Soft Condensed Matter
Geometry-Controlled Dynamic Tensiometry Resolves Intrinsic Surfactant Adsorption Kinetics
Camille Brigodiot, Boxin Deng, Christine Dalmazzone et al. (+2 more)
At short times, interfacial tension depends on experimental geometry because surfactant transport to the interface depends on the mass-transfer conditions.A predictive description therefore requires more than a dynamic tension curve or a fitted adsorption constant: interfacial thermodynamics,
diffusion, and adsorption kinetics must be identified separately. Here, we combine
equilibrium and
diffusion measurements with a microfluidic EDGE tensiometer that provides a nearly stationary interface and controlled micrometer-scale transport.
Equilibrium properties and
diffusion are determined independently, leaving adsorption kinetics as the key unknown. Dynamic tension is then calculated using a nonequilibrium thermodynamic description, without assuming instantaneous
equilibrium between the adsorbed layer and the subsurface solution. For the nonionic surfactant C$_{10}$E$_{8}$,
equilibrium thermodynamics and transport are independently constrained, and a single intrinsic adsorption rate constant describes several concentrations. We extend the framework to SDS by including electrostatic interactions and subsurface-concentration dynamics, capturing transient depletion and replenishment. Once thermodynamic, transport, and kinetic parameters are identified, the model predicts dynamic interfacial tension beyond the geometry and conditions used to determine them. The microfluidic EDGE tensiometer thus provides both a reliable short-time tensiometry method and a quantitative framework for identifying the physical mechanisms governing surfactant mass transfer at interfaces.
Read the full abstract ▾
All authors Camille Brigodiot, Boxin Deng, Christine Dalmazzone, Karin Schroën, Annie Colin
Materials Science
Charge transfer and competing symmetry breaking drive orbital reconstruction and emergent ferromagnetism in insulating oxide superlattices
Nandana Bhattacharya, Ranjan Kumar Patel, Siddharth Kumar et al. (+13 more)
Electron correlation, hopping, and ligand-to-metal charge transfer collectively lead to diverse electronic and
magnetic phenomena in 3$d$ transition-metal oxides, where directional d orbitals make hopping highly sensitive to
symmetry-dependent orbital overlap.
Heterostructure engineering with atomically flat interfaces adds
symmetry-breaking charge transfer as a further route to emergent behavior, yet whether interfacial mismatch between constituent oxides of a superlattice shapes ground states independent of epitaxial strain remains unresolved. Here we examine superlattices combining NdNiO$_3$ with Mott-insulating NdMnO$_3$. Varying layer thickness and combining transport with X-ray spectroscopy, we show that electron transfer from NdMnO$_3$ to NdNiO$_3$ drives a room-temperature insulating state with a distinct electronic structure, accompanied by a reversal in orbital
symmetry beyond simple strain considerations, underscoring the interface's central role. These reconstructions stabilize an emergent ferromagnetic insulating state arising from interfacial Ni$^{2+}$-O-Mn$^{4+}$ superexchange. Our results establish a pathway to interface-engineered ferromagnetic insulating phases via competing interactions, with potential for
spin-insulatronic applications.
Read the full abstract ▾
All authors Nandana Bhattacharya, Ranjan Kumar Patel, Siddharth Kumar, Sourav Chowdhury, Manav Beniwal, Suresh Chandra Joshi, Prithwijit Mandal, Jayjit Kumar Dey, Weibin Li, Manuel Valvidares, Zhan Zhang, Hua Zhou, Andrei Gloskovskii, Christoph Schlueter, Christoph Klewe, Srimanta Middey
Materials Science
Band-like Carriers in a Soft, Anharmonic Lattice: Lead-Halide Perovskites
Young Mi Lee, Inhee Maeng, Jinwoo Park et al. (+2 more)
Lead-halide perovskites APbX3 present a striking dichotomy: they exhibit band-like electronic transport despite their exceptionally soft and anharmonic
lattices. Optically and electrically, they resemble conventional direct-gap
semiconductors, exhibiting light carrier masses and steep absorption onsets, whereas their
lattices display
liquid-like dynamics, including overdamped octahedral motions, quasielastic Raman central peaks, and exceptionally low thermal conductivities. Solution-processed films nevertheless sustain micrometre-scale carrier
diffusion at defect densities that would severely suppress transport in conventional
semiconductors. Here, we argue that these apparently disparate properties emerge from a common microscopic framework: a soft, strongly anharmonic, and polar [PbX3]- framework, strongly influenced by the Pb 6s2 lone pair, which simultaneously shapes the antibonding orbital character of the band edges, the magnitude and multiple timescales of the dielectric response, and the slow relaxational dynamics that dress every charge carrier. We therefore invert the conventional order and develop the
lattice before the electronic structure, because the nominally cubic phase is better viewed as a thermally fluctuating ensemble of locally
symmetry-broken configurations rather than a single geometry. Within this framework, we discuss
excitons, Frohlich large polarons in the intermediate-coupling regime, carrier transport, defect tolerance, dimensional reduction in two-dimensional and nanocrystalline derivatives, and
symmetry-breaking phenomena. We critically assess three contested issues - defect tolerance, ferroelectricity, and the interpretation of the T-3/2 mobility law - and identify seven open questions together with the key measurements needed to resolve them
Read the full abstract ▾
All authors Young Mi Lee, Inhee Maeng, Jinwoo Park, Seung-Jae Oh, Min-Cherl Jung
Materials Science
uMOF: A Universal Database, Benchmark, and Machine Learning Interatomic Potentials for Metal-Organic Frameworks
Théo Jaffrelot Inizan, Prathami Divakar Kamath, Alin Marin Elena et al. (+1 more)
Foundation machine learning interatomic potentials (MLIPs) deliver near-ab-initio accuracy at a fraction of the computational cost, yet their promise for Metal-organic Frameworks (MOFs) remains largely unrealized as large unit
cells make first-principles training data expensive to generate, fine-tuned models are scarce, and experimentally grounded
benchmarks are scarcer still. We introduce uMOF, a three-part contribution addressing this gap. First, we release the largest and most accurate density functional theory
dataset for MOFs to date, computed at the r$^2$SCAN-D4 level of theory across 85524 configurations spanning 19950 unique frameworks and 79 elements, covering empty and gas-loaded structures, geometry optimizations, equations of state, and finite-temperature molecular dynamics. Second, we release a literature-mined
benchmark of 3986 verified property values (3146 experimental) extracted from 626 papers by a seven-stage, checkpointed multi-pass large
language model pipeline, linked to more than 650 crystallographic information files. Third, we release two universal MLIPs for MOFs, uMOF-MH and uMOF-POLAR, fine-tuned from two architecturally distinct MACE foundation models on the uMOF
dataset. On near-
equilibrium, “Tier-1” properties (bulk modulus,
phonon-derived heat capacity) the uMOF models perform comparably to existing foundation and fine-tuned baselines. On harder, dynamics-sensitive properties like gas adsorption enthalpies via Widom insertion and adsorption isotherms, the uMOF models outperform every baseline we test, including MOF-specialized gas-capture models trained on
datasets up to three orders of magnitude larger, cutting error by more than 80% to within experimental uncertainty. We trace this advantage to the physical diversity of the training data and to level of theory where a small (1.7%) fraction of MD simulations is decisive for MLIP stability.
Read the full abstract ▾
All authors Théo Jaffrelot Inizan, Prathami Divakar Kamath, Alin Marin Elena, Kristin A. Persson
Disordered Systems and Neural Networks
Landau theory of quenched criticality in linear in-context learning
Daesik Kim, Sumin Choi, Hyojae Jeon et al. (+1 more)
In-context learning (ICL) allows a pretrained model to infer a new task from examples supplied in its
prompt without updating its parameters. In linear models of ICL, the prediction error develops a double-descent singularity when the number of pretraining samples becomes comparable to the number of learnable parameters. We formulate this interpolation singularity as a critical phenomenon of a quenched disordered system. By comparing annealed and quenched descriptions of the same linear ICL model, we identify the connected sample-to-sample fluctuations of the learned parameters as the microscopic origin of the singular error. A Landau potential is constructed by integrating the cavity self-consistency equation for the renormalized ridge parameter $\xi$. The role of (magnetization) order parameter is played by $\xi$, while the bare ridge parameter $\lambda$ becomes its conjugate
magnetic field. The normalized sample complexity $\tau$ acts as a temperature and the double-descent singularity occurs at the critical temperature $\tau_c =1$. The Landau susceptibility is precisely the quantity that diverges in the fluctuation contribution to the prediction error. The order parameter is closely related to the fraction of zero
eigenvalues of the empirical relaxation
matrix in the ridgeless limit, which define flat directions in the learning dynamics. The Landau theory is generically cubic in the order parameter with critical exponents $(\beta_{\rm cr},\delta_{\rm cr},\gamma_{\rm cr})=(1,2,1)$. In the large-context regime, there appears a pseudogap-like regime characterized by suppressed order parameter. Predictions of the Landau theory are independently confirmed from numerical solutions of the original learning problem with good quantitative agreement. Our results pave the way for solid statistical-physics understanding of the interpolation criticality in linear in-context learning.
Read the full abstract ▾
All authors Daesik Kim, Sumin Choi, Hyojae Jeon, Jung Hoon Han
Soft Condensed Matter
Weakly non-linear creep of amorphous polymers near their glass transition, comparisons between models and experiment
Martin Roman-Faure, Zhaocheng Zhang, Catalin Picu et al. (+2 more)
The non-linear mechanics of amorphous
polymers near the glass transition reveals a stress-induced acceleration of stress relaxation of nanometric sub-units. Recent theoretical work predicts that the local acceleration within these nano-domains should scale as the exponential of the squared local stress, a behavior now supported by experiments. However, this local dynamics has some complex consequences on the macroscopic mechanical response, as dynamical heterogeneities generate complex stress and strain fields in
polymers close to the glass transition. In this study we consider the non-linear creep of an amorphous
polymer near its glass transition and evaluate the relation between local and global acceleration and the emerging load-carrying structure, by comparing experimental data with predictions of three models of increasing complexity: a two-states (2S) model, a self-consistent (SC) model and a finite-element (FEM) model. The experimentally observed trend of accelerated creep under increasing applied stress is reproduced by the SC and FEM models, while the 2S model overestimates stress localization. The macroscopic, homogenized acceleration is predicted to be close to the microscopic one, albeit with an apparent yield stress that depends on compliance. The FEM model evidences the development of a load carrying sub-structure that occupies a small fraction of the total material volume driven by the interaction of sub-domains. This work shows that complexity and heterogeneity emerge due to non-linear interactions and that their adequate representation is essential for predicting the macroscopic mechanical response of amorphous
polymers near their glass transition.
Read the full abstract ▾
All authors Martin Roman-Faure, Zhaocheng Zhang, Catalin Picu, Antoine Chateauminois, Francois Lequeux
Strongly Correlated Electrons
Spin-Selective Spectral Flattening and Wave-Packet Dynamics in a Flux-Engineered Lieb Lattice
Nana Chang, Xiaoji Zhou, Yanglin Zhou et al. (+1 more)
We investigate reversible internal-state-selective wave-packet transport induced by
spin-dependent Peierls phases in a two-dimensional nearest-neighbor Lieb
lattice. The two conserved
spin components experience effective fluxes $\alpha_{\sigma}=\alpha_{0}+s_{\sigma}\alpha_{s}$, where $s_{\uparrow,\downarrow}=\pm1$. At the working point $\alpha_{0}=\alpha_{s}=1/4$, the
spin-up and
spin-down components experience $\alpha_{\uparrow}=1/2$ and $\alpha_{\downarrow}=0$, respectively. A band-resolved calculation in the $q=2$
magnetic unit
cell shows that the
spin-up spectrum contains two zero-energy flat subbands associated with the sublattice-imbalance flat-band sector, whereas the remaining four subbands retain finite bandwidths. The half-flux sector therefore fails the all-bands-flat condition and does not realize exact Aharonov–Bohm caging for a generic localized initial state. Nevertheless, real-time simulations reveal a pronounced suppression of
spin-up propagation relative to the dispersive
spin-down component, manifested by a smaller mean-square displacement and an enhanced finite-region retention probability over the pre-reflection time window. Reversing the state-dependent flux interchanges the slow and fast
spin channels, while the dynamical contrast remains robust against moderate flux detuning. These results establish
spin-dependent synthetic flux as a reversible means of controlling internal-state-resolved matter-wave transport without
spin-flip processes or interactions, and provide complementary spectral and real-space criteria for distinguishing exact caging from finite-time dynamical slowing in atomic and photonic flat-band simulators.
Read the full abstract ▾
All authors Nana Chang, Xiaoji Zhou, Yanglin Zhou, Song Ci
Statistical Mechanics
Emergent aggregation from collective foraging
Gorka Muñoz-Gil, Andrea López-Incera, Vide Ramsten et al. (+3 more)
Collective behaviour in living systems is usually modelled as the outcome of a direct social drive:
agents are rewarded, or hard-wired, to align with or approach their neighbours. Here we show that aggregation can instead emerge from an indirect objective. We let reinforcement learning foragers, initially performing a random walk, optimize their dynamics from a purely individual reward for finding replenishable targets, while perceiving only their conspecifics and never the targets themselves. As the visual range grows, the
agents undergo a sharp crossover from an environment-tuned individual search to a scale-agnostic collective one, and this crossover coincides with the onset of spatial aggregation. Thus a collective phase arises as a by-product of optimal foraging, without any direct reward for grouping. A minimal analytical first-passage model reproduces the transition as a crossover between the two search strategies. Our results identify indirect, resource-driven reward as a generic route to emergent collective phenomena.
Read the full abstract ▾
All authors Gorka Muñoz-Gil, Andrea López-Incera, Vide Ramsten, Giovanni Volpe, Thomas Müller, Hans J. Briegel
Soft Condensed Matter
Mechanics and statistics of a solvable model of an autophoretic colloidal chain
Arvin Gopal Subramaniam and Rajesh Singh
Equilibrium statistical mechanics owes much of its analytical tractability to
symmetry: detailed balance, gradient flows, and the resulting vanishing of steady-state
entropy production follow directly from the structure of the underlying dynamics, not from any smallness of the driving. Exact solutions of this kind are rare away from
equilibrium. Here we identify a class of far-from-
equilibrium active colloidal chains – coupled via roto-translational, autophoretic (monopolar) interactions – that admit an exact quasi
equilibrium description: at fixed chain geometry, the orientational equations of motion for every monomer are derivable from a scalar potential, detailed balance holds exactly in the orientational sector, while the positional sector breaks the
equilibrium structure. The associated steady-state
entropy production rate (EPR) vanishes identically for this sector, even though the full system is manifestly driven and dissipative. We solve this reduced dynamics exactly for dimers and semi-analytically for general $N$-mers, obtain the orientational fluctuations and the full-system EPR in closed form, and show that all dissipation is carried by the translational (center-of-mass) sector. We further examine the effect of dipolar chemical emission – expected from asymmetric micelle deposition at the monomer scale – and find that the
equilibrium structure holds exactly for dimers, whereas for longer chains no such description is possible. A purely dipolar coupling instead producesa genuinely non-
equilibrium state with no static attractor, sustaining non-monotonic drift with no fixed limit, and an EPR that itself never reaches steady state. Monopolar coupling remains necessary and sufficient for the polarized state; dipolar coupling alone breaks the quasi-
equilibrium structure without replacing it with a new static one.
Read the full abstract ▾
Quantum Gases
Sound propagation in one-dimensional quantum droplets
Zizhou Yuan, Jiarui Xiao and Xiao-Long Chen
Sound propagation in
quantum droplets differs from that in conventional Bose-Einstein condensates (BECs) because of their self-bound nature and the role of
quantum fluctuations. We investigate sound propagation in one-dimensional
quantum droplets formed by a symmetric Bose-Bose mixture, focusing on finite-size and confinement effects. Using the extended Gross-Pitaevskii equation, we extract the sound velocity from the real-time propagation of localized density perturbations and compare it with the low-energy excitation spectrum. We find that, unlike in a conventional BEC, the sound velocity of a finite droplet is strongly affected by its density profile and
quantum-pressure contribution. It decreases with increasing particle number as the droplet evolves from a Gaussian-like to a flat-top profile, approaching the bulk
quantum-droplet value. In contrast, external harmonic confinement compresses the droplet and enhances the sound velocity, driving the system toward the acoustic behavior of a trapped BEC. Our results establish sound propagation as a sensitive probe of finite-size effects and the crossover between self-bound
quantum droplets and conventional Bose gases, and suggest a feasible route for experimental observation in ultracold $^{39}$K droplets.
Read the full abstract ▾
Statistical Mechanics
Correlated disorder versus correlated noise: Ordering in active systems
Sudip Mukherjee and Abhik Basu
Can quenched disorder generate ordering in driven systems? Using a recently proposed hydrodynamic model, we show that sufficiently long-ranged quenched disorder can induce long-range order in two-dimensional (2D) nonreciprocal XY systems, even when the clean system exhibits only short-range order at finite noise. Active surfaces tangentially advected by quenched velocities, governed by the same hydrodynamic equation, become statistically flat with super- or subdiffusive relaxation. In three dimensions (3D), quenched disorder combined with nonreciprocity produces a novel transition between strong-coupling and asymptotically noninteracting regimes, supporting either long- or short-range order. In both 2D and 3D, the exponents are nonuniversal, which vary continuously with the degree of transversality of the quenched disorder. The degree of transversality of the quenched disorder can be tuned to induce transitions in the model for fixed disorder and noise variances.
Read the full abstract ▾
Strongly Correlated Electrons · Cross-listed from physics.chem-ph
Projected q-Shells for Nested Gausslet Bases
Steven R. White
Electronic-structure calculations require a finite representation of both the electronic wave functions and their Coulomb interaction. Conventional compact basis sets lead to a four-index interaction. Gausslet basis sets are one of a very small number of approaches that allow a much smaller two-index interaction, similar to a real-space grid, but with far fewer points. The continuing challenge in their development is reducing further the number of functions needed while maintaining high accuracy. Here we introduce projected q-shells (PQS), an improvement to the nested Cartesian gausslets of White and Lindsey. Their standard nesting construction divides a joining shell into disjoint faces, edges, and corners, reducing its
polynomial completeness from order q to order q-2. PQS approximately restores the two lost orders. In terms of completeness, we prove that for an ideal, undistorted parent, the span of the PQS basis is equivalent to an overcomplete basis of overlapping patches. Coordinate distortions, which are always used in practice, harm this equivalence only slightly. The moment properties that allow two-index interactions also become inexact, even without distortion, but we show that the improvement in order more than makes up for this loss. For similar basis sizes, PQS gives smaller one-electron and interaction errors on small molecules, such as H2+, H2, and C2, than standard nesting. The improvement is largest for more compact bases with smaller q.
Read the full abstract ▾
Soft Condensed Matter
How a polymer filling enhances the rate and selectivity of colloid permeation across mesopores
Mikhail Y. Laktionov, Frans A. M. Leermakers, Ralf P. Richter et al. (+2 more)
Polymer-functionalised mesopores are an emerging technology for colloid separation, sensing and delivery. Their potential is strikingly illustrated in living
cells, where nuclear pore complexes (NPCs) control biocolloid transport between the
nucleus and the cytosol. Even colloids much smaller than the biopolymer-filled NPC channel are effectively blocked, but some larger colloids with distinct surface features rapidly permeate. Simplistically, one may expect any
polymer filling to obstruct and slow down colloid transport. We demonstrate how a
polymer filling that attracts colloids and extends beyond the mesopore, thus maximizing colloid capture, can instead increase permeation compared to a bare pore. We also define how
polymer-filled mesopores can effectively gate colloids according to their size and surface features. Our findings provide a basic physical explanation for the exquisite permselectivity of NPCs, and a rational design strategy for novel mesopore-based separation, sensing, catalysis and drug delivery devices with enhanced performance features.
Read the full abstract ▾
All authors Mikhail Y. Laktionov, Frans A. M. Leermakers, Ralf P. Richter, Leonid I. Klushin, Oleg V. Borisov
Disordered Systems and Neural Networks · Cross-listed from physics.optics
Compact Variational Neural Networks for Spectral Inference from a Single Nonlinear 2D Perovskite Photodetector
Karl Jonas Riisnaes, Ned Thaddeus Taylor, Hoi Tung Lam et al. (+4 more)
Spectroscopy conventionally separates optical frequencies before detection, imposing persistent constraints on footprint, complexity and scalability. Here we establish an alternative paradigm in which the nonlinear optoelectronic dynamics of a single two-dimensional perovskite photodetector physically encode the incident optical field and machine learning performs the inverse spectral reconstruction. Using a planar fluorinated phenethylammonium lead iodide (F-PEAI) photodetector, we exploit wavelength- and irradiance-dependent current-voltage signatures arising from the coupled effects of photocarrier generation, trapping, interfacial transport and field-dependent carrier dynamics. A compact variational encoder-decoder preserves the functional and history-dependent structure of these responses by independently projecting forward and reverse voltage sweeps onto a truncated Legendre-
polynomial basis before mapping them through a probabilistic latent representation to continuous spectral parameters. Trained on fewer than 400 experimental voltage sweeps, the model generalises to excitation wavelengths excluded from training, reconstructing wavelength with $R^2=0.958$ and a mean absolute error of 8.1 nm, while recovering log-normalised irradiance with $R^2=0.987$. Voltage-resolved analysis further reveals that wavelength and irradiance are encoded differently across the nonlinear device response, with distinct bias regions carrying complementary optical information. These results establish nonlinear material and interface dynamics as a computational resource for spectroscopy and point towards hardware-
algorithm co-design in which materials, interfaces and inference architectures are engineered jointly to maximise information content, enabling compact spectroscopic systems without dispersive optics or detector arrays.
Read the full abstract ▾
All authors Karl Jonas Riisnaes, Ned Thaddeus Taylor, Hoi Tung Lam, Rosanna Mastria, Francesco Saverio Difeo, Monica Felicia Craciun, Saverio Russo
Statistical Mechanics · Cross-listed from hep-lat
A different kind of continuum limit for the three-dimensional U(1) gauge theory
Andreas Athenodorou, Claudio Bonati and Ivan Soler Calero
In three-dimensional compact U(1)
lattice gauge theory color confinement can be understood analytically through the dynamics of
magnetic monopoles. However, its continuum limit is pathological, since the ratio of the glueball masses to the square root of the string tension vanishes as the continuum limit is approached. We investigate a simple extension of the Wilson action in which the total number of
lattice monopoles is coupled to an additional parameter $\mu$. By tuning $\beta$ and $\mu$ simultaneously, we identify a line of constant physics along which the ratio of the lightest glueball mass to the square root of the string tension remains constant. We further show that the same scaling is satisfied, within numerical uncertainties, by the other low-lying glueball masses considered in this work. Along this trajectory, the string tension in
lattice units decreases with increasing $\beta$, thus suggesting that the modified
lattice action may provide a regularization of three-dimensional compact U(1) gauge theory with a physically well-behaved continuum limit.
Read the full abstract ▾
Mesoscale and Nanoscale Physics
Significant modulation of acoustoelectric current associated with charge density wave transitions
Natsumi Nikaido, Takuya Kawada, Koji Fujiwara et al. (+5 more)
We studied acoustoelectric (AE) currents in materials that undergo charge density wave (CDW) transitions, induced by a surface acoustic wave (SAW) on a piezoelectric substrate. The polarity and magnitude of the AE current in NbSe$_3$ and 2H-TaSe$_2$ were modulated due to their CDW transitions. We also found that the sign of the AE current depends on the SAW propagation direction with respect to the crystalline axis of the substrate.A phenomenological model assuming strain-modified conductivity can qualitatively account for the significant modulation of the AE current associated with the CDW transition, as well as the SAW propagation orientation dependence. The present results offer a powerful probe for exploring SAW-electron interactions in van der Waals materials, thereby highlighting their potential for advancing the emerging field of straintronics.
Read the full abstract ▾
All authors Natsumi Nikaido, Takuya Kawada, Koji Fujiwara, Jihoon Park, Nan Jiang, Kouta Kondou, Shintaro Takada, Yasuhiro Niimi
Soft Condensed Matter
Shape Evolution and Dynamics of Deformable Ring
Arun Kumar, Partha Sarathi Mondal, Pritha Dolai et al. (+1 more)
We numerically investigate the dynamics of a deformable closed ring filled with active particles. The ring is modeled as a flexible boundary made up of passive beads interacting with a harmonic spring force. The interior of the ring is filled with active Brownian particles (ABPs), and their activity is controlled through the rotational
diffusion coefficient. We explore how, by systematically varying the activity of ABPs, packing fraction, and size of the ring, we can control the shape deformation and dynamics of the ring. At low packing fractions, low rotational
diffusion coefficients, and smaller ring sizes, the ring exhibits highly irregular and strongly deformed shapes due to the uneven spatial arrangement of active particles along the boundary. Increasing the packing fraction, rotational
diffusion coefficient, or ring size promotes a more even distribution of active particles within the ring, thereby suppressing shape deformations and fluctuations, driving the ring toward a more circular shape. We further analyze the mean-squared displacement (MSD) of the ring's center of mass and observe a crossover from ballistic to diffusive dynamics, which can be tuned by varying the system parameters. Our results demonstrate that, despite its internal complexity and deformability, the ring exhibits emergent behavior analogous to that of a single effective active particle. This study provides insight into the collective effects of confined active matter and the resulting macroscopic dynamics of deformable systems.
Read the full abstract ▾
All authors Arun Kumar, Partha Sarathi Mondal, Pritha Dolai, Shradha Mishra
Mesoscale and Nanoscale Physics
Multi-dimensional spectroscopy of mobile excitons in two-dimensional semiconductors
Ned Wheaton, Jeffrey A. Davis, Jesper Levinsen et al. (+1 more)
Multi-dimensional coherent spectroscopy (MDCS) goes beyond standard linear-response probes and provides a powerful tool for investigating correlations between quasiparticles such as
excitons (bound electron-hole pairs). Here we present a microscopic theory of MDCS that accounts for the delocalized nature of
excitons in two-dimensional
semiconductors. In contrast to the more phenomenological few-level approaches typically employed for modelling MDCS, our theory features mobile
excitons with continuous momentum degrees of freedom. We find that the energy continuum associated with
exciton momenta is crucial for producing interaction-induced decoherence, as well as capturing the interference between different
exciton-polaron quasiparticles in the case of charge-doped
semiconductors. Crucially, our calculated MDCS spectra agree well with recent experiments on doped monolayer MoSe$_2$ [Hao et al., Nature Communications 8, 15552 (2017)], and they suggest that the interactions between
exciton polarons depend strongly on phase-space filling effects, where
exciton polarons compete for electrons. Our results demonstrate that microscopic approaches allow one to gain new insights from the fine structure of MDCS on two-dimensional
semiconductors, and they illustrate the utility of microscopic approaches to modelling MDCS experiments more generally.
Read the full abstract ▾
All authors Ned Wheaton, Jeffrey A. Davis, Jesper Levinsen, Meera M. Parish
Quantum Gases
Coherence Resonance Phenomena in an Atom-Dimer Two Mode BECs
Avinaba Mukherjee
We investigate the non-
equilibrium dynamics of atomic-molecular Bose-Einstein condensates coupled via a Feshbach resonance, with Gaussian white noise acting on both the coupling strength and the detuning. Using the bosonic Josephson-junction and Bloch-sphere formalisms, we examine how coherence (coupling) noise and imbalance (detuning) noise modify the coherence-resonance point as functions of the initial polarization and the Feshbach detuning. Noise plays a more coherent role when its characteristic timescale matches the intrinsic timescales of the dynamics, leading to extrema in the time-averaged purity and the Husimi-Q distribution.
Read the full abstract ▾
Mesoscale and Nanoscale Physics
Quantum geometric bounds at finite temperature for one-dimensional chiral systems
Peng He, Hai-Tao Ding and Yu-Guo Liu
The geometry and
topology of
quantum states are intimately related at zero temperature through exact bounds that constrain
geometric quantities from below by topological invariants. At finite-temperature, however, the analogous relations remain unclear. Here we establish rigorous
geometric lower bounds for one-dimensional (1D) chiral-symmetric systems at finite temperature within the Uhlmann's framework for mixed states. We show that the Bures length is bounded by a continuous
geometric phase angle. We further derive a temperature-dependent bound that interpolates between the zero-temperature limit and a trivial high-temperature regime. Our results are verified analytically and numerically using the Su-Schrieffer-Heeger (SSH) model and the spinless Kitaev chain model. Finally, we discuss potential ways to detect the geometry of the density
matrix in
quantum circuits, with the
quantum imaginary time
evolution (QITE) method.
Read the full abstract ▾
Statistical Mechanics
The thermodynamic freedom of a thermodynamic computer
Stephen Whitelam
Thermodynamic computers are
stochastic physical devices designed to perform calculations at the thermal energy scale. Their operation is constrained by the equations of
stochastic thermodynamics, among which are a set of bounds, known as speed limits, that relate a thermodynamic computer's run time to its computational progress and the heat it dissipates. Using the Wasserstein speed limit we assess the thermodynamic efficiency of a simulation model of a thermodynamic computer trained to perform a standard machine-learning classification task. On this task the thermodynamic computer is as capable as a simple multilayer perceptron. We show that different inference protocols allow the computer to operate within 40% of the thermodynamic limit of efficiency without loss of accuracy, or to perform inference increasingly rapidly at fixed accuracy and thermodynamic efficiency. These results indicate that a thermodynamic computer designed for a particular task retains considerable freedom in its thermodynamic operation.
Read the full abstract ▾
Soft Condensed Matter
Steady shear rheology of a granular crystal containing a single dislocation
Fumiaki Nakai
Monodisperse granular particles can form
crystals whose yielding behavior is strongly affected by dislocations and differs markedly from that of conventional amorphous granular materials. Yet the rate dependence of their post-yield steady rheology remains unclear. We use the discrete element method to study steady shear in a granular
crystal containing a single dislocation. We find that the steady shear-to-normal stress ratio $\mu_b$ is organized by the scaled dislocation velocity $v_d/v_s$, rather than by the conventional inertial number $I$. Here, $v_d$ is related to the imposed shear rate through Orowan kinematics, and $v_s$ is a characteristic Hertzian elastic-wave speed. At low $v_d/v_s$, the stress ratio approaches a small plateau associated with the elastic
lattice barrier and interparticle friction. At intermediate values of $v_d/v_s$, contact damping strongly affects the approximately linear increase of the stress ratio above the plateau. As $v_d/v_s$ approaches unity, the stress develops a stronger nonlinear velocity dependence. At still higher velocities, the coordination deficit rises sharply, marking the breakdown of crystalline order and the end of the single-dislocation description. These results identify the scaled dislocation velocity as the relevant rate variable for the steady rheology of dislocation-mediated granular flow and clarify the distinct roles of interparticle friction and contact damping in the low- and intermediate-velocity regimes, respectively.
Read the full abstract ▾
Strongly Correlated Electrons
Orbital-Selective Coexistence of Interlayer Spin-Singlet Formation and SDW Order with Anomalous Spin Reconfiguration in Bilayer Nickelate La$_{3}$Ni$_{2}$O$_{7}$ Revealed by $^{17}$O-NMR
H. Lee, M. Yashima, M. Kakoi et al. (+7 more)
The
spin structure of the
spin density wave (SDW) order in the bilayer nickelate La$_3$Ni$_2$O$_7$ has been investigated using site-selective $^{17}$O-NMR measurements on the inner apical O(1), outer apical O(2), and planar O(3,4) sites. Below $T_{\rm SDW}$ (= 150 K), the peak of all planar O(3,4) sites significantly broadens due to the emergence of a finite internal
magnetic field, whereas O(2) sites remain with no (or a negligibly small) internal field. These results are consistent with commensurate SDW order with a single
spin-spinless (or large-tiny
spin) stripe. As for the O(1) sites that bridge the NiO$_2$ planes, the internal field is nearly canceled below $T_{\rm SDW}$, indicating an antiparallel
spin configuration between adjacent planes. However, below $T_\text{A}$ ($\sim$ 115 K), the spectrum of the O(1) site disappears even though the in-plane SDW order remains robust, implying that the antiparallel
spin configuration through the Ni–O(1)–Ni bond is not particularly stable below $T_{\rm A}$, despite the expected strong interlayer
spin coupling between the NiO$_2$ planes. Above all, we emphasize that the local
spin susceptibility is extremely small at the O(2) site that has a strong covalency with the $d_{3z^2-r^2}$ orbital, indicating a well-developed interlayer
spin-singlet formation in the Ni-$d_{3z^2-r^2}$ orbitals bridging the NiO$_2$ planes. These findings shed new light on the interlayer
spin-singlet formation and the anomalous
spin reconfiguration through the $\text{Ni--O(1)--Ni}$ bonding orbitals connecting the NiO$_2$ planes, which characterize the orbital-selective nature of the bilayer nickelate La$_3$Ni$_2$O$_7$.
Read the full abstract ▾
All authors H. Lee, M. Yashima, M. Kakoi, T. Ino, Y. Arai, K. Kitagawa, H. Sakurai, Y. Takano, K. Kuroki, H. Mukuda
Quantum Gases
Microscopic Theory of Drag in a Bose Condensate Interacting with a Moving Reservoir
Hassan Alnatah, Shuang Liang, Shouvik Mukherjee et al. (+3 more)
We derive a microscopic theory of drag for a Bose-Einstein condensate interacting with a moving reservoir. Starting from interactions between a condensate and a drifting fermionic bath, we integrate out the bath degrees of freedom within the Born–Markov approximation to obtain an effective Gross–Pitaevskii equation with a drag potential. From this potential we derive an effective drag force and obtain a closed expression for the drag coefficient, determined by the reservoir density fluctuations and the condensate density profile. As an application, we simulate the drag for an
exciton–polariton condensate interacting with a drifting electron gas.
Read the full abstract ▾
All authors Hassan Alnatah, Shuang Liang, Shouvik Mukherjee, Qi Yao, Ashton S. Bradley, David W. Snoke
Materials Science
Ionization Energies, Electron Affinities, Bandgaps, Exciton Binding Energies, and Polarization Energies of Orientation-Controlled Picene, [6]-Phenacene, and [7]-Phenacene Thin Films
Rintaro Makino, Mihiro Kubo, Keiichirou Yonezawa et al. (+2 more)
Phenacenes, in which benzene rings are fused in a zigzag manner, are chemically robust $\pi$-conjugated hydrocarbons of interest for organic electronic applications and superconductivity. However, quantitative electronic parameters of phenacene thin films remain limited compared with those of acenes. Here, we determine the ionization energies (IEs), electron affinities (EAs), band gaps,
exciton binding energies, and polarization energies of orientation-controlled thin films of picene, [6]-phenacene, and [7]-phenacene using ultraviolet photoelectron spectroscopy and low-energy inverse photoelectron spectroscopy. The energy parameters depend only weakly on molecular size. In contrast, both IE and EA exhibit large orientation-dependent shifts of approximately 1 eV: lying films show IEs of 6.41-6.43 eV and EAs of 2.16-2.42 eV, whereas standing films show IEs of 5.44-5.67 eV and EAs of 1.36-1.53 eV. Nevertheless, the band gaps of approximately 4 eV and
exciton binding energies of approximately 1 eV remain nearly independent of molecular size and orientation. Analysis of polarization energies shows that the induction term is nearly orientation independent, whereas the electrostatic term strongly depends on orientation and originates primarily from molecular quadrupole moments. These results identify molecular orientation as a key factor governing frontier energy levels in phenacene thin films.
Read the full abstract ▾
All authors Rintaro Makino, Mihiro Kubo, Keiichirou Yonezawa, Hiroyuki Yoshida, Satoshi Kera
Strongly Correlated Electrons · Cross-listed from physics.comp-ph
Vectorized Symmetric and Fermionic Tensor Network Implementations for GPU-Accelerated Variational Monte Carlo
Si-Jing Du, Johnnie Gray, Ao Chen et al. (+1 more)
Variational Monte Carlo (VMC) calculations based on tensor networks (TN) have recently achieved competitive accuracy in ground-state calculations of strongly correlated
spin and fermionic systems. However, existing tensor network VMC (TN-VMC)
algorithms have not been formulated in a manner that can fully utilize GPU acceleration. We tackle the key missing ingredient, namely, the vectorized evaluation of tensor network amplitudes and tensor network operations. This ensures high GPU utilization by batching over computations with identical structure. In particular, we show how to achieve vectorization for the practically relevant case of abelian symmetric tensor networks (which includes fermionic tensor networks) by developing a “flat” tensor network formalism for block-sparse tensor representation and contraction. Using this, we construct a GPU-adapted symmetric TN-VMC workflow with batched tensor network computation. In the two-dimensional Fermi–Hubbard model, we demonstrate a GPU speedup of up to $300 \times$ over single core CPU implementations, for fermionic TN variational wavefunctions.
Read the full abstract ▾
All authors Si-Jing Du, Johnnie Gray, Ao Chen, Garnet Kin-Lic Chan
Materials Science · Cross-listed from physics.chem-ph
Mode-Specific Dynamics of $\text{CO}_2$ Hydrogenation on Copper: The Hidden Role of Molecular Rotation
Junfan Xia, Zhikai Jiang, Yaolong Zhang et al. (+3 more)
Catalytic hydrogenation of $\text{CO}_2$ to formate on copper is a key elementary step for $\text{CO}_2$ utilization. Previous experimental and theoretical studies suggested an Eley-Rideal mechanism for this reaction, promoted by bending vibrational excitation, yet direct state resolved evidence remains lacking. Here, we present first-principles dynamical predictions for $\text{CO}_2$ hydrogenation on Cu(111) based on an accurate full-dimensional neural network potential energy surface. Our calculations near-quantitatively reproduce the measured reaction probabilities, including their nozzle-temperature and incidence-energy dependence. Our state-resolved results indicate that while vibrational excitation of the bending mode enhances reactivity, it alone cannot account for the observed reactivity increase with nozzle temperature. Instead, rotational excitation plays a dominant role, mainly attributable to the significant change in anisotropy of the molecular polar orientation as $\text{CO}_2$ accesses the transition state. This mode-specific insight reinforces the hidden role of rotation in surface reactivity, opening new avenues for state-selective control of $\text{CO}_2$ hydrogenation on heterogenous catalysts.
Read the full abstract ▾
All authors Junfan Xia, Zhikai Jiang, Yaolong Zhang, Bo Peng, Hua Guo, Bin Jiang
Mesoscale and Nanoscale Physics
Subcritical bifurcation and on-off bistability in ballistic polariton condensates
Oleg I. Utesov, Soohong Choi, Pavel Kozhevin et al. (+11 more)
Dynamics of
exciton-polariton condensates under continuous-wave incoherent Gaussian optical pumping is considered. It is shown that the conventional supercritical Stuart-Landau picture is invalid in a certain domain of the parameter space. For strong polariton repulsion from the reservoir and relatively small pump spots, the dynamics is adequately described by the quintic Stuart-Landau equation. The corresponding subcritical pitchfork bifurcation leads to condensate formation, accompanied by bistability between the trivial and nontrivial states over a finite pump-power range and a one-bit
memory. Further increase of the repulsion parameter or decrease of the spot size breaks down the perturbative approach and leads to a peculiar self-trapping regime with complex dynamics. Experimental evidence of the emergence of the proposed behavior is provided. Our findings can be used to design polaritonic setups that exploit the predicted
memory effect.
Read the full abstract ▾
All authors Oleg I. Utesov, Soohong Choi, Pavel Kozhevin, Min Park, Daegwang Choi, Hyungdo Lee, Alexey N. Osipov, Alexey V. Yulin, Se Kwon Kim, Yong-Hoon Cho, Igor S. Aranson, Hyoungsoon Choi, Anton V. Nalitov, Sergei V. Koniakhin
Materials Science
Compositionally Complex Ceramics
Jian Luo
The development of high-
entropy ceramics (HECs) over the past decade has extended the high-
entropy concept to a diverse range of oxides, borides, silicides, carbides, nitrides, fluorides, silicates, and other ceramic solid solutions, encompassing increasingly diverse
crystal structures and bonding characteristics and exhibiting a broad spectrum of promising mechanical, thermal, and functional properties. Initial studies predominantly focused on five-component equimolar compositions, often assuming the formation of random solid solutions. More recently, 10-21 component ultrahigh-
entropy ceramics have been developed as a subset of HECs, some of which exhibit intriguing abrupt phase transitions. In 2020, we proposed extending the exploration of HECs to the broader class of "compositionally complex ceramics" (CCCs), in which non-equimolar compositions and long- and short-range order reduce configurational
entropy while providing additional opportunities to tailor and enhance materials properties, thereby outperforming their higher-
entropy counterparts. Dual-phase CCCs have also been reported, with thermodynamic
equilibria governing cation partitioning between the two phases and offering further opportunities to control and enhance properties through microstructural engineering. Subsequent studies have revealed grain-boundary phase-like transitions in CCCs that can control microstructural
evolution and materials properties. Overall, CCCs offer a versatile platform for tailoring materials properties through diverse
crystal structures and bonding characteristics, compositional complexity, non-equimolar designs, long- and short-range order, defects, and microstructural and interfacial engineering.
Read the full abstract ▾