Strongly Correlated Electrons
Giant number-parity effect and scalable spin squeezing in Luttinger liquids
Filippo Caleca, Saverio Bocini, Fabio Mezzacapo et al. (+1 more)
Finite-size
quantum spin systems can be magnetized by the application of a
symmetry-breaking field, but in general their
symmetry is expected to be restored once the field is turned off adiabatically. Recently (F. Caleca et al., arXiv:2412.15493) we have shown that systems of half-integer
spins with an odd number of sites and a parity-preserving
Hamiltonian can retain a finite magnetization, hence exhibiting spontaneous
symmetry breaking (SSB) at finite size. Here we generalize this phenomenon to
spin chains whose low-energy physics (in zero field) realizes a Luttinger-
liquid phase. We observe that odd-sized chains can exhibit a phenomenon of finite-size quasi-SSB, in which a net sub-extensive magnetization, $M \sim N^{1-1/(4K)}$ is retained, where $N$ is the number of sites and $K$ the Luttinger exponent. Interestingly, the states prepared by turning off the
symmetry-breaking field quasi-adiabatically display scalable
spin squeezing – namely stronger the bigger the system – regardless of the parity of $N$. The scaling of the squeezing parameter is dictated again by the Luttinger exponent, $\xi_R^2 \sim N^{-1+1/(2K)}$. This result shows that scalable
quantum correlations with metrological significance, associated typically with high-dimensional systems, can be found as well in gapless one-dimensional ones; and they are a direct consequence of the critical nature of Luttinger
liquids.
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All authors Filippo Caleca, Saverio Bocini, Fabio Mezzacapo, Tommaso Roscilde
Materials Science · Cross-listed from cs.LG
DIVIDE: A Framework for Learning from Independent Multi-Mechanism Data Using Deep Encoders and Gaussian Processes
Vivek Chawla, Boris Slautin, Utkarsh Pratiush et al. (+2 more)
Scientific
datasets often arise from multiple independent mechanisms such as spatial, categorical or structural effects, whose combined influence obscures their individual contributions. We introduce DIVIDE, a framework that disentangles these influences by integrating mechanism-specific deep encoders with a structured Gaussian Process in a joint latent space. Disentanglement here refers to separating independently acting generative factors. The encoders isolate distinct mechanisms while the Gaussian Process captures their combined effect with calibrated uncertainty. The architecture supports structured priors, enabling interpretable and mechanism-aware prediction as well as efficient active learning. DIVIDE is demonstrated on synthetic
datasets combining categorical image patches with nonlinear spatial fields, on FerroSIM
spin lattice simulations of ferroelectric patterns, and on experimental PFM hysteresis loops from PbTiO3 films. Across
benchmarks, DIVIDE separates mechanisms, reproduces additive and scaled interactions, and remains robust under noise. The framework extends naturally to multifunctional
datasets where mechanical, electromagnetic or optical responses coexist.
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All authors Vivek Chawla, Boris Slautin, Utkarsh Pratiush, Dayakar Penumadu, Sergei Kalinin
Strongly Correlated Electrons
Kagome metals
Domenico Di Sante, Titus Neupert, Giorgio Sangiovanni et al. (+5 more)
Three important driving forces for creating qualitatively new phases in
quantum materials are the
topology of the materials' electronic band structures, frustration in the electrons' motion or
magnetic interactions, and strong correlations between their charge,
spin, and orbital degrees of freedom. In very few material systems do all of these aspects come together to contribute on an equal footing to stabilize new electronic states with unprecedented properties; however the search for such systems can be guided by models of configurational motifs or key sublattices that can host such physics. One of the most fascinating structural motifs for realizing this rich interplay of frustration, electronic
topology, and electron correlation effects is the kagome
lattice. In this review, we provide an overview of the theoretical underpinnings driving the physics of kagome
lattices, and we then discuss experimental progress in realizing novel states enabled by kagome networks in crystalline materials. Different material classes are discussed with an emphasis on the phenomenologies of their electronic states and how they map to interactions arising from their kagome
lattices.
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All authors Domenico Di Sante, Titus Neupert, Giorgio Sangiovanni, Ronny Thomale, Riccardo Comin, Ilija Zeljkovic, Joseph G. Checkelsky, Stephen D. Wilson
Mesoscale and Nanoscale Physics · Cross-listed from hep-th
Orientations of Orbi-K-Theory measuring Topological Phases and Brane Charges
Hisham Sati and Urs Schreiber
Topological Chern phases of
quantum materials, as well as brane charges on M-theory orbifolds, have famously been argued to be classified by (orbi) topological K-theory, or possibly by other stable and, notably, complex-oriented
cohomology theories, such as
elliptic cohomology or Morava K-theory. However, closer inspection reveals that the most fine-grained "fragile" microscopic classification in both cases is in (orbi) Cohomotopy, which is the
primordial "unstable" or nonabelian generalized
cohomology. Coarsening takes the latter (fragile) to the former (stable)
cohomology along an nonabelian
cohomology operations. But what then is the role of complex orientation on the stable side? We observe here (i) that over gapped nodal lines in the 2D Brillouin
torus and on probe M5-branes in 11D spacetime, the cohomotopical phases/charges lift through the complex/quaternionic
Hopf fibration, and (ii) that measuring this fragile situation in stable
cohomology means equivalently to ask for universal complex/quaternionic orientation on stable
cohomology in four/ten dimensions! Then we give an explicit realization of such unstable four/ten-dimensional complex/quaternionic orientation in U(2)/Sp(2)-equivariant K-theory, using real division-algebraic tools within a new model of twisted orbifold K-theory in cohesive homotopy theory; and we explain this as an extraordinary character map from orbi Cohomotopy-twisted Cohomotopy to relative orbi K-theory. Finally, we discuss an application to the classification of 2-band crystalline topological
insulator phases sensitive to the
topology in the gapping process of their nodal line semimetal parent phase, and to the measurement of M-string charges inside M5-brane probes.
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Mesoscale and Nanoscale Physics
Bloch diode
M. Houzet, T. Vakhtel and J. S. Meyer
In a SQUID tuned away from half-integer flux (in units of the superconducting flux
quantum), the concurrence of multiple Josephson harmonics and an asymmetry between the junctions leads to the Josephson diode effect – a nonreciprocal current-voltage characteristic manifested as an asymmetry of critical currents at opposite polarities. We predict a dual version of this effect in a gate-tunable Cooper pair transistor placed in series with a highly resistive environment. When tuned away from half-integer gate charge (in units of the Cooper pair charge) it shows an asymmetry of critical voltages at opposite polarities – a dual diode effect we refer to as the Bloch diode effect. It arises from an asymmetry in the dispersion of the transistor's Bloch bands. A highly resistive environment can be realized with a Josephson junction array, suggesting that such a diode could be implemented using conventional superconducting
quantum circuits.
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Statistical Mechanics
Dissimilarity measures for generalized Lotka-Volterra systems on networks
Nicolás A. Márquez, Maryam Chaib De Mares and Alejandro P. Riascos
In this paper, we introduce a general framework to quantify dissimilarities between generalized Lotka-Volterra dynamical processes, ranging from classical predator-prey systems to multispecies communities interacting on networks. The proposed measures capture both transient and stationary dynamics, allowing systematic comparisons across systems with varying interaction parameters, network weights, or
topologies. Our analysis shows that even subtle structural changes can lead to markedly distinct outcomes: in two-species systems, interaction strength and initial conditions strongly affect divergence, while in small directed networks, differences that are invisible at the adjacency-
matrix level produce divergent dynamics. In modular networks, the fraction and distribution of negative interactions control the transition from stable to unstable dynamics, with localized perturbations within cliques yielding different global outcomes than distributed ones. Beyond structural variations, the framework also applies when modified processes follow distinct nonlinear equations, demonstrating its versatility. Taken together, these results highlight that dynamical dissimilarity measures provide a powerful tool to analyze robustness, detect structural sensitivity, and predict instabilities in nonlinear systems. More broadly, this approach supports the comparative analysis of biological systems, where complex interaction networks and nonlinear dynamics are central to stability and resilience.
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Statistical Mechanics · Cross-listed from quant-ph
Moments of Quantum Channel Ensembles
Matthew Duschenes, Diego García-Martín, Zoë Holmes et al. (+1 more)
Moments of ensembles of
unitaries play a central role in
quantum information theory as they capture the statistical properties of dynamics of systems with some form of randomness. Indeed, concepts such as approximate $t$-designs arise when comparing how close an associated moment operator of a given
unitary ensemble is to that of another, reference ensemble. Despite the importance of moment operators, their properties have not been as explored for
quantum channels. In this work we develop a theoretical framework to compute moment operators for ensembles of
quantum channels, for all moment orders $t$, with a special focus on determining ensembles that can be used as points of reference. By deriving hierarchies between ensembles, via inequalities of their moment operator norms, we give them operational meaning, and define useful concepts such as that of channel $t$-designs. Finally, we perform theoretical and numerical studies which show that different types of noise can decrease the norm of the moment operators (e.g., depolarizing noise), as well as increase it (e.g., amplitude damping noise), and generalize noise-induced concentration phenomena to channel-design-induced phenomena. Along the way, we find a block-orthogonal basis for permutations, which greatly simplifies our analyses, and may be of independent interest in moment calculations.
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All authors Matthew Duschenes, Diego García-Martín, Zoë Holmes, M. Cerezo
Materials Science
Unraveling the Surface Stability and Chemical Reactivity of Aza-Triphenylene Monolayer under O$_2$ and H$_2$O Exposure
Soumendra Kumar Das, Prasanjit Samal, Brahmananda Chakraborty et al. (+1 more)
Environmental oxidation has a great impact in tuning the physical, chemical and electronic properties of two-dimensional (2D) monolayers which can affect their practical applications in nanoscale engineering devices under ambient conditions. aza-triphenylene is a recently synthesized 2D materials whose practcal applications have not been systematically studied yet. In this study, we report for the first time, the adsorption and dissociation of O$_2$ and H$_2$O molecules on the surface of 2D aza-triphenylene monolayer through first principles calculations in combination with climbing image nudged elastic band (CINEB) method. The results indicates that both the O$_2$ and H$_2$O molecules weakly interact over the monolayer surface with an adsorption energy -0.16 eV and -0.37 eV respectively. In contrast, both the molecules exhibit resistance for dissociation due to the formation of energy barriers. The transition path indicates that molecular oxygen experience two energy barriers (0.16 ev and 1.22 eV) before getting dissociated atomic oxygen. However, the dissociation of H$_2$O requires larger energy barrier (2.3 eV and 0.86 eV) due to breaking of covalent bonds and transfer of hydrogen. The strong chemical adsorption of atomic oxygen and H$^+$/OH$^-$ ions is due to the significant charge transfer from monolayer to the adsorbate as evidenced from the charge density difference and Bader charge analysis. Moreover, the dissociated configuration exhibit a larger band gap as compared to the pristine aza-triphenylene due to the strong hybridization between the p states of carbon and oxygen. our work predicts the robustness of azatriphylene monolayer against oxygen/water exposer thus ensuring their stability for device applications using these materials.
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All authors Soumendra Kumar Das, Prasanjit Samal, Brahmananda Chakraborty, Sridhar Sahu
Quantum Gases
The role of interaction in matter wave optics with motional states
RuGway Wu, Maximilian Prüfer and Jörg Schmiedmayer
Matter-wave optics is often viewed as a linear analogue of photonics, where noninteracting particles are coherently split, diffracted, and recombined, and interference arises from single-particle coherence. In ultracold
quantum gases, however, interactions are intrinsic and can rival or exceed kinetic and optical energy scales. This drives matter-wave optics into a nonlinear regime: diffraction and momentum distributions become interaction-dependent, interference contrast degrades or collapses, and revival dynamics appear. In the mean time, interactions can generate squeezing and
entanglement, enabling sensitivities beyond the standard
quantum limit. We showcase representative examples - covering diffraction, splitting, and interferometry - that illustrate how interactions reshape the basic elements of matter-wave optics and open new opportunities for nonlinear
quantum technologies.
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Materials Science
Distortion-Driven Carrier Decoupling in Doped LiMgPO4
Zhihua Zheng, Xiaolong Yao, Cailian Yu et al. (+3 more)
The interplay between
lattice distortions and charge carriers governs the properties of many functional
oxides. In alkali-doped LiMgPO4, a significant enhancement in dosimetric response is observed, but its microscopic origin is not understood. Using non-adiabatic molecular dynamics, we reveal a fundamental mechanism of carrier decoupling driven by a hierarchy of
lattice distortions. We show that electrons localize into stable small polarons on an ultrafast timescale, trapped by the strong local potential induced by the dopant, while holes form more delocalized polarons that migrate efficiently through a
lattice smoothed by global strain. The stark contrast between the dynamics of trapped electrons and mobile holes explains the suppressed recombination and enhanced energy storage. These results present a clear physical picture of how multiscale
lattice distortions can independently control electron and hole transport, offering new insights into the physics of polarons in complex materials.
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All authors Zhihua Zheng, Xiaolong Yao, Cailian Yu, Menghao Gao, Fangping Ouyang, Shiwu Gao
Statistical Mechanics · Cross-listed from quant-ph
Ergotropy Dynamics in a Dissipative Graphene Quantum Battery
Disha Verma, Indrajith VS and R. Sankaranarayanan
We investigate ergotropy dynamics in a
graphene-based
quantum battery modeled as a four-level
spin–valley system under different dissipative environments. The battery is charged via a Gaussian pulse and subsequently evolves under amplitude damping, dephasing, and both Markovian and non-Markovian reservoirs. We find that amplitude damping, while inducing energy loss, can stabilize non-passive steady states with finite ergotropy, whereas pure dephasing suppresses coherence and eliminates work extraction. On the other hand, non-Markovian
memory slows ergotropy loss and enables partial recovery through information backflow. These results identify coherence and reservoir
memory as essential resources for enhancing the long-time performance of
graphene quantum batteries.
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Strongly Correlated Electrons
Tunable Luttinger liquid and correlated insulating states in one-dimensional moiré superlattices
Jiajun Chen, Bosai Lyu, Liguo Wang et al. (+23 more)
Two-dimensional moiré superlattices have been extensively studied, and a variety of correlated phenomena have been observed. However, their lower-dimensional counterpart, one-dimensional (1D) moiré superlattices, remain largely unexplored. Electrons in 1D are generally described by Luttinger
liquid theory, with universal scaling relations depending only on the Luttinger parameter g. In particular, at half-filling, Umklapp scattering plays a crucial role, as it can significantly change the conductance-temperature scaling relation and lead to Mott
insulators. However, this prediction has never been observed since doping an empty band to half-filling was extremely difficult. Here, we show that the marriage of moiré superlattices and 1D electrons makes it possible to study the Luttinger
liquid in an exceptionally wide filling region simply by electrical gating. We perform transport measurements on 1D moiré superlattices of carbon nanotubes on hexagonal boron nitride (hBN) substrates, and observe correlated insulating states at 1/4 and 1/2 fillings of the superlattice mini-band, where Umklapp scattering becomes dominant. We also observe a T-linear conductance at these commensurate fillings over a range of temperatures. Strikingly, the T-linear conductance leads to a strongly suppressed Luttinger parameter, suggesting a state of extreme correlation.
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All authors Jiajun Chen, Bosai Lyu, Liguo Wang, Shuo Lou, Xianliang Zhou, Tongyao Wu, Jingxu Xie, Yi Chen, Cheng Hu, Kenji Watanabe, Takashi Taniguchi, Guibai Xie, Mengzhou Liao, Wei Yang, Guangyu Zhang, Binbin Wei, Xiaoqun Wang, Qi Liang, Guohua Wang, Jie Ma, Dong Qian, Guorui Chen, Tingxin Li, Mingpu Qin, Xiao Yan Xu, Zhiwen Shi
Mesoscale and Nanoscale Physics
Inverse determination of light-matter coupling in disordered systems from transmittance spectra
Thales F. Macedo, Julián Faúndez, Antônio S. Coelho et al. (+4 more)
We investigate
quantum inverse problems in one-dimensional (1D) electronic disordered systems strongly coupled to optical cavities. More specifically, we consider the Anderson and the Aubry-Andre-Harper models connected to electronic reservoirs and embedded in a single-mode optical cavity. The light-matter interaction enables
photon-assisted hopping processes that significantly modify the transmittance spectrum. Within the nonequilibrium Green's function formalism, we implement an inversion-based approach capable of accurately extracting the electron-
photon coupling strength directly from transmittance spectra. While cavity coupling acts as a minor perturbation within the Anderson model, yielding broad yet precise parameter estimates, its influence is markedly different in the Aubry-André-Harper model. The latter exhibits a sharp metal-
insulator transition in 1D, thus resulting in more pronounced cavity-induced spectral changes. This renders even more accurate inverse solutions, offering unparalleled precision in the characterization of low-dimensional disordered systems. Altogether, our results demonstrate that the
quantum inverse problem provides a robust diagnostic tool for
quantum materials, particularly effective for systems exhibiting metal-
insulator transitions.
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All authors Thales F. Macedo, Julián Faúndez, Antônio S. Coelho, Caio Lewenkopf, Mauro S. Ferreira, Felipe A. Pinheiro, Natanael C. Costa
Statistical Mechanics · Cross-listed from physics.soc-ph
Universalities in the Avalanche Dynamics of Novelties and Non-Novelties and some Notes on the Heaps law
Filippo Santoro, Alberto Petri and Francesca Tria
Unprecedented events intertwine with the repetition of the past in natural phenomena and human activities. Key statistical patterns, such as Heaps' and Taylor's laws and Zipf's law, have been identified as characterizing the dynamical processes that govern the emergence of novelties and the abundance of repeated elements. Observing these statistical regularities has been pivotal in motivating the search for modeling schemes that can explain them and clarify key mechanisms underlying the appearance of new elements and their subsequent recurrence. In this study, we analyze sequences of novel and non-novel elements, referred to as avalanches, in real-world systems. We show that avalanche statistics provide a complementary characterization of innovation dynamics, extending beyond the three fundamental laws mentioned above. Although arising from collective dynamics, some systems behave as a single instance of a
stochastic process. Others, such as natural
language, exhibit features that we can only explain by a superposition of different dynamics. This distinction is not apparent when considering Heaps' law alone, while it clearly emerges in the avalanche statistics. By interpreting these empirical observations, we also advance the theoretical understanding of urn-based models that successfully reproduce the observed behaviors associated with Heaps', Zipf's, and Taylor's laws. We derive analytical expressions that accurately describe the probability distributions of avalanches and the Heaps law beyond its asymptotic regime. Building on these results, we derive a scaling relation that we show also holds in real-world systems, indicating a form of universality in the dynamics of novelty.
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Soft Condensed Matter
Bacterial turbulence drives interfacial waves and shape dynamics in phase-separated droplets
Kan Chang, Yulin Li, Ming Yuan et al. (+3 more)
Liquid-
liquid phase separation is important across biology, physics, and materials science. Although usually studied at
equilibrium, active components-such as motor
proteins, enzymes, and synthetic microswimmers-are increasingly recognized as key players in reshaping phase separation dynamics. Yet how internally generated active stresses are transmitted to capillary interfaces to reshape three-dimensional droplet dynamics remains poorly understood. Here, we encapsulate dense suspensions of motile bacteria inside phase-separated aqueous droplets, creating a closed droplet whose interface is driven from within by bacterial
turbulence. By varying bacterial density, we control the active stress at the droplet interface. At low bacterial density, we observe scale-dependent interfacial fluctuations that propagate as waves. In this low Reynolds number regime, these waves arise from an effective inertial response, generated when active bacterial stresses balance passive viscous damping of the interface. At higher bacterial density, droplets deform strongly-exceeding the Plateau-Rayleigh instability threshold-and even form bacteria-scale filaments-a morphology without a passive counterpart. Enhanced droplet motility and accelerated coarsening accompany these shape changes. Our work shows how active stresses can reshape the morphology and dynamics of multiphase systems, offering new insight into the physics of internally driven phase-separated fluids.
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All authors Kan Chang, Yulin Li, Ming Yuan, Masaki Sano, Zhihong You, H.P. Zhang
Soft Condensed Matter
Bacterial turbulence at compressible fluid interfaces
Yuanfeng Yin, Bokai Zhang, H. P. Zhang et al. (+1 more)
Dense bacterial suspensions at fluid interfaces provide a natural platform to explore active
turbulence in a dimensional mismatch: active units are restricted to a two-dimensional surface, while the induced flows extend into the surrounding three-dimensional
liquid. Using hydrophobic Serratia marcescens at the air-water interface, we realize interfacial bacterial
turbulence as a distinct class of active
turbulence. The system exhibits compressible in-plane flows, with
vortex size initially increasing with the thickness of the underlying fluid and saturating near 100 $\mu$ m, independent of bacterial length. This behavior contrasts sharply with bulk active
turbulence, where correlation length typically scales with system size. Hydrodynamic theory, together with direct measurements of the three-dimensional flow field, shows that the coupling between interfacial and bulk flows sets the emergent length scale. Our results uncover the fundamental physics of interfacial bacterial
turbulence and open new strategies for
geometric control of collective active flows.
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All authors Yuanfeng Yin, Bokai Zhang, H. P. Zhang, Shuo Guo
Mesoscale and Nanoscale Physics
Electron Tunneling Enhances Thermal Conductance through Metal-Insulator-Semiconductor Junctions
Yizhe Liu and Bo Sun
The presence of interfaces in
semiconductor devices substantially hinders thermal transport, contributing disproportionately to the overall thermal resistance. However, approaches to enhance interfacial thermal transport remain scarce without changing the interface structure, as the intrinsic electron and
phonon properties of constituent materials set an upper limit. Here, we find a new thermal transport pathway, electronic heat tunneling, to enhance interfacial thermal conductance through metal-
insulator-
semiconductor junctions. By applying photoexcitation or bias voltage, we observe remarkable thermal conductance increases in operando, opening a new channel for efficient interfacial heat dissipation. The electron
quantum tunneling pathway is parallel to conventional
phonon-mediated interfacial thermal transport, and violates the Wiedemann-Franz law since this pathway deviates from the paradigm of diffusive transport. Moreover, we develop a tunneling mismatch model to describe the enhanced thermal conductance, originating from tunneling heat flux. Our Letter demonstrates a previously unexplored heat transport mechanism to enhance thermal conductance, bypassing the need for interface engineering. These findings emphasize the essential need to understand
semiconductor thermal properties under realistic operating conditions.
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Statistical Mechanics
Symmetry-based nonlinear fluctuating hydrodynamics in one dimension
Yuki Minami, Hiroyoshi Nakano and Keiji Saito
We present a
symmetry-based formulation of nonlinear fluctuating hydrodynamics (NFH) for one-dimensional many-particle systems with generic homogeneous nearest-neighbor interactions. We derive the hydrodynamic equations solely from
symmetry and conservation principles, ensuring full consistency with thermalization. Using the dynamic renormalization group, we identify a KPZ-type fixed point, characterized by the dynamical exponent $z=3/2$ for both the sound and heat modes. Extensive numerical simulations of the derived NFH equations confirm this exponent and further reveal that both modes are close to the universal KPZ scaling function, the Prahofer-Spohn function. These findings establish a unified,
symmetry-based framework for understanding universal transport and fluctuation phenomena in one-dimensional nonequili brium systems, independent of microscopic details.
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Soft Condensed Matter
A Complex Topological Phase in C-Spin Active Matter
Alessandro Scirè
This work introduces a new theoretical model for active matter ("complementary-
spins" or c-
spins), exploring the interplay of positional and orientational order in mobile
agents with rotational freedom, divided into two populations with contrasting interactions. The system's behavior depends on its size and a control parameter (circular anisotropy) that splits the
agents' natural rotational frequencies. Key findings include distinct phases based on anisotropy: Small Anisotropy: Stable, regular
equilibrium patterns emerge. Moderate Anisotropy: Formation of complex, non-
equilibrium topological point defects (
vortex states), which are bistable with uniform patterns. These robust, self-repairing defects exhibit counter-rotating c-
spin loop trains,
spin-momentum locking, and dissipationless flow, classified by a two-valued topological charge. High Anisotropy: Transition to active
turbulence and loss of order. Statistical analysis reveals a double phase transition at a critical value: a standard
symmetry-breaking transition and a novel topological phase transition activating the
vortex complexes. Increasing system size enhances organizational complexity and the development of
spin-momentum locked transport networks. This model provides a new framework for understanding robustness and morphogenesis in living systems.
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Strongly Correlated Electrons
Principal Component Analysis of Competing Correlations in Quarter-Filled Hubbard Models
Md Fahad Equbal, S R Hassan and M. A. H. Ahsan
We present an unsupervised learning analysis of correlation hierarchies in the quarter-filled simple and extended Hubbard models by applying principal component analysis (PCA) to exact-diagonalization (ED) data on 3x4 and 4x4 cylindrical clusters. While the non-interacting limit (U=0) provides a finite-size reference, increasing on-site repulsion U induces localization and reorganizes the low-energy spectrum. For the extended model, we examine moderate (U=4) and strong (U=10) coupling regimes, where conventional structure factors reveal familiar crossovers among charge,
spin and local-pairing correlations. PCA of the corresponding correlation
matrices captures these crossovers directly from the data, without assuming predefined order parameters by identifying charge-dominated,
spin-dominated and pairing-dominated regimes through variance condensation into leading components. This establishes PCA as a transparent, model-agnostic framework for uncovering the hierarchy and competition of correlation channels in finite Hubbard clusters, providing a bridge between exact diagonalization and modern machine-learning diagnostics in strongly correlated systems.
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Statistical Mechanics
Full counting statistics for boundary driven transport in presence of correlated gain and loss channels
Katha Ganguly and Bijay Kumar Agarwalla
One of the major advances of
quantum technology is the engineering of complex
quantum channels in
lattice systems that paves the way for a variety of novel non-
equilibrium phenomena. For a boundary driven
lattice with such engineered
quantum channels, the analysis of the full counting statistics of current across boundaries has received limited
attention. In this work, we consider a boundary driven free fermionic
lattice with carefully engineered correlated gain and loss channels and obtain the cumulant generating function of the steady-state particle current. We also discuss the limit for simplifying the correlated gain-loss channel to a local gain-loss channel and obtain the average current and its fluctuation in such cases. Generally, in the presence of gain-loss, the current statistics are different at the two ends of the
lattice. Hence, for both local and correlated gain-loss, we devise the conditions for which the statistics can coincide, giving rise to a $\mathcal{PT}$ symmetric balanced gain-loss scenario. A striking difference between the correlated gain-loss and their local counterpart is the emergence of nonreciprocity in the system and we observe that it has a dramatic impact in the current as well as fluctuations. Our work therefore provides interesting insights about the importance of engineered dissipators in boundary driven systems.
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Quantum Gases
Small Clusters of $^4$He Atoms in Finite-Cutoff Effective Field Theory
Betzalel Bazak
Small clusters of $^4$He atoms are
benchmark systems for universal few-body physics near the
unitary limit. We study these systems using a finite-cutoff effective field theory calibrated to low-energy observables from the realistic LM2M2 potential. The chosen two-body cutoff reproduces both the atom–atom scattering length and effective range, while a regulated three-body interaction is adjusted to the trimer and tetramer ground-state energies. We distinguish total binding energies from the one-atom separation energies $S_A^*=B_A^*-B_{A-1}$ of the shallow excited states. Ground-state energies through $A=8$ are reproduced at the few-percent level, but threshold-sensitive observables are less accurate. In particular, the calculated tetramer separation energy is $S_4^*=2.85$~mK, compared with $0.92$–$0.96$~mK in converged LM2M2 calculations, and the atom–trimer scattering length differs substantially from modern LM2M2
benchmarks. For $A\ge5$, the available excited-state
benchmarks are sparse and strongly method dependent. Comparison with another soft-core interaction suggests that the discrepancies primarily reflect short-distance physics and higher-order operators omitted from the finite-cutoff
Hamiltonian rather than numerical convergence of the
stochastic variational calculation. Finite-cutoff EFT therefore provides an efficient description of ground-state systematics, whereas shallow excited states and atom–cluster scattering require a controlled higher-order and cutoff-dependence analysis.
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Materials Science
An Active Learning Interatomic Potential For Defect-Engineered CoCrFeMnNi High-Entropy Alloy
Manish Sahoo, Akash Deshmukh, Yash Kokane et al. (+2 more)
High-
entropy alloys (HEAs) exhibit exceptional properties arising from a combination of thermodynamic, kinetic and structural factors and have found applications in numerous fields such as aerospace, energy, chemical industries, hydrogen storage, and ocean engineering. However, a large compositional space remains to be explored. Unlike conventional approaches, computational methods have shown accelerated discovery of novel
alloys in a short time. However, the lack of interatomic potentials have posed a challenge in discovering new
alloy compositions and property measurements. In the present work, we have developed a Moment Tensor Potential (MTP) trained by Machine Learning based approach using the BFGS unconstrained optimization
algorithm for the CoCrFeMnNi High-
entropy alloy. Our training set consists of various defects induced configurations such as vacancies, dislocations and stacking-faults. An active learning scheme to re-train the potential was undertaken to dynamically to add training data upon encountering extrapolative configurations during non-
equilibrium simulations. A thorough investigation of the error metrics, equation of state, uniaxial tensile deformation, nano-indentation and solid-
liquid interface stability for this
alloy was carried out, and it is seen that the MTP potential outperforms the popular Modified Embedded Atom Method (MEAM) potential on physical properties prediction. The accuracy and high computational speed are discussed using scaling performance. The potential is prepared for public use by
embedding it into the Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS) code.
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All authors Manish Sahoo, Akash Deshmukh, Yash Kokane, Jayaprakash H M, Raghavan Ranganathan
Mesoscale and Nanoscale Physics
Topological Valley Transport in Bilayer Graphene Induced by Interlayer Sliding
Jie Pan, Huanhuan Wang, Lin Zou et al. (+10 more)
Interlayer sliding, together with twist angle, is a crucial parameter that defines the atomic registry and thus determines the properties of two-dimensional (2D) material homobilayers. Here, we theoretically demonstrate that controlled interlayer sliding in
bilayer graphene induces Berry
curvature reversals, leading to topological states confined within a one-dimensional moiré channel. We experimentally realize interlayer sliding by bending the
bilayer graphene geometry across a nanoridge. Systematic electronic transport measurements reveal topological valley transport when the
Fermi energy resides within the band gap, consistent with theoretical predictions of eight topological channels. Our findings establish interlayer sliding as a powerful tool for tuning the electronic properties of
bilayer graphene and underscore its potential for broad application across 2D material systems.
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All authors Jie Pan, Huanhuan Wang, Lin Zou, Xiaoyu Wang, Lihao Zhang, Xueyan Dong, Haibo Xie, Yi Ding, Yuze Zhang, Takashi Taniguchi, Kenji Watanabe, Shuxi Wang, Zhe Wang
Materials Science
Chemical-space completeness through iterative crystal-structure generation and model adaptation
Fengyu Xie, Ruoyu Wang, Taoyuze Lv et al. (+3 more)
The emergence of deep learning has brought large-scale exploration of crystalline materials closer to practical realization. Yet, universal atomistic models face a practical trade-off between chemical generality and the accuracy, efficiency, and adaptability required for intensive exploration of specific materials systems. Within a bounded chemical system, this trade-off can be relaxed by exploiting its limited chemical complexity. Guided by this intuition, we propose a chemical-system-centric strategy that couples
crystal-structure generative models with machine-learned force fields (MLFFs) in an iterative generation-evaluation-refinement loop. Using Li–P–S as a test case, we generate approximately 70,000 candidate structures, including more than 10,000 stable-unique-novel structures. The diversity of near-
equilibrium local environments saturates within the first few iterations, accompanied by convergence of MLFF prediction errors, providing an operational measure of chemical-space completeness within bounded systems. The exploration also recovers chemically plausible P–S motifs that are absent from the pretraining databases but supported by earlier experiments. The resulting system-adapted models and structures further enable finite-$P$–$T$ phase-stability calculations, Li-ion transport screening, and electronic-structure prediction. These results suggest that chemical-system-centric exploration provides a practical route toward data-efficient and high-fidelity modeling within bounded chemical spaces.
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All authors Fengyu Xie, Ruoyu Wang, Taoyuze Lv, Yuxiang Gao, Hongyu Wu, Zhicheng Zhong
Soft Condensed Matter
Tunable Nanostructures from Inverse Surfactants
Nivedina A. Sarma, Alexandra Grigoropoulos, Mustafa Arslan et al. (+10 more)
Hierarchical materials in the natural world are often made through the self-assembly of amphiphilic molecules. Achieving similar structural complexity in synthetic materials requires understanding how various molecular parameters affect assembly behavior. In recent years, inverse surfactants – molecules with hydrophobic head groups and hydrophilic macromolecular tails – have been shown to self-assemble into supramolecular assemblies in aqueous solutions that show promise for a number of applications, including drug delivery. Here, we build an understanding of the morphological phase diagram of inverse surfactants using insights from scattering experiments, computer simulations, and statistical mechanics. The scattering and simulation results reveal that changing the head-group size is an important molecular knob in controlling morphological transitions. The molecular size ratio of the hydrophobic group to the hydrophilic emerges as a crucial dimensionless quantity in our theory and plays a determining role in setting the micelle structure and the transition from mesoscale to macroscale aggregates. Our minimal theory is able to qualitatively explain the key features of the morphological phase diagram, including the prevalence of fiber-like structures in comparison to spherical and planar micelles. Together, these findings provide a more complete picture for the molecular dependencies of assemblies of inverse surfactants, which we hope may aid in the de novo design of supramolecular structures.
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All authors Nivedina A. Sarma, Alexandra Grigoropoulos, Mustafa Arslan, Erika E. Salzman, Panagiotis Christakopoulos, Honghai Zhang, Kelsey G. DeFrates, Joakim Engström, Peter V. Bonnesen, Sai Venkatesh Pingali, Ting Xu, Phillip B. Messersmith, Ahmad K. Omar