Peer Revenue Publish or profit

Papers

Fresh from arXiv, typeset properly. Highlighted words trade on the market.

Physics Condensed Matter

cond-mat Watch Condensed Matter

Friday 27 March

Mesoscale and Nanoscale Physics

Towards twisted, topological, and quantum graphene plasmonics

A. Octávio Soares and Nuno M. R. Peres

In this article, we analyze the quantum and topological properties of graphene-based plasmonic systems. We consider the following plasmonic materials: single-layer graphene, twisted bilayer graphene, and other graphene stackings, as well as the following architectures: graphene-based gratings, grids, chains of graphene disks, and the kagomé lattice.
Read the full abstract

Soft Condensed Matter

Liquid-state structural asymmetry governs species-selective crystallization in multicomponent systems

Rikuya Ishikawa, Kyohei Takae, Daisuke Takegami et al. (+2 more)

Multicomponent crystals are often assumed to form nearly random solid solutions when thermodynamically stable. However, crystal growth proceeds from structurally heterogeneous liquids, raising the possibility that the liquid state may influence which species are incorporated into the growing crystal. Here we demonstrate that liquid-state structural asymmetry can induce species-selective crystallization in multicomponent systems. Using molecular dynamics simulations of a multivalent rocksalt-type model (AgPbBiTe$_3$), we find that cations with higher valence readily form locally crystal-compatible coordination environments in the liquid and are efficiently incorporated into the growing lattice, whereas lower-valence cations exhibit more disordered liquid coordination and attach less efficiently at the crystal-liquid interface. This asymmetry leads to species-selective incorporation and slower crystal growth. Depth-resolved photoelectron spectroscopy measurements on AgPbBiTe$_3$ further reveal enhanced Ag concentration near grain-boundary and surface regions, consistent with the selective incorporation predicted by the simulations. These results demonstrate that structural compatibility between liquid-state structure and the target crystal motif governs selective incorporation during crystallization, providing a general kinetic mechanism by which compositional heterogeneity can emerge during growth of multicomponent crystals.
Read the full abstract

All authors Rikuya Ishikawa, Kyohei Takae, Daisuke Takegami, Yoshikazu Mizuguchi, Rei Kurita

Quantum Gases

Phase Coherence of Strongly Interacting Bosons in One-Dimensional Optical Lattices

R. Vatré, G. Morettini, J. Beugnon et al. (+3 more)

Ultracold Bose gases in one-dimensional optical lattices constitute an important benchmark problem in the study of strongly interacting many-body quantum phases. Here we present a combined experimental and theoretical study of their phase-coherence properties over a wide range of lattice depths. Experimentally, we extract the single-particle correlation function directly from the measured momentum distribution. Theoretically, we perform tensor-network simulations of the Bose-Hubbard model that incorporate all relevant experimental parameters. For deep lattices well within the Mott insulator regime, the experimental results are in good agreement with the expected zero-temperature behavior, with only small temperature-dependent corrections. As the lattice depth is reduced, finite-temperature effects become increasingly important. We find that the experimental data are quantitatively described by an effective temperature extracted from the tensor-network simulations, and that this effective temperature decreases markedly with increasing lattice depth. Rather than indicating actual cooling, we interpret this behavior as evidence of inhibition of thermalization caused by the formation of Mott domains that suppress heat transport. Counterintuitively, the inhibition of thermalization favors the preparation of an effectively low-entropy quantum gas in the trap center for large lattice depths.
Read the full abstract

All authors R. Vatré, G. Morettini, J. Beugnon, R. Lopes, L. Mazza, F. Gerbier

Statistical Mechanics

Crossover Scaling of Binder Cumulant and its application in Non-reciprocal Sandpiles

Wei Zhong and Youjin Deng

In this letter, we unveil a robust, pre-asymptotic scaling regime for the Binder cumulant $U_L$, a central finite-size scaling tool, demonstrating $U_L\sim N^{-1} |t|^{-d\nu}$ (disordered phase) and $\frac{2}{3}-U_L\sim N^{-1} |t|^{-d\nu}$ (ordered phase), with $t$ being the reduced control parameter, and $N$, $d$, $\nu$ represent the total number of sites, the dimensionality, and correlation length exponent, respectively. Leveraging this result, we resolve a fundamental question on the stability of universality classes under the breaking of microscopic reciprocity. For the conserved Manna sandpile, we show that reciprocal biases preserve its universality class, merely shifting the critical point. In striking contrast, any non-reciprocal interaction acts as a relevant perturbation, decisively driving the system's critical exponents to flow from their non-mean-field values towards the mean-field related ones. This flow establishes non-reciprocity as a generic mechanism inducing mean-field criticality in conserved, non-equilibrium systems.
Read the full abstract

Soft Condensed Matter

Evolution of Linear Viscoelasticity across the Critical Gelation Transition

Yogesh M Joshi

In this work, we develop a rigorous theoretical framework for the evolution of linear viscoelastic properties across the sol-gel transition. More specifically, we derive general admissible expressions for the relaxation modulus and dynamic moduli as the critical gel state is approached from the pre-gel or the post-gel side. These expressions possess a generalized multi-mode series representation and recover the critical gel power law spectrum in the limit of vanishing distance from the gel point. We validate these expressions against the experimental data for various polymeric and colloidal systems. A central finding of the present work is the requirement of continuity of the dynamic moduli and their derivatives at the critical gel point, which imposes a profound physical constraint, necessitating the relaxation dynamics on both sides of the transition to be symmetric. This, in turn, leads to the hyper-scaling relation, which is a theoretical requirement rather than an empirical proposal. We further show that the critical relaxation exponent (n) always remains above the relaxation scaling exponent (\kappa), establishing a previously unrecognized lower bound on n. We also analytically estimate, for the first time, the parameter C that characterizes the relative evolution of the storage modulus with respect to the loss modulus as the critical state is approached. These results reveal that the symmetry, scaling, and hyperscaling properties of the sol-gel transition are all consequences of a single unifying physical requirement originating from the continuity of the linear viscoelastic properties at the critical gel point.
Read the full abstract

Mesoscale and Nanoscale Physics

Comparing the orbital angular momentum and magnetic moment of magnons in the Kagome antiferromagnet with negative spin chirality

Youngjae Jeon, Jongjun M. Lee, Suik Cheon et al. (+1 more)

The orbital dynamics of magnons have recently drawn interest due to their potential roles in thermal and orbital transport phenomena in magnetic insulators. In this study, we investigate the orbital magnetic moment (OMM) and orbital angular momentum (OAM) of magnons in a Kagome antiferromagnet with negative vector chirality, focusing on the distinction between thermodynamic and wave-packet-based definitions. We compute the Berry curvature, the OMM, and the OAM in momentum space under an external magnetic field. Our results reveal a quantitative difference between the OMM and OAM, yet their associated Nernst coefficients exhibit similar temperature and field dependence in transport. Our results provide a quantitative comparison between the thermodynamic and wave-packet formulations of magnon orbital dynamics.
Read the full abstract

All authors Youngjae Jeon, Jongjun M. Lee, Suik Cheon, Hyun-Woo Lee

Materials Science

Composition-dependent bulk properties of intercalated transition metal dichalcogenides $Co_{1/3(1\pm\delta)}NbS_{2}$

Woonghee Cho, Kiwan Nam, Yeochan An et al. (+4 more)

We report a systematic study of the composition-dependent bulk properties in $Co_{1/3(1\pm\delta)}NbS_{2}$ single crystals across a series of precisely controlled cobalt compositions with -4%<$\delta$<8%. By tuning the cobalt stoichiometry, we find that the topological Hall effect is critically sensitive to the intercalant cobalt composition and is completely suppressed when the cobalt composition exceeds $\delta$=+4%. We observe that the longitudinal conductivity is also strongly influenced by the cobalt composition, reaching its maximum value just before the disappearance of the topological Hall effect. Furthermore, heat capacity measurements reveal distinct Sommerfeld coefficients ($\gamma$) across different compositions, which exhibit a clear linear scaling with the inverse of the ordinary Hall coefficient ($R_H^{-1}$). These results demonstrate that composition tuning in $Co_{1/3(1\pm\delta)}NbS_{2}$ systematically modifies the low-energy electronic degree of freedom, moving beyond a simple dilute impurity picture. Finally, we use the microscopic spin Hamiltonian to explain the stability of experimentally observed M-point modulation vector and the corresponding triple-Q magnetic order. Our findings highlight that the topological properties of this system are highly tunable through precise control of the intercalant concentration, offering a new perspective on the competition between electronic and magnetic orders in intercalated transition-metal dichalcogenides.
Read the full abstract

All authors Woonghee Cho, Kiwan Nam, Yeochan An, You Young Kim, Myung-Hwa Jung, Kee Hoon Kim, Je-Geun Park

Materials Science

ZEBRA-Prop: A Zero-Shot Embedding-Based Rapid and Accessible Regression Model for Materials Properties

Ryoma Yamamoto, Akira Takahashi, Kei Terayama et al. (+2 more)

Large language models (LLMs) exhibit substantial potential across diverse scientific disciplines, including materials science. A property prediction framework, ZEBRA-Prop (Zero-Shot Embedding-Based Rapid and Accessible Regression Model for Materials Properties), is presented here as an extension of LLM-Prop. In contrast to LLM-Prop, which requires task-specific fine-tuning of the LLM, ZEBRA-Prop eliminates fine-tuning, thereby reducing computational cost and enabling rapid model training. The framework employs MatTPUSciBERT, an LLM specialized for materials science, to enhance predictive capability. Multiple textual embeddings are incorporated through a learnable weighting mechanism, which alleviates the context-length constraints inherent in LLM-Prop and facilitates effective integration of diverse textual representations. Evaluation is conducted using two datasets: the TextEdge dataset (approximately 140,000 entries) and an in-house dataset (approximately 2,000 entries) derived from the Materials Project database, with physical properties obtained from first-principles calculations. The predictive performance of ZEBRA-Prop is close to that of LLM-Prop, while the training time is reduced by approximately 95%. The performance improvements are attributable to three principal factors: domain-specific LLM utilization, diversified textual descriptions, and systematic text preprocessing. ZEBRA-Prop constitutes a scalable and computationally efficient framework for materials property prediction and supports accelerated materials discovery, particularly under limited computational resources.
Read the full abstract

All authors Ryoma Yamamoto, Akira Takahashi, Kei Terayama, Yu Kumagai, Fumiyasu Oba

Other Condensed Matter · Cross-listed from physics.optics

Synchronization-induced flat bands in driven-dissipative dimer-waveguide chains

A. N. Osipov, I. G. Savenko, Sergej Flach et al. (+1 more)

Flat bands in driven-dissipative systems offer a route to engineer strongly localized, long-lived excitations, yet their selective population via incoherent pumping remains an open challenge. We study a one-dimensional chain of coupled lasing dimers arranged in a cross-stitch geometry and show that the synchronization regime of the individual dimers, controllable through pump intensity or inter-resonator distance, determines the character of the flat band hosted by the chain. In the in-phase (ferromagnetic) regime, the flat band appears as a subdominant, damped mode in the linear excitation spectrum. In the antiphase (antiferromagnetic) regime, by contrast, the dimers decouple and the flat band becomes the dominant, neutrally stable mode: it corresponds to an infinite family of Goldstone modes arising from the independent phase rotations of non-interacting dimers, and its compact localized states are directly observable in the noise response spectrum. Switching between these two regimes via pump control constitutes a pump-induced phase transition of the lasing lattice. Our results establish synchronization engineering as a practical mechanism for selective flat-band population in driven-dissipative optical systems, and open new avenues for studying flat-band physics, including nonlinear effects, Fano resonances, and excitation coherence in experimentally accessible laser and polariton platforms.
Read the full abstract

All authors A. N. Osipov, I. G. Savenko, Sergej Flach, A. V. Yulin

Soft Condensed Matter

Spontaneous oscillations and geometric cutoff in confined bacterial swarms

Bing Miao and Lei-Han Tang

Self-organized dynamic patterns in dense active matter are striking manifestations of non-equilibrium physics. A prominent example is the macroscopic elliptical motion observed in quasi-2D bacterial suspensions, which has lacked a physical explanation. Here, we examine a minimal linear response framework coupling bacterial swimming dynamics with fluid flow, treating long-range hydrodynamic interactions as a macroscopic communication channel. We demonstrate that microscopic swim motion, via Jeffery coupling, manifests as a “phase-leading” response to local shear flows. System-wide sustained oscillations, on the other hand, require both a critical bacterial density and strict geometric confinement. By analytically predicting the onset cell density and maximum film thickness, our model achieves excellent quantitative agreement with experiments, establishing a unified physical framework for self-organized periodic motion of elongated body in active fluids.
Read the full abstract

Materials Science

Computational Insights into PEMFC Durability: Degradation Mechanisms, Interfacial Chemistry, and the Emerging Role of Machine Learning Potentials

Jack Jon Hinsch and Kazushi Fujimoto

Proton exchange membrane fuel cells (PEMFCs) are a promising clean energy technology, offering high efficiency and near-zero operational emissions for stationery and automotive applications. However, their widespread adoption remains limited by insufficient durability, driven by the degradation of the catalyst layer and proton exchange membrane under realistic operating conditions. While the macroscopic consequences of degradation are well established experimentally, the atomistic and molecular mechanisms that initiate and propagate failure remain incompletely understood. This review synthesizes recent advances in computational modelling, spanning density functional theory, molecular dynamics, and emerging machine learning potentials, to examine how chemical, mechanical, electrochemical, and contamination driven degradation mechanisms operate across multiple length and time scales. Key topics include radical-induced membrane degradation, platinum dissolution and carbon support corrosion, mechanical fatigue under electrical and hygrothermal cycling, and the impact of ionic and gaseous contaminants. A central finding is that these degradation pathways are not independent, but form strongly coupled feedback loops that no existing computational framework has been designed to capture this coupling simultaneously. Future directions are proposed, with emphasis on multiscale modelling frameworks and the application of machine learning interatomic potentials to the electrified interface.
Read the full abstract

Other Condensed Matter

Floquet-driven thermal transport in topological Haldane lattice systems

Imtiaz Khan, Muzamil Shah, Ambreen Uzair et al. (+2 more)

In this paper, we employ a modified Haldane lattice model to investigate the light-driven, spin- and valley-dependent anomalous Nernst effect in two-dimensional hexagonal topological systems. We demonstrate that two-dimensional buckled materials exhibit a hierarchy of electrically and optically tunable topological phases when subjected to off-resonant circularly polarized light in the presence of intrinsic spin-orbit coupling and a staggered sublattice potential. Within a Berry-curvature-driven transport framework, we systematically analyze charge-, spin-, and valley-resolved anomalous Nernst responses and identify their correspondence with distinct topological regimes. A finite charge Nernst conductivity arises under optical driving combined with spin-orbit coupling, whereas the generation of a pure valley Nernst current requires the simultaneous presence of sublattice asymmetry and off-resonant light. Substrate-induced inversion asymmetry further enables thermally driven valley currents with tunable magnitude and sign. We find that single-spin and single-valley Nernst responses occur in selected insulating and metallic phases, while the valley Nernst signal is suppressed in spin-polarized and anomalous quantum Hall phases. Extending our analysis to monolayer MoS$_2$, we show that strong spin-orbit coupling and broken inversion symmetry allow fully spin- and valley-polarized Nernst currents over a broad energy window. The temperature dependence of the Nernst response exhibits characteristic signatures of topological phase transitions, establishing the anomalous Nernst effect as a sensitive probe of field-engineered band topology in two-dimensional Dirac materials.
Read the full abstract

All authors Imtiaz Khan, Muzamil Shah, Ambreen Uzair, Reza Asgari, Gao Xianlong

Mesoscale and Nanoscale Physics · Cross-listed from physics.optics

Modulating nonlinear optical responses in 3R-MoS$_2$ Fabry-Pérot microcavities

Renkang Song, Ziye Chen, Junbo Xu et al. (+10 more)

Rhombohedrally stacked transition metal dichalcogenides such as 3R-MoS$_2$ offer an exceptional platform for nonlinear optics, naturally forming Fabry-Pérot (FP) microcavities due to their giant dielectric contrast with the surrounding media. However, rigorously tracking the evolution of multiple harmonic fields within these unpatterned monolithic crystals remains a fundamental challenge. Here, we establish a self-consistent framework, spanning from linear broadband reflectance to second- and third-harmonic generation (SHG and THG), to systematically decode these nonlinear behaviors. Moving beyond conventional models, we demonstrate that the nonlinear emission is dictated by a delicate interplay among the intrinsic material absorption, the FP effects at the fundamental frequency, as well as those at the harmonic frequencies. When harmonic photons lie below the bandgap, weak absorption allows the nonlinear spectra to exhibit a complex modulation driven by the synergistic contribution of FP effects from both fundamental and harmonic waves. In stark contrast, severe intrinsic absorption of higher-energy photons heavily damps the FP effects of the harmonic fields, reducing the nonlinear response to an absorption-limited regime modulated almost exclusively by the FP effects at the fundamental frequency. By successfully decoupling these geometric and material contributions across different harmonic orders, our findings provide a precise design paradigm for engineering next-generation van der Waals photonic architectures.
Read the full abstract

All authors Renkang Song, Ziye Chen, Junbo Xu, Zerui Wang, Zitao Wu, Shenao Zhao, Wenhao Su, Ziheng Pan, Junho Choi, Vasily Kravtsov, Di Huang, Zhanshan Wang, Tao Jiang

Mesoscale and Nanoscale Physics

Assessing the classicality of photon echo from excitons in lead halide perovskite nanocrystals

George Alkhalil, Hendrik Rose, Artur V. Trifonov et al. (+9 more)

Photon echo (PE) spectroscopy is a powerful technique for probing decoherence mechanisms and charge carrier dynamics in semiconductor systems. Beyond traditional coherence measurements, characterizing the photon statistics of the echo signal is important for assessing its potential in quantum information applications and understanding the underlying quantum mechanical processes. Here, we study the photon statistics of PE signals generated by excitons in ensembles of lead halide perovskite CsPbI$_3$ nanocrystals at cryogenic temperature of 2 K using continuous-variable quantum state optical tomography based on homodyne detection. Pronounced Rabi oscillations of the PE amplitude allow us to evaluate the statistics for various pulse areas in the excitation sequence. The damping of the oscillations with increasing pulse area is attributed to spatial excitation inhomogeneity and excitation-induced dephasing. Despite the large ensemble of optically addressed excitons, the efficiency of generated PE signals is low which is attributed to the complex energy level structure of excitons and non-radiative recombination channels in CsPbI$_3$ nanocrystals. We analyze the statistical characteristics of PE via the second-order correlation function $g^{(2)}(0)$ and the characteristic function for different combinations of the areas of the excitation pulses. Our results show that $g^{(2)}(0) = 1$, and the characteristic function of the PE signal corresponds to classical behavior. The formation of photon echoes as well as $g^{(2)}(0) = 1$ at the echo time is reproduced by a quantized free-space multimode model. Despite the relatively low efficiency, the photon echo exhibits a high degree of coherence and minimal classical noise, consistent with Poissonian statistics.
Read the full abstract

All authors George Alkhalil, Hendrik Rose, Artur V. Trifonov, Polina R. Sharapova, Jan Sperling, Dmitri R. Yakovlev, Elena V. Kolobkova, Maria S. Kuznetsova, Marc Aßmann, Manfred Bayer, Torsten Meier, Ilya A. Akimov

Thursday 26 March

Materials Science · Cross-listed from eess.SP

Inference-Sufficient Representations for High-Throughput Measurement: Lessons from Lossless Compression Benchmarks in 4D-STEM

Ondrej Dyck, Andrew R. Lupini, Albina Borisevich et al. (+3 more)

Four-dimensional scanning transmission electron microscopy (4D-STEM) generates multi-gigabyte datasets, creating a growing mismatch between acquisition rates and practical storage, transfer, and interactive visualization capabilities. We systematically benchmark 13 lossless compression implementations across 5 representative datasets (8~MiB to 8~GiB, 49.5–92.8% sparsity), with 10 independent runs per method. HDF5 provides built-in gzip compression, of which gzip-9 typically achieves the highest compression ratio but is slow. We therefore evaluate widely available alternatives (via hdf5plugin), including the Blosc family. As a representative comparison, blosc\_zstd achieves compression comparable to gzip-9 (mean 13.5$\times$ vs 12.3$\times$) while compressing 19–69$\times$ faster and reading 1.9–2.6$\times$ faster across datasets. Compression ratios are deterministic, and timing measurements are highly reproducible (CV $<$2%). Compression performance follows a power law with sparsity ($R^2 = 0.99$), ranging from 5$\times$ for moderately sparse data to 35$\times$ for highly sparse data. We identify six top-performing implementations optimized for different use cases and demonstrate that 4D-STEM data can be routinely compressed by $>$10$\times$. While these results provide practical guidance for lossless compression selection, the broader conclusion is that lossless compression preserves measurements but does not by itself guarantee sustainable high-throughput workflows. As detector rates rise, data handling will increasingly require inference-driven representations – i.e., deciding what must be preserved to support a scientific inference, rather than defaulting to storing fully dense raw measurements.
Read the full abstract

All authors Ondrej Dyck, Andrew R. Lupini, Albina Borisevich, Miaofang Chi, Rama K. Vasudevan, Stephen Jesse

Materials Science · Cross-listed from cs.MS

Multi-GPU fast Fourier transforms in MATLAB (for large-scale phase-field crystal simulations)

Maik Punke and Marco Salvalaglio

We present a MATLAB-based framework for two- and three-dimensional fast Fourier transforms on multiple GPUs for large-scale numerical simulations using the pseudo-spectral Fourier method. The software implements two complementary multi-GPU strategies that overcome single-GPU memory limitations and accelerate spectral solvers. This approach is motivated by and applied to phase-field crystal (PFC) models, which are governed by tenth-order partial differential equations, require fine spatial resolution, and are typically formulated in periodic domains. Our resulting numerical framework achieves significant speedups, approximately sixfold for standard PFC simulations and up to sixtyfold for multiphysics extensions, compared to a purely CPU-based implementation running on hundreds of cores.
Read the full abstract

Soft Condensed Matter

Entanglement by design: Symmetry-guided periodic helical assemblies

Myfanwy E. Evans

In this paper, a selection of elegant, highly symmetric examples of three-periodic tangled nets and filaments are presented. They are constructed via familiar crystal nets using edges as geometric scaffolds for n-fold helical windings. Rather than providing a complete classification, this gallery of examples highlights recurring geometric motifs, offering insight into how periodic tangles are organised in crystalline, molecular, and biological systems.
Read the full abstract

Mesoscale and Nanoscale Physics · Cross-listed from quant-ph

Scalable topological quantum computing based on Sine-Cosine chain models

A. Lykholat, G. F. Moreira, I. R. Martins et al. (+3 more)

This work proposes a scalable framework for topological quantum computing using Matryoshka-type Sine-Cosine chains. These chains support high-dimensional qudit encoding within single systems, reducing the physical resource overhead compared to conventional qubit arrays. We describe how these chains can be used in Y-junction braiding protocols for gate operations and in extended memory architectures capable of storing multiple qubits simultaneously. Fidelity analysis shows partial topological protection against disorder, suggesting this approach is a possible pathway toward low-overhead quantum hardware.
Read the full abstract

All authors A. Lykholat, G. F. Moreira, I. R. Martins, D. Sousa, A. M. Marques, R. G. Dias

Materials Science

Modeling key characteristics of high-efficiency gallium arsenide solar cells

A.V. Sachenko, V.P. Kostylyov, I.O. Sokolovskyi et al. (+1 more)

The paper proposes a theoretical approach to modeling the key characteristics of highly efficient gallium arsenide-based solar cells (SCs), using a one-dimensional SC model. The following recombination mechanisms are considered in the modeling: radiative recombination, interband Auger recombination, Shockley-Reed-Hall (SRH) recombination, surface recombination, recombination in the space charge region (SCR), and recombination along the perimeter of the structure. A simple empirical formula is proposed to describe the recombination along the perimeter of the SC structure. The GaAs band-gap narrowing effect is also taken into consideration. The main results are obtained under the assumption that the times of Shockley-Reed-Hall recombination and recombination in the SCR are the same. The effect of photon recycling (re-emission and re-absorption) is taken into account in a model similar to the one we used previously to simulate key characteristics of high-efficiency single-crystal silicon SCs. The model additionally uses absorption analysis at different doping levels of gallium arsenide. A good agreement was achieved between the experimental and theoretical dependencies. The results obtained in this work can be used to optimize the characteristics of highly efficient SCs based on direct-band semiconductors, particularly gallium arsenide (GaAs). Keywords: solar cell, high efficiency, modeling, gallium arsenide, recombination mechanisms, external quantum efficiency, parameter optimization.
Read the full abstract

All authors A.V. Sachenko, V.P. Kostylyov, I.O. Sokolovskyi, A.I. Shkrebtii

Quantum Gases

Extreme (Rogue) Waves: From Theory to Experiments in Ultracold Gases and Beyond

A. Chabchoub, P. Engels, P. G. Kevrekidis et al. (+4 more)

In this Chapter, we review key theoretical and experimental advances in the study of extreme nonlinear wave events, called rogue waves (RWs), in both single-component attractively interacting and two-component repulsive mixtures of ultracold quantum gases. Starting from the exact rational solutions of the integrable focusing nonlinear Schroedinger model, the hierarchy of RW solutions is exemplified. These range from the Peregrine soliton (PS) and, related to it, the destabilization into a multi-peak cascade of PSs dubbed "Christmas-tree", to the Akhmediev breather, and Kuznetsov-Ma soliton as well as higher-order RWs. Emphasis is placed on their controllable dynamical emergence and characteristics in non-integrable quantum many-body systems described by Gross-Pitaevskii models and extensions thereof through different protocols such as modulational instability, gradient catastrophe, and dam-break flows. We further discuss how immiscible particle-imbalanced repulsive mixtures can be cast into effective attractive single-component environments capable of hosting RWs. Next, state-of-the-art experimental techniques are summarized within the ultracold realm that can be utilized to realize solitary waves, modulational instability, dispersive shock waves and RWs including the very recent first experimental observation of the PS, enabled through engineered effective focusing interactions and precise dynamical triggering. Observations of these extreme events in water waves, nonlinear optics and beyond are also outlined, highlighting their broader relevance and potential of emergence in disparate physical settings. Our exposition aims at showcasing ultracold atomic gases as versatile platforms for controllably generating and probing extreme nonlinear events, among others, in the quantum realm across integrable and non-integrable settings.
Read the full abstract

All authors A. Chabchoub, P. Engels, P. G. Kevrekidis, S. I. Mistakidis, G. C. Katsimiga, M. E. Mossman, S. Mossman

Materials Science

Exciton dynamics and high-temperature excitonic superfluidity in S-doped graphyne

Enesio Marinho Jr., Alexandre C. Dias, Luiz A. Ribeiro Jr. et al. (+2 more)

S-doped graphyne (S-GY) is a recently synthesized two-dimensional graphyne-based carbon allotrope that provides a promising platform for exciton engineering and coherent many-body phases. Here, we investigate the quasiparticle electronic structure, optical response, and exciton dynamics of monolayer S-GY using the G$_0$W$_0$ approximation and the Bethe–Salpeter equation (BSE). Quasiparticle corrections increase the fundamental band gap from $0.88\,\text{eV}$ (PBE) to $1.95\,\text{eV}$, while slightly reducing the carrier effective masses. The BSE optical response reveals strongly bound excitons, with the lowest bright exciton exhibiting a binding energy of $0.72\,\text{eV}$, as well as a nearly degenerate dark exciton within the thermal energy scale. Analysis of exciton wavefunctions in reciprocal space confirms a hydrogenic Rydberg series with well-defined angular-momentum character, and radiative lifetimes in the nanosecond range at room temperature, comparable to those in transition-metal dichalcogenide monolayers. Finally, we construct the excitonic phase diagram and estimate a crossover density of $\sim6 \times10^{12}~\text{cm}^{-2}$, below which the exciton gas behaves as a dilute Bose system, and the Berezinskii–Kosterlitz–Thouless (BKT) superfluid phase becomes accessible. We estimate a maximum BKT transition temperature of $\sim 143\,\text{K}$ in the freestanding limit for the 1s exciton, indicating that monolayer S-GY may provide favorable conditions for high-temperature excitonic superfluidity in graphyne-based materials.
Read the full abstract

All authors Enesio Marinho Jr., Alexandre C. Dias, Luiz A. Ribeiro Jr., Maurizia Palummo, Cesar E. P. Villegas

Materials Science

Room-temperature antiferromagnetic resonance in NaMnAs

Jan Dzian, Stáňa Tázlarů, Ivan Mohelský et al. (+16 more)

We report on antiferromagnetic resonance experiments in bulk tetragonal NaMnAs – a room-temperature antiferromagnetic semiconductor. Our results corroborate previous ab initio studies, which propose that NaMnAs is an easy-axis antiferromagnet with the Néel vector oriented along the tetragonal axis. At $ B = 0 $, we find a single antiferromagnetic resonance line at 7 meV and associate it with a doubly degenerate ($ k = 0 $) magnon mode. Its energy softens considerably with increasing $ T $, but remains clearly visible in the data up to room temperature. From the experimental data, we estimate the single-ion anisotropy of the Mn ions in NaMnAs in the range 0.1-0.2 meV, a value that is relatively large compared to other manganese-based antiferromagnets.
Read the full abstract

All authors Jan Dzian, Stáňa Tázlarů, Ivan Mohelský, Florian Le Mardelé, Filip Chudoba, Jiří Volný, Jan Wyzula, Amit Pawbake, Simone Ritarossi, Riccardo Mazzarello, Philipp Ritzinger, Jakub Železný, Karel Výborný, Klára Uhlířová, Benoît Grémaud, Andrés Saúl, Clément Faugeras, Martin Veis, Milan Orlita

Materials Science

Cluster glass behavior and magnetocaloric effect in the hexagonal polymorph of disordered Ce$_2$PdGe$_3$

Leszek S. Litzbarski, Kamil Balcarek, Anna Bajorek et al. (+3 more)

In this work, we study the hexagonal variant of the $\text{Ce}_2\text{PdGe}_3$ system that crystallizes in the $\text{AlB}_2$-type structure (space group $P6/mmm$, $hP3$) and exhibits cluster spin glass type behavior. The physical properties were studied by magnetization, heat capacity and electric resistivity, which showed that $\text{AlB}_2$-type $\text{Ce}_2\text{PdGe}_3$ ($h\text{-Ce}_2\text{PdGe}_3$) can be classified as a cluster glass material with the freezing temperature $T_f = 3.44 \text{ K}$ in contrast to the behavior of the previously described tetragonal variant, which shows a double antiferromagnetic transition at $T_{N1} = 11 \text{ K}$ and $T_{N2} = 2.3 \text{ K}$. The X-ray photoelectron spectroscopy measurements reveal that the $\text{Ce } 4f$ states are well localized. In addition, we examine the magnetocaloric effect in this compound. The maximum values of magnetocaloric parameters appear in the vicinity of $7\text{--}9 \text{ K}$. For a magnetic field change of $50 \text{ kOe}$, the value of the change in magnetic entropy is $2.6(1) \text{ J kg}^{-1} \text{ K}^{-1}$ and the adiabatic temperature change is $\sim 8 \text{ K}$.
Read the full abstract

All authors Leszek S. Litzbarski, Kamil Balcarek, Anna Bajorek, Tomasz Klimczuk, Michał J. Winiarski, Karol Synoradzki

Materials Science

Compositional Complexity-Induced Ultralow Friction in Medium-Entropy MXenes

Jiaoli Li, Yuwei Zhang, Congjie Wei et al. (+11 more)

Two-dimensional MXenes are promising solid lubricants, but the roles of compositional complexity and surface chemistry in governing interfacial friction remain unclear. Here, we systematically investigate the adhesion and friction behaviors of medium-entropy (ME) MXenes, TiVNbMoC3 and TiVCrMoC3, and compare them with conventional titanium carbide MXenes, Ti2C and Ti3C2, using a SiO2 colloidal atomic force microscopy probe. Thermal annealing at 200 C converts OH surface terminations to O terminations, leading to pronounced reductions in adhesion energy and friction force across all MXenes studied. ME MXenes exhibit larger adhesion reductions because of their higher initial OH contents and more extensive OH-to-O conversion. In addition, their intrinsically higher out-of-plane bending stiffness suppresses energy dissipation during sliding, enabling ultralow friction. Notably, superlubricity is achieved in ME MXenes, with annealed TiVCrMoC3 exhibiting a coefficient of friction as low as 0.0022, outperforming graphene, MoSe2, and other MXenes evaluated using the same experimental approach. These findings identify compositional complexity as a powerful strategy for engineering MXenes with exceptional tribological performance and establish ME MXenes as a new class of solid lubricants.
Read the full abstract

All authors Jiaoli Li, Yuwei Zhang, Congjie Wei, Yanxiao Li, Shuo He, Risheng Wang, Brian Wyatt, Reza Namakian, Babak Anasori, Kelvin Xie, Tobin Filleter, Ali Erdemir, Wei Gao, Chenglin Wu

Strongly Correlated Electrons

Benchmarking the accuracy of superconducting pair-pair correlations within Constrained Path Quantum Monte Carlo

Jodie Roberts, Beau A. Thompson and R. Torsten Clay

Ground state properties of the Hubbard model are of fundamental importance to understand the mechanism of unconventional superconductivity in the high-T_c cuprates and other materials. One of the most powerful numerical methods for strongly interacting models is quantum Monte Carlo, which however faces a fundamental limitation, the Fermion sign problem. The sign problem can be mitigated using approximate methods such as Constrained Path Monte Carlo, where the sign of the overlap with a trial wavefunction is constrained to remain positive. Beyond the constraint, additional approximations must be made in order to measure observables for operators that do not commute with the Hamiltonian. We examine critically the most commonly used approximation, back propagation, as well as a recently proposed constraint release measurement technique. In comparisons with a variety of systems that can be solved numerically exactly by other methods, we find that back propagation tends to underestimate long-range superconducting pair-pair correlations. Except in special cases such as one dimension, back propagation introduces an uncontrolled approximation even when the exact trial wavefunction is used. The constraint release technique can provide accurate results, with the disadvantages that it much more computationally expensive and reintroduces the sign problem.
Read the full abstract

Materials Science

Decoupling dislocation multiplication and velocity effects in metals at extreme strain rates

Daniyar Syrlybayev, Lavanya Raman, Niraj Pramod Atale et al. (+4 more)

The dynamic behavior of metals is governed by collective dislocation motion and interactions that strongly depend on the applied strain rate. Metals exhibit weak strain rate sensitivity (SRS) below a certain threshold, followed by a distinct SRS upturn at higher loading rates. While this upturn is typically attributed to increased glide resistance at high dislocation velocity due to mechanisms such as phonon drag, the role of strain-rate-dependent dislocation multiplication and microstructural evolution under these extreme conditions remains elusive. Here, we decouple these two strengthening effects and show that, while dislocation velocity primarily governs the SRS upturn, the hardening due to microstructure evolution depends strongly on the initial dislocation density. Our investigation of hardness evolution across ten decades of strain rates in a quenched and tempered martensitic low-carbon steel (LCS) using laser-induced projectile impact tests (LIPIT) and nanoindentation reveals SRS upturn around 10^7 1/s. By performing in situ re-indentation of the formed craters, we probe the contribution of dislocations generated during initial deformation at different strain rates. We show that while dislocation multiplication plays a negligible role in fine-grained LCS with high dislocation density, a pronounced dislocation multiplication contributes to the hardness increase in pure iron with lower initial dislocation density. Our results show that, depending on the initial microstructure of metals, dislocation multiplication significantly governs high-strain-rate plasticity, in addition to dislocation velocity effects.
Read the full abstract

All authors Daniyar Syrlybayev, Lavanya Raman, Niraj Pramod Atale, Bhanugoban Maheswaran, Siddhartha Pathak, Curt A. Bronkhorst, Ramathasan Thevamaran

Materials Science

Universal effect of ammonia pressure on synthesis of colloidal metal nitrides in molten salts

Ruiming Lin, Vikash Khokhar, Ningxin Jiang et al. (+11 more)

Metal nitrides represent a large class of materials with extensive applications in optoelectronics, energy, and healthcare technologies. For example, GaN and related nitride semiconductors are key materials for solid-state lighting and high-power electronics, TiN and other early transition metal nitrides (TMNs) are widely used in wear-resistant alloys, tool coatings, catalysts and medical implants. Strong metal-nitrogen bonds grant nitrides structural rigidity as well as chemical and thermal stability. However, the covalency of metal-nitrogen bonds necessitates high temperatures to synthesize crystalline metal nitrides. Common synthetic routes include high-temperature solid-state nitridation, crystal growth in supercritical ammonia, molecular-beam epitaxy (MBE), reactive sputtering, and chemical vapor deposition (CVD). The solution synthesis of colloidal nitride nanocrystals (NCs) is rare and particularly challenging because commonly used solvents and surfactants decompose at temperatures far below those required for crystallization of most metal nitrides. Here we report a general approach to solution synthesis of colloidal metal nitride NCs by reacting metal halides and ammonia dissolved in molten inorganic salts at elevated pressures. Successful syntheses of colloidal TiN, VN, GaN, NbN, Mo2N, Ta3N5, W2N, as well as ternary Ti1-xVxN NCs, are demonstrated. These NCs expand the scope of solution-processable technologically important materials.
Read the full abstract

All authors Ruiming Lin, Vikash Khokhar, Ningxin Jiang, Wooje Cho, Zirui Zhou, Di Wang, Justin C. Ondry, Zehan Mi, James Cassidy, Alex M. Hinkle, John S. Anderson, Richard D. Schaller, De-en Jiang, Dmitri V. Talapin

Superconductivity

Double-peak Majorana bound states in altermagnet–superconductor heterostructures

Pankaj Sharma and Narayan Mohanta

We study Majorana bound states in a planar Josephson junction in which the middle channel is a $d$-wave altermagnetic metal deposited on a proximitized two-dimensional electron gas. In the topological regime, the near-zero-energy states reveals a characteristic double-peak spatial profile, with the Majorana wavefunction localized near the altermagnet–superconductor interfaces. Using simplified theoretical models, we show that anisotropic hopping intrinsic to altermagnetism naturally generates interface-localized low-energy states, providing the natural explanation for the double-peak structure. In a nanowire geometry with extended normal metallic regions, the same feature persists but the Majorana bound states become more sensitive to the chemical potential compared to the case in planar Josephson junction. In a T-shaped Josephson junction, multiple near-zero-energy states appear, and the Majorana bound state expected at the crossing point is found to be localized near the interfaces, demonstrating that the localization of the Majorana bound states is primarily governed by interface boundaries rather than by the junction geometry. These results show that anisotropic hopping and interface structure play a central role in altermagnet-based topological superconductors and provide a promising route toward a network of controllable Majorana bound states without external magnetic fields.
Read the full abstract

Soft Condensed Matter

Field-controlled interfacial transport and pinning in an active spin system

Mintu Karmakar, Matthieu Mangeat, Swarnajit Chatterjee et al. (+2 more)

Field control provides a practical route to programmable active matter, yet how weak fields modify non-equilibrium coexistence and interfaces remains unclear. To address this, we study a minimal flocking model of active Potts particles coupled to an external field and show that even weak fields can reconfigure phase behavior and interfacial dynamics. For a homogeneous unidirectional field, the flocking phase is reshaped: the coexistence regime between an apolar gas and a polar liquid is replaced by a phase separation between two field-aligned polar phases: a low-density, weakly polarized background and a high-density, strongly polarized band, both moving along the field. When the system forms a dense longitudinal lane oriented transverse to the field, it executes a slow treadmilling motion against the field, driven by the weakly polarized background. If the system is divided into regions with opposite field directions, particles accumulate at the interface, leading to field-induced interface pinning with flocks performing back-and-forth oscillatory motion. In the presence of quenched random field orientations, this pinning favors a disordered state in which global order diminishes with increasing system size, consistent with Imry-Ma arguments, while the quenched disorder smoothens sharp first-order signatures, in line with the Aizenman-Wehr theorem, with activity modifying the scaling. A coarse-grained hydrodynamic theory supports these observations and is consistent with microscopic simulations.
Read the full abstract

All authors Mintu Karmakar, Matthieu Mangeat, Swarnajit Chatterjee, Heiko Rieger, Raja Paul

Mesoscale and Nanoscale Physics

Scaling laws of electron and hole spin relaxation in indirect band gap (In,Al)As/AlAs quantum dots

T. S. Shamirzaev, D. R. Yakovlev, D. S. Smirnov et al. (+2 more)

We investigate the electron and heavy hole spin dynamics as a function of magnetic field in ensembles of indirect band gap (In,Al)As/AlAs quantum dots (QDs) with type-I band alignment. Employing a comprehensive model that accounts for both the exciton level quartet and the magnetic-field-driven redistribution of excitons between these states via spin relaxation processes, we extract the electron ($\tau_{se}$) and heavy hole ($\tau_{sh}$) spin relaxation times as a function of magnetic field for QDs of varying sizes. Our analysis reveals that both $\tau_{se}(B)$ and $\tau_{sh}(B)$ exhibit power-law scaling behavior, yet the scaling exponents for electrons and heavy holes show markedly different evolution with QD size. For QDs with a diameter of about 9 nm, we find $\tau_{se}(B)\propto B^{-5}$ and $\tau_{sh}(B)\propto B^{-3}$. Remarkably, increasing the QD diameter to about 16 nm results in a drastic change of the scaling laws, with both $\tau_{se}(B)$ and $\tau_{sh}(B)$ following a $\propto B^{-9}$ dependence. We discuss the underlying mechanisms responsible for this size-dependent transformation of the magnetic field scaling behavior of carrier spin relaxation.
Read the full abstract

All authors T. S. Shamirzaev, D. R. Yakovlev, D. S. Smirnov, V. N. Mantsevich, M. Bayer