Materials Science
Escape-Induced Temporally Correlated Noise Driven Universality Crossover
Mrinal Manna, Sourav Mukherjee, Soumen Giri et al. (+11 more)
Universal behavior in far-from-
equilibrium systems is driven by interactions between transport processes and noise structure. The Kardar-Parisi-Zhang (KPZ) framework predicts that extensions incorporating conserved currents or temporally correlated noise give rise to distinct growth morphologies and universality classes, yet direct experimental realization has remained elusive. Here, we report atomically resolved Sn thin-film growth on Sb-doped MnBi$_2$Te$_4$, revealing a sharp dynamical crossover between two fundamentally different regimes. Early stage growth follows conserved KPZ scaling, forming two-dimensional islands and stanene layers. Beyond a critical deposition time, temporally correlated noise dominates, driving the nucleation of $\alpha$ -Sn clusters, their
evolution into faceted grains, and coexistence with faceted $\beta$-Sn. Molecular dynamics simulation and Auger electron spectroscopy show adatom escape as the microscopic origin of temporally correlated noise, providing a microscopic mechanism for the universality crossover. These findings establish, for the first time, that temporal noise correlations can fundamentally alter the scaling class of a growing interface, linking atomistic kinetics to emergent universal behavior.
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All authors Mrinal Manna, Sourav Mukherjee, Soumen Giri, Pramod Bhakuni, Sajal Barman, Arnab Kumar Pariari, Anil Gome, Markus Hucker, V. Raghavendra Reddy, Anupam Roy, Sudipta Roy Barman, Smarajit Karmakar, Chandana Mondal, Rajib Batabyal
Soft Condensed Matter
Anonymous leadership and stochastic resonance in collectives of self-propelled robots
Manuel Dizenhaus, Franco De Simone and German A. Patterson
We investigate the influence of an anonymous leader on a collective of self-propelled
robots using Kilobot experiments and numerical simulations. A single leader alternated deterministically between clockwise and counterclockwise motion, while the other
robots followed a
stochastic majority rule. Although the leader does not change global order, it induces correlations with the collective response that peak at intermediate perturbation levels, resembling
stochastic resonance. Simulations confirm that this resonance occurs when the leader's reversal period matches the mean residence time of the unperturbed system. Our results contribute to understanding decision-making in active matter and suggesting principles for steering robotic swarms with minimal leadership input.
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Quantum Gases · Cross-listed from nucl-th
Transport properties of stochastic fluids
Chandrodoy Chattopadhyay, Josh Ott, Thomas Schaefer et al. (+1 more)
We study heat conduction and momentum transport in the context of
stochastic fluid dynamics. We consider a fluid described by model H in the classification of Hohenberg and Halperin. We study both non-critical and critical fluids, and we investigate transport properties in two as well as three dimensions. Our results are based on numerical simulations of model H using a Metropolis
algorithm, and we employ Kubo relations to extract transport coefficients. We observe the expected logarithmic divergence of the shear viscosity in a two-dimensional non-critical fluid. At a critical point, we find that the transport coefficients exhibit power-law scaling with the system size $L$. The strongest divergence is seen for the thermal conductivity $\kappa$ in two dimensions. We find $\kappa\sim L^{x_\kappa}$ with $x_\kappa=1.6\pm 0.1$. The divergence is weaker in three dimensions, $x_\kappa=1.25 \pm 0.3$, and the scaling exponent for the shear viscosity, $x_\eta$, is significantly smaller than $x_\kappa$ in both two and three dimensions.
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All authors Chandrodoy Chattopadhyay, Josh Ott, Thomas Schaefer, Vladimir V. Skokov
Mesoscale and Nanoscale Physics
Conductance Plateaus at Quantum Hall Integer Filling Factors in Germanium Quantum Point Contacts
Karina Hudson, Davide Costa, Davide Degli Esposti et al. (+2 more)
Constricting transport through a one-dimensional
quantum point contact in the
quantum Hall regime enables gate-tunable selection of the edge modes propagating between voltage probe electrodes. Here we investigate the
quantum Hall effect in a
quantum point contact fabricated on low disorder strained germanium
quantum wells. For increasing
magnetic field, we observe Zeeman
spin-split 1D ballistic hole transport evolving to integer
quantum Hall states, with well-defined quantised conductance increasing in multiples of $e^2/h$ down to the first integer filling factor $\nu=1$. These results establish strained germanium as a viable platform for complex experiments probing many-body states and
quantum phase transitions.
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All authors Karina Hudson, Davide Costa, Davide Degli Esposti, Lucas E. A. Stehouwer, Giordano Scappucci
Statistical Mechanics · Cross-listed from nlin.CD
Spatiotemporal stability of synchronized coupled map lattice states
Domenico Lippolis
In the realm of spatiotemporal chaos, unstable periodic orbits play a major role in understanding the dynamics. Their stability changes and bifurcations in general are thus of central interest. Here, coupled map
lattice discretizations of nonlinear partial differential equations, exhibiting a variety of behaviors depending on the coupling strength, are considered. In particular, the linear stability analysis of synchronized states is performed by evaluating the Bravais
lattice orbit Jacobian in its reciprocal space first Brillouin zone, with space and time treated on equal grounds. The
eigenvalues of the orbit Jacobian operator, computed as functions of the coupling strength, tell us about the stability of the periodic orbit under a perturbation of a certain time- and space frequency. Moreover, the stability under aperiodic, that is, incoherent perturbations, is revealed by integrating the sum of the stability exponents over all space-time frequencies.
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Mesoscale and Nanoscale Physics
Origin of Enhanced Thermal Resistance Near Nanoscale Hotspots: Insights from Full-Dispersion-Resolved Phonon Transport in Silicon
Jae Sik Jin
Phonon transport near nanoscale hotspots (NHs) critically determines heat dissipation in advanced electronic devices. The prevailing understanding is that the enhanced thermal resistance (TR) observed in NHs originates from long mean free path (MFP)
phonons, whose MFPs are much larger than the hotspot size, thereby limiting their ability to recognize hotspots and transport heat effectively. In this study, we revisit this problem by employing the Boltzmann transport equation (BTE) with a full
phonon dispersion model (FPDM) to capture mode-resolved velocities, scattering processes, and nonequilibrium
phonon populations in silicon. The analysis demonstrates that the increase in TR near NHs is not caused by the long MFP itself but by the low specific heat of long-MFP
phonons that do not scatter directly with optical modes. These
phonons heat readily when energy is supplied, steepening the local temperature gradient near the NH and thereby enhancing TR. By resolving the spectral contributions to the
phonon transport resistance and temperature gradients, we identify the critical role of the modal specific heat in nonlocal
phonon transport. These results provide new physical insights into nanoscale thermal management and highlight the importance of spectral mode resolution in modeling heat dissipation in electronic devices.
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Materials Science
Anharmonic Effects in Ge2Sb2Te5 and Consequences on Thermodynamic Stability
Owain T. Beynon and Adham Hashibon
Chalcogenides are an important class of phase change material (PCMs) due to their application in digital
memory solutions. Owing to their ability to reversibly cycle between crystalline and amorphous states, their use as phase change random access
memory (PCRAM) is of interest, and of the many chalcogenide materials Ge2Sb2Te5 (GST) is a promising candidate owing to its stability and low crystallization temperature. GST possesses two stable crystalline polymorphs, cubic and hexagonal. Studies show that phenomena such as heat transport and thermal
lattice expansion drive the phase-change nature of these materials. These phenomena are not incorporated in the harmonic approximation, which is a popular model for describing vibrations in solids. Through ab initio density functional theory (DFT), we computationally investigate the anharmonic behaviour of pristine hexagonal GST, i.e. without vacancies or defects, while considering the various stacking models that exist and inclusion of van der Waals (vdW) interactions in our modelling. We present the vibrational analysis of different stacking models in GST; Petrov and Kooi-De Hosson (KDH) models and the quantification anharmonic behaviour. Our calculations find that the KDH model is the most stable stacking sequence, being 88 meV more stable than the Petrov model when considering anharmonicity, where this difference is underestimated using a purely harmonic framework (65 meV). These results demonstrate the importance of incorporating anharmonic and dispersion effects when modelling GST, especially in the choice of stacking models, along with implications for phenomena relating to phase-change behaviour.
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Statistical Mechanics · Cross-listed from quant-ph
Semiclassical analytical solutions of the eigenstate thermalization hypothesis in a quantum billiard
Yaoqi Ye, Chengkai Lin and Xiao Wang
We derive semiclassical analytical solutions for both the diagonal and off-diagonal functions in the eigenstate thermalization hypothesis (ETH) in a quarter-stadium
quantum billiard. For a representative observable, we obtain an explicit expression and an asymptotic closed-form solution that naturally separate into a local contribution and a phase-space correlation term. These analytical results predict the band structure of the observable
matrix, including its bandwidth and scaling behavior. We further demonstrate that our analytical formula is equivalent to the prediction of Berry's
conjecture. Supported by numerical evidence, we show that Berry's
conjecture captures the energetic long-wavelength behavior in the space of eigenstates, while our analytical solution describes the asymptotic behavior of the f function in the semiclassical limit. Finally, by revealing the connection between the bandwidth scaling and the underlying classical dynamics, our results suggest that the ETH carries important physical implications in single-particle and few-body systems, where "thermalization" manifests as the loss of information about initial conditions.
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Mesoscale and Nanoscale Physics
Green's function expansion for multiple coupled optical resonators with finite retardation using quasinormal modes
Robert Meiners Fuchs, Juanjuan Ren, Stephen Hughes et al. (+1 more)
The electromagnetic Green's function is a crucial ingredient for the theoretical study of modern photonic
quantum devices, but is often difficult or even impossible to calculate directly. We present a numerically efficient framework for calculating the scattered electromagnetic Green's function of a multi-cavity system with spatially separated open cavities (with arbitrary shape, dispersion and loss) and finite retardation times. The framework is based on a Dyson scattering equation that enables the construction of the Green's function from the quasinormal modes of the individual resonators within a few-mode approximation and a finite number of iteration steps without requiring nested integrals. The approach shows excellent agreement with the full numerical Green's function for the example of two coupled dipoles located in the gaps of two metal dimers serving as quasinormal mode cavities, and is easily extended to arbitrarily large separations and multiple cavities.
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All authors Robert Meiners Fuchs, Juanjuan Ren, Stephen Hughes, Marten Richter
Statistical Mechanics · Cross-listed from physics.flu-dyn
Hydrodynamic Ratchet for Tracer Transport in a Soft Microchannel: A Detailed Analysis
Aakash Anand and A. Bhattacharyay
Understanding surface-driven transport is of paramount importance from the perspective of biological applications and the synthesis of microfluidic devices. In this work, we develop an analysis of a local inversion
symmetry broken fluid flow model through an undulating microchannel. Surface undulations of a few tens of Hertz in a soft microchannel keep the fluid flow in a low Reynolds number regime, allowing the advantage of a perturbation analysis of fluid flow. Using this, we develop a detailed analysis of the relationship between the fluid velocity and surface undulations, which is crucial for the subsequent numerical analysis of tracer motion. We used this information to study the dynamics of a tracer particle in the velocity field of an undulating microchannel. We show that the tracer particle can undergo ratcheting (which we call the hydrodynamics ratchet effect) in very specific, physically meaningful circumstances. We observe a ratcheting velocity of $\sim 0.15 \;\mu$m/sec for a micrometre-sized particle at room temperature in water when the undulations wavelength is of the order of 1 $\mu$m.
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Materials Science
Two-Dimensional Na2LiAlP2 Crystal for High-Performance Field-Effect Transistors
Run-Jie Peng, Xing-Yu Wang, Jun-Hui Yuan et al. (+4 more)
High-performance, low-power transistors are core components of advanced integrated
circuits, and the ultimate limitation of Moore's law has made the search for new alternative pathways an urgent priority. Two-dimensional (2D) materials have become the most promising exploration target due to their exceptional electronic properties and scalability. In this work, we conducted device transport research on the previously proposed 2D quaternary
semiconductor Na2LiAlP2 using the non-
equilibrium Green's function method. The results demonstrate that even with a channel length of 5 nm, Na2LiAlP2 still exhibits excellent n-type transistor characteristics, fully meeting and surpassing the technical specifications outlined in the International Roadmap for Devices and Systems (IRDS). Encouragingly, the device can easily achieve the required on-state current of 900 {\mu}A/{\mu}m under low operating voltages of 0.1 V and 0.2 V. Moreover, at 0.1 V operating voltage, the device's subthreshold swing breaks through the theoretical limit of 60 mV/dec, reaching an astonishing value 30.33 mV/dec. Additionally, its p-type transistor performance also stands out with a subthreshold swing of ~50 mV/dec when the channel length is 7 nm. Our research not only showcases the exceptional transistor properties of Na2LiAlP2 but also further expands the research scope of 2D high-performance transistors.
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All authors Run-Jie Peng, Xing-Yu Wang, Jun-Hui Yuan, Nian-Nian Yu, Kan-Hao Xue, Jiafu Wang, Pan Zhang
Superconductivity
Possible high-Tc superconductivity at 45 K in the Ge-doped cluster Mott insulator GaNb4Se8
Ji-Hai Yuan, Ya-Dong Gu, Yun-Qing Shi et al. (+8 more)
The Ge-doped GaNb4Se8 polycrystalline samples were synthesized by solid-state reaction method. Zero resistance transitions were observed in one batch of samples with the highest onset superconducting Tc at 45 K. This discovery may demonstrate a new class of Nb-based high-Tc
superconductors arising from doped Mott
insulators.
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All authors Ji-Hai Yuan, Ya-Dong Gu, Yun-Qing Shi, Hao-Yu He, Qing-Song Liu, Jun-Kun Yi, Le-Wei Chen, Zheng-Xin Lin, Jia-Sheng Liu, Meng Wang, Zhi-An Ren
Materials Science
Self-attention enabled quantum path analysis of high-harmonic generation in solids
Cong Zhao and Xiaozhou Zou
High-harmonic generation (HHG) in solids provides a powerful platform to probe ultrafast electron dynamics and interband–intraband coupling. However, disentangling the complex many-body contributions in the HHG spectrum remains challenging. Here we introduce a machine-learning approach based on a
Transformer encoder to analyze and reconstruct HHG signals computed from a one-dimensional Kronig–Penney model. The self-
attention mechanism inherently highlights correlations between temporal dipole dynamics and high-frequency spectral components, allowing us to identify signatures of nonadiabatic band coupling that are otherwise obscured in standard
Fourier analysis. By combining
attention maps with Gabor time–frequency analysis, we extract and amplify weak coupling channels that contribute to even-order harmonics and anomalous spectral features. Our results demonstrate that multi-head self-
attention acts as a selective filter for strong-coupling events in the time domain, enabling a physics-informed interpretation of high-dimensional
quantum dynamics. This work establishes
Transformer-based
attention as a versatile tool for solid-state strong-field physics, opening new possibilities for interpretable machine learning in attosecond spectroscopy and nonlinear photonics.
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Materials Science
Defect Passivation and Förster-Type Energy Exchange in H2Pc-TMD Organic-Inorganic Heterostructures
Šimun Mandić, Ana Senkić and Nataša Vujičić
Organic - inorganic
heterostructures (HS) combine the strong light absorption and
exciton generation capabilities of organic molecules with the unique excitonic properties of layered transition metal dichalcogenides (TMDs), where the interfacial band
alignment dictates the optical response. In this work, we investigate the influence of H2Pc molecules on CVD-grown MoS2 and WS2 monolayers using correlative microscopy techniques - Kelvin probe force microscopy (KPFM), photoluminescence (PL), and Raman spectroscopy. Comprehensive analysis of both electronic and optical properties provides detailed insights into the energy band
alignment in these two HS. Despite their similar band
alignments, the
heterostructures exhibit strikingly different optical signatures. In the case of H2Pc/MoS2 HS, the effect of defect healing is more pronounced, while for the H2Pc/WS2 HS, strong indications of Förster energy transfer are observed. These findings highlight the critical role of transition dipole moment in addition to spectral overlap between donor emission and acceptor absorption in the design of optoelectronic devices.
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Materials Science · Cross-listed from cs.LG
Continuous SUN (Stable, Unique, and Novel) Metric for Generative Modeling of Inorganic Crystals
Masahiro Negishi, Hyunsoo Park, Kinga O. Mastej et al. (+1 more)
To address pressing scientific challenges such as
climate change, increasingly sophisticated generative models are being developed to efficiently sample the large chemical space of potential functional materials. The proliferation of these models has necessitated the establishment of rigorous evaluation metrics. While uniqueness (U), novelty (N), and stability (S) of samples serve as standard metrics, their current formulations show several limitations. U and N rely on binary comparisons of
crystals, rendering them dependent on heuristic thresholds, incapable of quantifying the degree of similarity, sensitive to atomic coordinate perturbations, and not invariant to sample permutation. Similarly, the binary assessment of S risks a premature exclusion of marginally unstable yet potentially novel candidates. These limitations are addressed by making the aforementioned metrics continuous. Furthermore, we integrate them into a unified metric “continuous SUN" (cSUN), which offers a smoother score distribution and greater tunability than the conventional binary SUN metric. Experimental results demonstrate that our continuous metrics provide granular insights into sample distributions and secondarily serve as a soft screening score for selecting samples for further analysis. Finally, the use of cSUN as a reward signal in reinforcement learning is explored, showing that its adjustable weighting scheme effectively enhances sample diversity and convergence to a better optima in a Chemeleon2 case study.
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All authors Masahiro Negishi, Hyunsoo Park, Kinga O. Mastej, Aron Walsh
Quantum Gases
Empty and filled vortices in squeezed 39K Bose-Bose liquid drops
Ivan Poparić, Leandra Vranješ Markić and Jordi Boronat
Using density functional theory, we have theoretically studied the formation and the stability of
vortices in
quantum liquid droplets composed of a mixture of hyperfine states of potassium. Following the experimental setup that produced
quantum droplets for the first time, we work with squeezed drops that are compressed in one direction. By squeezing the drops even more, towards a quasi-two dimensional geometry, we study the minimum atom number able to show a stable
vortex and obtain that this number is significantly smaller than previous predictions for spherical droplets. The reduction of the critical atom number for forming a stable
vortex could make their experimental observation in these droplets, which is still lacking, more feasible. Contrary to results obtained in heteronuclear mixtures, where the energetically preferred
vortices are partially filled with the species not participating in the rotation, our results show a relevant stability island of fully empty
vortices. Increasing the number of particles in the drop and the speed of rotation, we estimate the transition line between empty and filled
vortices.
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Materials Science
Controlling Magnetism in the 2D van der Waals Antiferromagnet CrPS$_4$ via Ion Intercalation
Alberto M. Ruiz, Diego López-Alcalá, Gonzalo Rivero-Carracedo et al. (+2 more)
Two-dimensional van der Waals (vdW)
magnetic materials are versatile platforms for tailoring electronic and
magnetic properties, in which the insertion of chemical species into their interlayer gaps offers a powerful route to engineer magnetism. Here, we focus on the A-type
antiferromagnetic semiconductor CrPS$_4$ (T$_N$ = 38 K) and investigate its electronic and
magnetic properties upon intercalation of lithium (Li$^+$) and organic tetrabutylammonium (TBA$^+$) ions using first-principles calculations. Our results show that Li$^+$ incorporation induces a
semiconductor-to-metal transition in CrPS$_4$ and selectively modifies its
magnetic behaviour: switching from out-of-plane to in-plane antiferromagnetism, followed by an in-plane
ferromagnetic ground state at higher intercalation levels. This is accompanied by a continuous increase of the ordering temperature, reaching a fivefold enhancement for Li$_{0.5}$CrPS$_4$. Similarly, TBA$^+$ intercalation expands the vdW gap, decoupling CrPS$_4$ layers and stabilising in-plane ferromagnetism with a T$_C$ above 100 K. Furthermore, it also modifies
magnon propagation, leading to enhanced group velocities and a more isotropic
magnon transport. This work highlights intercalation as a powerful and versatile approach for controlling
magnetic behaviour and
spin dynamics, paving the way for the design of tunable 2D layered
magnetic materials for spintronic and magnonic applications.
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All authors Alberto M. Ruiz, Diego López-Alcalá, Gonzalo Rivero-Carracedo, Andrei Shumilin, José J. Baldoví
Other Condensed Matter
Investigating the relationship between the Weyl semimetal phase and the three-dimensional quantum Hall phase in ZrTe$_5$
Jiahao Chen, Yu Cao, Hong Du et al. (+3 more)
The material ZrTe$_5$ exhibits distinct topological phases, including a Weyl semimetal phase, characterized by a
chiral anomaly and in-plane
Hall effect, and a three-dimensional
quantum Hall phase. The relationship between these phases remains poorly understood. This work systematically explores their connection in ZrTe$_5$ through rotatable, pressure-dependent measurements. At ambient pressure, both phases are observed; the WSM phase requires strong electronic polarization, while the 3D QH phase appears when the characteristic resistivity peak temperature $T_p$ is approximately 90 K. Under applied pressure, the polarization diminishes, weakening the WSM phase and its associated nontrivial
Hall signals. Concurrently, $T_p$ rises dramatically from 2 K at ambient pressure to 70 K at 2.2 GPa, approaching the expected regime for the 3D QH phase. These findings clarify the conditions underlying the WSM and 3D QH phases and suggest that exploring the 3D QH phase at even higher pressures is a promising direction for future research.
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All authors Jiahao Chen, Yu Cao, Hong Du, Yuanze Li, Ruidan Zhong, Tian Liang
Superconductivity
Interlayer coupling enhanced superconductivity near 100 K in La$_{3-x}$Nd$_x$Ni$_2$O$_7$
Zhengyang Qiu, Junfeng Chen, Dmitrii V. Semenok et al. (+12 more)
Systematically controlling the superconducting transition temperature ($T_\text{c}$) in the
bilayer Ruddlesden-Popper nickelate La$_3$Ni$_2$O$_7$ remains a significant challenge. Here, we address this by synthesizing high-quality polycrystalline La$_{3-x}$Nd$_x$Ni$_2$O$_7$ ($0 \leq x \leq 2.4$) with record-level rare-earth substitution. Nd doping compresses the
lattice, particularly along the $c$ axis, enhances the
spin density wave transition temperature, and elevates the pressure required for the orthorhombic-to-tetragonal structural transition. Superconductivity is observed across all doping levels under high pressures, with the onset $T_\text{c}$ rising to $\sim$93~K for $x = 2.1$ and $2.4$ from the electronic transport measurement. Using the
radio-frequency transmission technique, newly applied to nickelate
superconductors, we detect signatures of superconductivity at $98 \pm 2$~K in the $x=2.4$ compound, pushing the $T_\text{c}$ frontier further. We identify a universal linear relationship where $T_\text{c}$ decreases with the $c$-axis
lattice parameter at a rate of approximately $-28$~K/Å, demonstrating that enhanced interlayer
magnetic exchange coupling is the dominant mechanism for superconducting pairing. Our work establishes the critical role of magnetism and provides a unified structural descriptor for elevating $T_\text{c}$ in
bilayer nickelates.
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All authors Zhengyang Qiu, Junfeng Chen, Dmitrii V. Semenok, Qingyi Zhong, Di Zhou, Jingyuan Li, Peiyue Ma, Xing Huang, Mengwu Huo, Tao Xie, Xiang Chen, Ho-kwang Mao, Viktor Struzhkin, Hualei Sun, Meng Wang
Strongly Correlated Electrons
$\eta$-pairing in the model with two-particle hybridization of conduction and localized electrons
Igor N. Karnaukhov
Within the framework of a model, that takes into account two-particle hybridization of conduction and localized electrons, the effective interaction between conduction electrons is calculated. It is shown that this interaction is attractive when the energy of the localized electron corresponding to the two-particle state lies in the conduction band above the
Fermi energy. The magnitude of the attractive interaction is minimal for $\eta$-paired states of conduction electrons. We generalize the original $\eta$-pairing construction for the proposed model and show that the superconducting state can indeed be realized.
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Materials Science
Two-Dimensional Altermagnetism in Epitaxial CrSb Ultrathin Films
Keren Li, Yuzhong Hu, Yue Li et al. (+12 more)
Altermagnets constitute an emerging class of collinear magnets that exhibit zero net magnetization yet host
spin-split electronic bands arising from non-relativistic
spin-space-group
symmetries. Realization of altermagnetism in the two-dimensional (2D) limit remains an outstanding challenge because dimensional reduction suppresses kZ dispersion and destabilizes the
symmetry operations essential for
spin compensation. Here, we investigate ultrathin CrSb films grown epitaxially on Bi2Te3 substrate and uncover the
evolution of altermagnetism in the 2D limit. Scanning tunneling microscopy (STM), quasiparticle interference (QPI), angle-resolved photoemission spectroscopy (ARPES), and density functional theory (DFT) calculations show that interfacial
symmetry breaking in the one-unit-
cell (1 UC) limit gives rise to localized electronic states and uncompensated
magnetic moments. These interfacial effects become weakened from 7/4 UC, accompanied by the recovery of a bulk-like coordination environment and the emergence of altermagnetic electronic characteristics. Our results show that the essential altermagnetic electronic structure of CrSb survives at a thickness of only ~1.05 nm, demonstrating the robustness of altermagnetism in the 2D limit and opening opportunities for integrating stray-field-free
spin order into low dimensional spintronic architectures.
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All authors Keren Li, Yuzhong Hu, Yue Li, Ruohang Xu, Shaozhong Ma, Heping Li, Kun Liu, Chen Liu, Lu Cao, Jincheng Zhuang, Yee Sin Ang, Jiaou Wang, Haifeng Feng, Weichang Hao, Yi Du
Mesoscale and Nanoscale Physics
Wiedemann-Franz behavior at the Weyl points in compressively strained HgTe
Abu Alex Aravindnath, Yi-Ju Ho, Fabian Schmitt et al. (+6 more)
Weyl semimetals, with their unique electronic band structure, have drawn significant interest for their potential to explore
quantum anomalies in condensed matter systems. In this study, we investigate the large positive magneto-thermal conductance associated with the gravitational anomaly – one of the predicted anomalies – for a Weyl semimetal based on a compressively strained HgTe layer. We clearly identify the Weyl regime in our device and accurately extract the thermal conductance by performing thermometry measurements at
liquid helium temperatures using fully electronic methods. We observe the anticipated increase in thermal conductance, and it perfectly matches the electrical conductance according to the Wiedemann-Franz law. This finding indicates that, despite the unique electronic spectrum of Weyl semimetals, the mechanism governing heat transport in this system is the same as that for electrical transport, with no additional violations of conservation laws.
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All authors Abu Alex Aravindnath, Yi-Ju Ho, Fabian Schmitt, Dongyun Chen, Johannes Kleinlein, Wouter Beugeling, Hartmut Buhmann, Stanislau U. Piatrusha, Laurens W. Molenkamp
Materials Science
DiffCrysGen: A Generative Diffusion Model for Accelerated Design of Inorganic Crystalline Materials
Sourav Mal, Nehad Ahmed, Junaid Jami et al. (+2 more)
Efficient exploration of the vast chemical space is a fundamental challenge in materials design and discovery, particularly for designing functional inorganic crystalline materials with targeted properties.
Diffusion-based generative models have emerged as a powerful route, but most existing approaches require domain-specific constraints and separate
diffusion processes for atom types, atomic positions, and
lattice parameters, adding complexity and limiting efficiency. Here, we present DiffCrysGen, a fully data-driven, score-based
diffusion model that generates complete
crystal structures in a single, end-to-end
diffusion process. This unified framework simplifies the model architecture and accelerates sampling by two to three orders of magnitude compared to existing methods without compromising chemical and structural diversity of the generated materials. In order to demonstrate the efficacy of DiffCrysGen in generating valid and useful materials, using density functional theory (DFT), we validate a number of newly generated rare earth-free
magnetic materials that are energetically and dynamically stable, and are potentially synthesizable. These include ferromagnets with high saturation magnetization and large magnetocrystalline anisotropy, as also metallic antiferromagnets. These results establish DiffCrysGen as a general platform for accelerated design of functional materials.
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All authors Sourav Mal, Nehad Ahmed, Junaid Jami, Subhankar Mishra, Prasenjit Sen
Quantum Gases
Geometric filtering effect in expanding Bose-Einstein condensate shells
Andrea Tononi, Maciej Lewenstein and Luis Santos
A shell-shaped Bose-Einstein condensate released from its confinement expands radially both outwards and inwards, displaying a self-interference pattern characterized by a density peak surrounded by a
halo. Here we analyze how an external imprinting or the thermal fluctuations of the condensate phase influence this expansion. In both cases, we find that the curved geometry filters the imploding finite angular-momentum modes via a radial centrifugal potential, so that only the condensate state can reach the origin and form the central peak. As a consequence, we observe a pronounced dependence of the central density on the imprinting strength and on temperature. This
geometric filtering effect characterizes the free expansion of curved atomic gases in contrast with flat counterparts, it is easily observable in the available experimental platforms, and enables two-dimensional shells thermometry via simple absorption-imaging techniques.
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Disordered Systems and Neural Networks
Train Stochastic Non Linear Coupled ODEs to Classify and Generate
Stefano Gagliani, Feliciano Giuseppe Pacifico, Lorenzo Chicchi et al. (+4 more)
A general class of dynamical systems which can be trained to operate in classification and generation modes are introduced. A procedure is proposed to plant asymptotic stationary attractors of the deterministic model. Optimizing the dynamical system amounts to shaping the architecture of inter-nodes connection to steer the
evolution towards the assigned
equilibrium, as a function of the class to which the item - supplied as an initial condition - belongs to. Under the
stochastic perspective, point attractors are turned into probability distributions, made analytically accessible via the linear noise approximation. The addition of noise proves beneficial to oppose
adversarial attacks, a property that gets engraved into the trained adjacency
matrix and therefore also inherited by the deterministic counterpart of the optimized
stochastic model. By providing samples from the target distribution as an input to a feedforward neural network (or even to a dynamical model of the same typology of the adopted for classification purposes), yields a fully generative scheme. Conditional generation is also possible by merging classification and generation modalities. Automatic disentanglement of isolated key features is finally proven.
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All authors Stefano Gagliani, Feliciano Giuseppe Pacifico, Lorenzo Chicchi, Duccio Fanelli, Diego Febbe, Lorenzo Buffoni, Raffaele Marino
Superconductivity
Superconductivity in monolayer-trilayer phase of La$_3$Ni$_2$O$_7$ under high pressure
Chaoxin Huang, Jingyuan Li, Xing Huang et al. (+7 more)
The discovery of 80 K superconductivity in pressurized
bilayer Ruddlesden-Popper (RP) nickelate La$_3$Ni$_2$O$_7$ has established a new high-temperature
superconductor family. The quest to understand the governing principles of RP nickelate superconductivity has become a central focus in condensed matter physics. Here, we report a critical advance by synthesizing and investigating a distinct structural polymorph of the same compound: the monolayer-trilayer (1313) hybrid phase of La$_3$Ni$_2$O$_7$. Under high pressure, synchrotron X-ray diffraction and Raman spectroscopy reveal a structural transition from the orthorhombic $Cmmm$ to the tetragonal $P4/mmm$ space group at 13~GPa. Above 19 GPa, the phase exhibits a clear superconducting transition, confirmed by a zero-resistance state, albeit at a significantly reduced temperature of 3.6 K. The stark contrast with the 80 K transition in the
bilayer phase provides a uniquely clean experimental comparison. Our results demonstrate that the superconducting transition temperature is directly governed by the nature of the interlayer coupling, and the
bilayer NiO$_6$ block as the essential structural motif for achieving high-$T_\text{c}$ superconductivity in the RP nickelates.
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All authors Chaoxin Huang, Jingyuan Li, Xing Huang, Hengyuan Zhang, Deyuan Hu, Mengwu Huo, Xiang Chen, Zhen Chen, Hualei Sun, Meng Wang
Soft Condensed Matter
Generalized Fokker-Planck equation for the active Brownian motion
Sanju S Pillai, M Muhsin and M Sahoo
We investigate the dynamics of an inertial active Ornstein-Uhlenbeck particle suspended in a non-Markovian environment. The particle is additionally subjected to external forces, such as harmonic confinement and a
magnetic field. Motivated by the importance of understanding the non-Markovian behavior of complex environments, we examine the impact of a viscoelastic medium by employing the Jeffrey fluid framework for modeling the particle motion, which effectively captures both viscous and elastic contributions of the environment. Within this model, we explicitly derive the corresponding Fokker-Planck equation for each case. Building on this, we extend the analysis to general non-Markovian framework and derive the corresponding generalized Fokker-Planck equation for a free active particle. Furthermore, we obtain the probability distribution function valid for arbitrary
memory kernel under various conditions, including both free and confined motion with and without a
magnetic field. To the best of our knowledge, this represents the first attempt to establish such a comprehensive formalism for the probabilistic description of an active particle subjected to non-Markovian
memory effects. This formulation provides a solid basis for analyzing the dynamics of an active particle in a non-Markovian environment, such as mucus and
polymer solutions, and further allows the study of relaxation in confined geometries and responses to external fields.
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Materials Science
Room temperature control of axial and basal antiferromagnetic anisotropies using strain
Jack Harrison, Junxiong Hu, Charles Godfrey et al. (+6 more)
Antiferromagnetic materials are promising platforms for the development of ultra-fast spintronics and magnonics due to their robust magnetism, high-frequency relativistic dynamics, low-loss transport, and the ability to support topological textures. However, achieving deterministic control over
antiferromagnetic order in thin films is a major challenge, due to the formation of multi-domain states stabilised by competing
magnetic and destressing interactions. Thus, the successful implementation of
antiferromagnetic materials necessitates careful engineering of their anisotropy. Here, we demonstrate strain-based robust control over multiple
antiferromagnetic anisotropies and nanoscale domains in the promising spintronic candidate a-Fe2O3, at room temperature. By applying isotropic and anisotropic in-plane strains across a broad temperature-strain phase space, we systematically tune the interplay between magneto-crystalline and magneto-elastic interactions. We discover that strain-driven control steers the system towards an aligned
antiferromagnetic state, whilst preserving topological
spin textures, such as merons, antimerons and bimerons. We directly map the nanoscale
antiferromagnetic order using linear dichroic scanning transmission X-ray microscopy integrated with in situ strain and temperature control. A Landau model and micromagnetic simulations reveal how strain reshapes the
magnetic energy landscape. These findings suggest that strain could serve as a versatile control mechanism to reconfigure
equilibrium or dynamic
antiferromagnetic states on demand in a-Fe2O3, paving the way for next-generation spintronic and magnonic devices.
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All authors Jack Harrison, Junxiong Hu, Charles Godfrey, Jheng-Cyuan Lin, Tim A Butcher, Jörg Raabe, Simone Finizio, Hariom Jani, Paolo G Radaelli
Materials Science
Spectroscopic Determination of Site-Selective Ligand Binding on Single Anisotropic Nanocrystals
Dong Le, Wade Shipley, Alexandria Do et al. (+17 more)
Organic surface ligands are integral components of nanocrystals and nanoparticles that have a strong influence on their physicochemical properties, their interaction with the environment, and their ability to self-assemble and order into higher-order structures. These hybrid nanomaterials are tunable with applications in catalysis, directed self-assembly, next-generation optoelectronics, and chemical and
quantum sensing. Critically, future advances depend on our ability to rationally engineer their surface chemistry. However, fundamental knowledge of ligand-nanoparticle behavior is limited by uncertainty in where and how these ligands bind to surfaces. For nanoparticles, in particular, few characterization techniques offer both the high spatial resolution and the precise chemical mapping needed to identify specific ligand binding sites. In this study, we utilized synchrotron infrared nanospectroscopy (SINS), atomic force microscopy (AFM), and scanning tunneling microscopy (STM) together with first-principles computer simulations to validate the site-selective adsorption of organic ligands on a shaped nanocrystal surface. Specifically, we demonstrate that the sterically encumbered isocyanide ligands (CNAr^{Mes2}) preferentially bind to the high
curvature features of Ag nanocubes (NCs), where low-coordinate Ag atoms are present. In contrast, isocyanide ligands that do not exhibit these steric properties show no surface selectivity. SINS serves as an effective tool to validate these surface binding interactions at the near-single molecule level. These results indicate that steric effects can be successfully harnessed to design bespoke organic ligands for fine-tuning nanocrystal surface chemistry and the properties of the nanocrystal ligand shell.
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All authors Dong Le, Wade Shipley, Alexandria Do, Liya Bi, Yufei Wang, Krista P. Balto, Rourav Basak, Hans A. Bechtel, Stephanie N. Gilbert Corder, Ilya Mazalov, Tesa Manto, Reno Sammons, Yutong She, Fiona Liang, Ganesh Raghavendran, Joshua S. Figueroa, Shaowei Li, Tod A. Pascal, Andrea R. Tao, Alex Frano
Mesoscale and Nanoscale Physics
Trembling motion of electrons driven by Larmor spin precession
I. Stepanov, M. Ersfeld, A. V. Poshakinskiy et al. (+4 more)
We show that the initialization of an ensemble of electrons in the same
spin state in strained n-InGaAs subject to a perpendicular
magnetic field triggers an AC electric current at GHz frequencies. The AC current emerges in the absence of any driving force and survives until the coherent precession of the electron
spins is lost. The current amplitude increases linearly with both the
spin-orbit coupling strength and the external
magnetic field. The generation mechanism of the observed oscillatory charge motion can be fruitfully described in terms of the periodic trembling motion of
spin-polarized electrons, which is a solid-state analog to the Zitterbewegung of free Dirac electrons. Our results demonstrate that the hidden consequence of relativistic
quantum mechanics is realized and can be studied in a rather simple solid-state system at moderate temperatures. Furthermore, the large amplitude of the AC current at high
magnetic fields enables ultra-fast
spin sensitive electric read-out in solids.
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All authors I. Stepanov, M. Ersfeld, A. V. Poshakinskiy, M. Lepsa, E. L. Ivchenko, S. A. Tarasenko, B. Beschoten