterial growth.
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All authors Andreas A. Hennig, Ilaria Beechey-Newman, Natalya Kizilova, Erika Eiser
Mesoscale and Nanoscale Physics
The interplay of cation/anion and monovalent/divalent selectivity in negatively charged nanopores: local charge inversion and anion leakage
Eszter Lakics, Mónika Valiskó, Dirk Gillespie et al. (+1 more)
The anomalous mole fraction effect (AMFE) is widely regarded as a hallmark of calcium versus monovalent ion selectivity in negatively charged pores. While AMFE is well understood in highly cation-selective narrow ion channels, its microscopic origin in wide synthetic nanopores, where anions may also contribute to transport, remains less clear. Here, we use a reduced Nernst-Planck + Local
Equilibrium Monte Carlo framework to study ionic transport in a negatively charged PET nanopore, with particular emphasis on how the modeling of surface carboxyl (COO$^{-}$) groups influences charge inversion, ionic currents, and AMFE. We systematically compare fixed point-charge models and explicit-particle representations of surface oxygens and identify two controlling parameters: the distance of closest approach (DCA) between ionic charges and pore charges and grid spacing that modulates localization (while keeping average surface charge constant). By fitting pore
diffusion coefficients to three experimental conductance points, we reproduce the entire experimental AMFE curve as well as anion leakage in CaCl$_2$ seen in experiments and molecular dynamics simulations. Remarkably, vastly different microscopic models of the surface groups yield indistinguishable device-level conductance curves when the DCA is matched, despite substantial differences in local Ca$^{2+}$ concentration profiles. Our results demonstrate that AMFE in wide nanopores is governed by a delicate interplay between charge inversion, anion leakage, and ionic mobility, underlying that in wide pores monovalent vs.\ divalent cation selectivity is modulated by cations vs.\ anion selecivity.
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All authors Eszter Lakics, Mónika Valiskó, Dirk Gillespie, Dezső Boda
Strongly Correlated Electrons
Non Fermi liquid signatures across strain engineered metal-insulator transition in line-graph lattices
Shashikant Singh Kunwar and Madhuparna Karmakar
Controlling the properties and thus the functionalities of correlated electron systems via externally tunable perturbations has always remained a cherished goal in
quantum condensed matter physics. Recently, straintronics has proved to be one such external control which can dictate the
quantum phases and transitions in materials via the reconstruction of their electronic band structure. A particularly intriguing scenario arises in the context of flat band line-graph
lattices wherein straintronics is found to bring forth non trivial phase transitions. This paper reports the phase transitions and thermal scales across the Lieb/Kagome interconversion in the electronic interaction-strain-temperature space. Based on the thermodynamic, spectroscopic and transport signatures across the strain tuned interconversion of these line-graph
lattices we have mapped out the low temperature phases and thermal transition scales, numerically determined using non perturbative calculations. While at the low temperatures, interaction-strain plane is spanned by magnetically correlated
insulators, flat band induced weak transiently localized
insulators and non
Fermi liquid metallic phases, thermal fluctuations aid in to stabilize coexistent
magnetic correlations. Apart from quantifying the
magnetic transition scales in this system our results on the spectroscopic and transport signatures distill the strain tuned metal-
insulator transition and crossover scales which exhibit variable transport scaling exponents.
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Materials Science
Electronic structure of Graphene/Co interfaces
Daniela Pacilé, Simone Lisi, Iolanda Di Bernardo et al. (+12 more)
Photoemission, from core levels and valence band, and low-energy electron diffraction (LEED) have been employed to investigate the electronic and structural properties of novel
graphene-
ferromagnetic (G-FM) systems,obtained by intercalation of one mono-layer (1ML) and several layers (4ML) of Co on G grown on Ir(111). Upon intercalation of 1ML of Co, the Co
lattice is resized to match the Ir-Ir
lattice parameter, resulting in a mismatched G/Co/Ir(111) system. The intercalation of further Co layers leads to a relaxation of the Co
lattice and a progressive formation of a commensurate G layer lying on top. We show the C 1s line shape and the band structure of G in the two artificial phases, mismatched and commensurate G/Co, through a comparison with the electronic structure of G grown directly on a Co thick film. Our results show that while the G valence band mainly reflects the hybridization with the d states of Co, regardless of the structural phase, the C 1s line shape is very sensitive to the rumpling of the G layer and the coordination of carbon atoms with the underlying Co. Even in the commensurate (1x1) G/Co phase, where
graphene is in register with the Co film, from the angular dependence of the C 1s core level we infer the presence of a double component, due to in-equivalent adsorption sites of carbon sub-
lattices.
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All authors Daniela Pacilé, Simone Lisi, Iolanda Di Bernardo, M. Papagno, L. Ferrari, Michele Pisarra, Marco Caputo, S. K. Mahatha, P. M. Sheverdyaeva, P. Moras, P. Lacovig, Silvano Lizzit, Alessandro Baraldi, Maria Grazia Betti, Carlo Carbone
Strongly Correlated Electrons
Anisotropic magnons in a layered honeycomb ferromagnet
Travis J. Williams, Douglas L. Abernathy, Mark D. Lumsden et al. (+2 more)
Recent experimental and theoretical studies have suggested a possible Dirac
magnon gap in the two-dimensional
ferromagnetic semiconductor CrSiTe$_3$. Detailed
neutron scattering measurements were performed to shed light on the existence of the
magnon gap, and suggest that the gap is very small or non-existent, with previous measurements being complicated by experimental factors. During these measurements, it was found that the out-of-plane couplings could explain the usual property of the increase in the
magnetic transition temperature when CrSiTe$_3$ is exfoliated to monolayers. Furthermore, the material was shown to have anisotropic
magnons along the out-of-plane direction, through the proposed Dirac point. We speculate that this is due to an exchange anisotropy, though Kitaev-like interactions alone cannot explain the spectra.
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All authors Travis J. Williams, Douglas L. Abernathy, Mark D. Lumsden, Jiaqiang Yan, Andrew D. Christianson
Materials Science
Automated structure discovery for Tip Enhanced Raman Spectroscopy
Harshit Sethi, Markus Junttila, Orlando J Silveira et al. (+1 more)
Tip-Enhanced Raman Spectroscopy (TERS) provides nanoscale chemical fingerprints alongside high-resolution topographic mapping of molecules, offering a powerful tool for materials discovery. However, TERS image
datasets are challenging to interpret and typically demand time-consuming, computationally intensive
quantum-chemistry calculations. To overcome this problem, we present an encoder-decoder model trained and evaluated on simulated TERS images of planar molecules, enabling direct prediction of molecular structures from spectral simulated data with high accuracy. Our approach demonstrates the feasibility of automating molecular structure identification from TERS images, bypassing traditional manual analysis. These findings provide a foundation for extending machine learning methods to experimental TERS
datasets, potentially accelerating molecular discovery by integrating nanoscale spectroscopy with automated computational analysis.
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All authors Harshit Sethi, Markus Junttila, Orlando J Silveira, Adam S Foster
Quantum Gases
Three-dimensional Bose-Fermi droplets at nonzero temperatures
Maciej Lewkowicz, Mirosław Brewczyk, Mariusz Gajda et al. (+1 more)
Using numerical methods, we study the formation of self-bound
quantum Bose-
Fermi droplets at nonzero temperatures. We describe an attractive atomic Bose-
Fermi mixture using
quantum hydrodynamics enriched by beyond-mean-field corrections and thermal fluctuations, together with a simplified self-consistent Hartree-Fock model. With these models, we determine that low-temperature droplets with finite lifetimes can exist in free space when the attraction between
bosons and
fermions is sufficiently strong. Additionally, Bose-
Fermi droplets at nonzero temperatures can exist in a box potential in
equilibrium with bosonic and fermionic vapor. We discuss the properties of Bose-
Fermi droplets at nonzero temperatures in terms of the initial condensate fraction, total atom number, and interspecies attraction strength.
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All authors Maciej Lewkowicz, Mirosław Brewczyk, Mariusz Gajda, Tomasz Karpiuk
Superconductivity
Periodic drive induced unconventional superconductivity in a half-filled system
Suryashekhar Kusari and Arti Garg
The non-
equilibrium control of electronic properties has emerged as a transformative paradigm for engineering novel
quantum phases. The most intriguing example of such a phase is light-induced superconductivity (SC) in non-superconducting materials. However, realizing unconventional SC at commensurate half-filling remains a formidable challenge even in non-
equilibrium, as the regime is typically dominated by the robust stability of the
antiferromagnetic (AFM) Mott insulating (MI) state. Here, we provide a novel non-
equilibrium route to realize unconventional d-wave SC in a half-filled system through Floquet engineering. We analyze the periodically driven
Fermi-Hubbard model on a bipartite
lattice and demonstrate that a high-frequency drive can transform a weakly interacting
insulator into a regime of strong correlations by the drive-induced renormalization of nearest-neighbor hopping. Furthermore, the drive induces staggered higher range hoppings that can frustrate the AFM order while simultaneously generate staggered potential that lifts the kinetic constraints inherent to the half-filled system, fostering the charge dynamics required to stabilize d-wave pairing against the competing AFM state. The resulting SC phase is protected by high-frequency prethermalization, maintaining stability over timescales exponentially large in the drive frequency. This protocol circumvents the need for chemical doping, offering a 'disorder-free' alternative for realizing unconventional pairing with direct applications in optimizing the performance of superconducting
quantum computers,
qubit arrays and other upcoming
quantum technologies.
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Mesoscale and Nanoscale Physics · Cross-listed from quant-ph
Heat flow through the quantum heat valve coupled to ohmic baths via a master equation approach
Antti Vaaranta, Marco Cattaneo, Paolo Muratore-Ginanneschi et al. (+1 more)
We provide a theoretical model for the non-
equilibrium steady state heat flow through a
quantum heat valve. The model is based on a master equation approach, where the partial secular approximation has been carefully performed in order to obtain accurate results. Our study assumes an ohmic spectral density for the two thermal baths of the model. This is in contrast with previous treatments of the
quantum heat valve, where the baths have been assumed as being structured with a peaked spectral density near the resonance frequency of the resonator. These studies have also taken the resonator to be a part of the open
quantum system of interest, which results in double counting of the resonator, as the latter appears both in the spectral density of the bath and as a part of the open system. Although this model accounts for the observations in a satisfactory way, it raises issues regarding its physical interpretation. Our method solves this conceptual problem. We apply it to describe an experiment on a
quantum heat valve, showing that it successfully captures the experimental results and improves upon the previous theoretical model, which suffered from the resonator double-counting issue. Our findings confirm that the careful application of the master equation approach, in particular when it comes to the secular approximation, is a useful tool for explaining realistic experimental setups.
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All authors Antti Vaaranta, Marco Cattaneo, Paolo Muratore-Ginanneschi, Jukka Pekola
Soft Condensed Matter
Mechanical and Structural Contributions to Anisotropy in Granular Materials
Mehdi Pouragha, Gertraud Medicus, Selvarajah Premnath et al. (+1 more)
Anisotropy in granular materials arises from both the internal fabric and the directionality of the stress state, yet separating these effects experimentally remains challenging. This study develops a first-order linearisation of the incremental stress-strain response that isolates mechanical anisotropy from structural anisotropy using two independent orientation measures. The formulation enables both contributions to be quantified directly from macroscopic laboratory data. The method is applied to hollow-cylinder tests with systematically varied loading directions. Results show that both anisotropy components intensify as the stress state becomes more deviatoric; mechanical anisotropy is consistently stronger; and its relative dominance decreases with increasing deviatoric stress. Comparison with an isotropic hypoplastic model confirms that mechanically induced directional effects are captured even without fabric anisotropy. The framework offers a practical and physically transparent means for quantifying and comparing anisotropy mechanisms in granular materials.
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All authors Mehdi Pouragha, Gertraud Medicus, Selvarajah Premnath, Siva Sivathayalan
Soft Condensed Matter · Cross-listed from physics.app-ph
Dielectric response in proteins: The proteotronics approach
E.Alfinito and M. Beccaria
The dielectric properties of
proteins, particularly in their hydrated state, have been extensively studied. Numerous theoretical and experimental investigations have reported values of both the permittivity and the intrinsic dipole moments of specific
proteins under well-defined hydration conditions. Since even approximate estimates of these properties are relevant from both fundamental and applied perspectives, we propose a easy-to-use method to calculate the relative permittivity that can be readily integrated into proteotronics workflows. To validate the proposed approach, we compare the results with those obtained using a classical macroscopic method. The outcomes are consistent and contribute further insight into this long-debated issue.
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Mesoscale and Nanoscale Physics
Quantum-metric-nematicity induced Kerr-like polarization rotation without time-reversal symmetry breaking
Wenhao Liang, Akito Daido and K. T. Law
The magneto-optic Kerr effect (MOKE), which describes the rotation and ellipticity of linearly polarized light upon reflection, is conventionally associated with time-reversal
symmetry breaking. Here, we theoretically demonstrate that a Kerr-like polarization rotation can emerge even in nonmagnetic systems with time-reversal
symmetry, owing to the nontrivial
quantum metric of electronic bands. We show that the nematicity of the
quantum metric, which captures the anisotropy of the
quantum metric tensor due to the breaking of $n$-fold (with $n \ge 3$) rotational
symmetry, gives rise to an incident-polarization-dependent reflected-polarization rotation. Notably, this mechanism requires neither
magnetic order nor
spin-orbit coupling, which are conventionally considered essential for MOKE. We illustrate the effect using a minimal tight-binding model and a model for strained MoS$_2$. This work reveals a
quantum-
geometric origin of the polarization rotation effects beyond conventional MOKE and suggests a new experimental approach to detect
quantum metric nematicity.
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Disordered Systems and Neural Networks · Cross-listed from physics.chem-ph
A Physics-Regularized Neural Network and Kirchhoff Markov Random Field Framework for Inferring Internal Electrochemical States from Operando Spectromicroscopy
Naoki Wada, Yuta Kimura, Masaichiro Mizumaki et al. (+3 more)
Quantitative understanding of coupled reaction-transport dynamics in lithium-ion battery (LIB) composite electrodes is limited by the inaccessibility of key internal electrochemical states. Here we present a physics-integrated, data-driven framework to reconstruct latent states from operando microscopic X-ray absorption fine structure ($\mu$ -XAFS) hyperspectral data of LIB cathodes. Normalized-local-lithium-stoichiometry (NLLS) maps derived from Co K-edge spectra are refined using a physics-regularized neural network that enforces spatial continuity and current conservation to resolve ambiguities in the weak-sensitivity region. The reconstructed NLLS dynamics are embedded in a Kirchhoff-based Markov random field incorporating Kirchhoff's laws, Ohm's law, and Butler-Volmer kinetics to infer interfacial current density, ionic current, electrolyte potential, and effective ionic conductivity. Application to electrodes with differential initial electrolyte concentrations reveals distinct reaction-propagation modes that are consistent with a mechanism involving the non-monotonic concentration dependence of electrolyte conductivity. The inferred electrolyte concentration profiles qualitatively resemble the spatially extended concentration changes observed by independent operando X-ray transmission imaging using a 1 M LiAsF$_6$ electrolyte.
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All authors Naoki Wada, Yuta Kimura, Masaichiro Mizumaki, Koji Amezawa, Ichiro Akai, Toru Aonishi
Quantum Gases · Cross-listed from quant-ph
Rapid state-resolved single-atom imaging of alkaline-earth fermions
Thies Plassmann, Leon Schaefer, Meny Menashes et al. (+1 more)
Local
Hilbert spaces with large dimension are of key interest for
quantum information with applications in
quantum computing and
memories,
quantum simulations and metrology. Thanks to its weak coupling to external perturbations, the large ground-state
nuclear spin manifold of fermionic alkaline-earth atoms is an exciting resource to explore for
quantum information. Simultaneous single atom and state-resolved detection however remains an outstanding challenge limiting the development of novel
quantum computing and simulation schemes beyond
qubits. Here, we report on a new imaging technique enabling the simultaneous detection of up to four
quantum states encoded in the
nuclear spin manifold of a single fermionic strontium atom within 100 microseconds, with state-resolved detection fidelities ranging from 0.936 to 0.997. This technique is further used to track the highly coherent
nuclear spin dynamics after a quench highlighting the potential of this system for
quantum information. These results offer fascinating perspectives for
quantum science with multi-electron atoms ranging from qudit-based
quantum computing to
quantum simulations of the SU(N)
Fermi-Hubbard model.
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All authors Thies Plassmann, Leon Schaefer, Meny Menashes, Guillaume Salomon
Statistical Mechanics
Separation of the Kibble-Zurek Mechanism from Quantum Criticality
R. Jafari and Alireza Akbari
When a system is swept through a
quantum critical point (QCP), the Kibble-Zurek mechanism predicts that the average number of topological defects follows a universal power-law scaling with the ramp time scale. This scaling behavior is determined by the
equilibrium critical exponents of the underlying phase transition. We show that the correspondence between Kibble-Zurek scaling and
quantum criticality does not hold generally. In particular, the defect density can exhibit a suppression faster than the Kibble-Zurek prediction even when the quench crosses a critical point, while conventional Kibble-Zurek scaling may persist for quenches through a non-critical point. Our results, based on models representative of a broad class of quasi-one-dimensional
Fermi systems, identify the dynamical conditions under which universal defect scaling emerges and clarify the relation between defect generation and
equilibrium criticality.
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Soft Condensed Matter
Suppressed Rupture of Thin Metal Films via van der Waals Epitaxy
Wenxiang Wang, Jiaxing Wang, Guotong Wang et al. (+9 more)
Ultrathin metal films exhibit
liquid-like instabilities, rupturing via surface
diffusion far below their melting points. This behavior constrains thermal budgets for advanced integrated
circuits and emerging 2D-
crystal devices. Here, we demonstrate that these instabilities can be fundamentally suppressed using
graphene as a van der Waals (vdW) template. While conventional 20-nm-thick gold films break up into islands below 300 {\textdegree}C, templated films not only remain stable but also become structurally refined after annealing above 600 {\textdegree}C. This exceptional stability stems from a vdW-mediated crystallographic texture that reorganizes grain boundaries into a mechanically robust network. This mechanism significantly widens the processing window for nanoscale interconnects and enables high-temperature integration of metals with 2D-
crystal technologies.
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All authors Wenxiang Wang, Jiaxing Wang, Guotong Wang, Zhichao Yan, Chenxiao Jiang, Siqin Zhou, Chuanli Yu, Jianhao Chen, Kun Zheng, Thomas Salez, Xiaoding Wei, Zhaohe Dai
Quantum Gases · Cross-listed from physics.atom-ph
High-resolution spectroscopy of 162Dy Rydberg levels
G. Ferioli, P. Lombardi, P. Sekhar et al. (+9 more)
Highly excited Rydberg states of lanthanides are a promising, yet largely unexplored, playground for
quantum studies. Here, we report on the first high-resolution spectroscopy of 162Dy obtained by two-color trap depletion spectroscopy in a magneto-optical trap. The absolute excitation frequency of over 700 states with effective principal
quantum number n between 21 and 130 is measured with an accuracy of 20 MHz. Most states are assigned to the 8 different series converging to the first 4f10(5I8)6s(2S1/2) J = 17/2 ionization potential. This energy is measured at EIP = 47901.8265 +/- 0.0008 cm-1, improving the precision of the literature value by over an order of magnitude. A multichannel
quantum defect theory approach is used to
benchmark and refine the assignments and to characterize six observed perturbing states belonging to higher ionization limits. These results pave the way for using dysprosium in Rydberg-based
quantum architectures, leveraging the unique properties arising from its complex electronic structure. They also represent a compelling
benchmark for ab-initio calculations of open-shell atomic systems.
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All authors G. Ferioli, P. Lombardi, P. Sekhar, E. Sole Cardona, N. Preti, C. Drevon, N. Antolini, L. Tanzi, G. Modugno, C. Gabbanini, F. Robicheaux, A. Fioretti