Statistical Mechanics · Cross-listed from quant-ph
Over forty years of research towards the understanding of Quantum Brownian Motion – the contributions of A. O. Caldeira
Marcus V. S. Bonança, Sebastian Deffner and Gert-Ludwig Ingold
This article presents a brief account of Amir O. Caldeira's contributions to the theory of
quantum Brownian motion. Motivated by its importance, we outline the description of Brownian motion in the
quantum regime following Caldeira's first works. In this context, we particularly highlight the effect of dissipation on the tunneling rate out of a metastable state. We then journey along the alternative ways to approach
quantum Brownian motion developed by Caldeira during his career, which go beyond the so-called Caldeira-Leggett model. We conclude by summarizing some of Caldeira's contributions to contemporary fields such as the theory of
quantum decoherence and
quantum thermodynamics, that were strongly inspired by his eponymous approach to
quantum Brownian motion.
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Materials Science
Anomalous, pre-yield grain-boundary sliding in copper revealed with in-situ high-resolution strain mapping
Benjamin Poole, David Lunt, Luke Hewitt et al. (+1 more)
Grain boundary sliding is typically associated with high temperature deformation in engineering
alloys. Here, we examine grain boundary sliding at room temperature in oxygen-free high-conductivity copper under quasi-static tensile testing. By using high-resolution digital image correlation (HRDIC) conducted in-situ within a scanning electron microscope to produce time-series strain maps, we unexpectedly observe that grain boundary sliding occurs extensively prior to macroscopic yield, and before the onset of significant crystallographic slip. Extreme values in strain and in-plane rotation are found to be associated with grain boundaries immediately prior to yield and during the initial stages of plastic deformation, which are higher than those associated with crystallographic slip. By combining
laser scanning confocal microscopy height mapping with the strain maps and orientation maps from electron backscatter diffraction, grain boundary sliding character is determined, finding evidence of pure in-plane, pure out-of-plane and mixed-mode sliding.
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All authors Benjamin Poole, David Lunt, Luke Hewitt, Chris Hardie
Mesoscale and Nanoscale Physics
Influence of a graphene substrate on the stabilization of molecular systems with hydrogen bonds
Alexander V. Savin
Numerical simulation of the dynamics of planar two- and three-layer molecular structures formed by $\beta$-sheets of polyglycine peptide chains and systems of parallel Kevlar (para-aramid) molecules placed on a
graphene sheet has been performed. It is shown that in these structures the $\beta$-sheets retain their shape, due to the presence of parallel chains of hydrogen bonds, up to a temperature of $T=800$K. An even higher stability is exhibited by the system of parallel Kevlar molecules. Here, the parallel chains of hydrogen bonds between peptide groups of neighboring molecules are preserved even at higher temperatures. The performed modeling allows us to conclude that the addition of
graphene to Kevlar fibers can significantly increase their thermal stability.
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Strongly Correlated Electrons
Large magnetoresistance and weak-antilocalization in the nodal-line semimetal VP2
Chunxiang Wu, Shuijin Chen, Tingyu Zhou et al. (+8 more)
After growing successfully high quality VP$_2$ single
crystals, we studied systematically their longitudinal $\rho_{xx}(T)$ and
Hall resistivity $\rho_{yx}(T)$ at various
magnetic fields, combining the electronic band and
Fermi surface (FS) calculations. Band calculations reveal that VP$_2$ is a type-II nodal-line semimetal, evidenced by the
Hall resistivity measurements. It is found that the magnetoresistance (MR) at higher
magnetic fields exhibits a linear behavior and does not show any sign of saturation, reaching 170% at 40 K up to 9 T, which is determined by the intrinsic electronic structure and dominated by the Lorenz force, demonstrated by the resistivity anisotropy measurements and the numerical simulations. We also found that the existence of small amount
magnetic impurities (V$^{4+}$, $S=1/2$, 2.24%) results in Kondo effect emerging in $\rho_{xx}(T)$, the conductivity at lower
magnetic fields exhibits a typical weak anti-localization (WAL) behavior. These results illustrate that VP$_2$ is a platform to study the electronic transport properties of a topological material containing
magnetic impurities.
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All authors Chunxiang Wu, Shuijin Chen, Tingyu Zhou, Le Liu, Xin Peng, Jianjian Jia, Xinyu Yu, Hangdong Wang, Jinhu Yang, Jianhua Du, Minghu Fang
Soft Condensed Matter
Linear poroelastic response of thin permeable gel films
Caroline Kopecz-Muller, Joshua D Mcgraw and Thomas Salez
When a hydrophilic and deformable porous material is immersed in a bath, it may absorb the solvent and expand by several times its volume, thus forming a highly soft and porous hydrogel. A stress applied on the soft hydrogel surface deforms it and forces the absorbed solvent to move by flowing through the network of pores. This coupled phenomenon sets the framework of poroelasticity. Moreover, polymeric gels are often used in ultra-thin coatings to tune surface properties. Together with the characteristic poroelastic coupling, this thinness challenges the modelling of their response. In this article, we derive the point-force mechanical response of a thin, permeable and poroelastic layer bounded to a rigid substrate. We show that the gel surface is only deformed around the indentation point, within a radius on the order of the layer thickness. The obtained Green's function can be directly used to predict the space- and time-dependent surface deformation of the gel. Our findings are relevant for a broad range of applications, such as indentation experiments on swollen gels, thin membranes or soft and living systems, as well as lubrication problems involving a soft and porous wall, for instance in microfluidics.
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Materials Science
Geometry-Based Neural-Network Prediction of Electron Localization Function Topology in Dense Hydrogen
Xiaoyu Wang, Miriam Marqués, Sergio Gómez et al. (+3 more)
We develop a machine-learning framework to predict the electron localization function (ELF) of pure, dense hydrogen directly from atomic geometry, bypassing explicit electronic-structure calculations. Trained on first-principles data spanning multiple pressure regimes in dense fluid hydrogen, the model achieves high accuracy ($R^2 > 0.99$) and faithfully reproduces the global distribution of the ELF. A combined real- and reciprocal-space analysis reveals that the residual error is dominated by smooth, long-wavelength components with correlation lengths exceeding typical H–H bonding scales, and that the magnitude of these components increases systematically with pressure. Despite being trained exclusively on dense fluid hydrogen networks, the model transfers robustly to crystalline hydrogen configurations, preserving key features of ELF
topology, including critical points and hydrogen-network connectivity. Taken together, these results suggest a viable route toward geometry-based, high-throughput evaluation of hydrogen-networking characteristics in both fluid and crystalline hydrogen.
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All authors Xiaoyu Wang, Miriam Marqués, Sergio Gómez, Francesc Serratosa, Eva Zurek, Julia Contreras-García
Materials Science
A Theoretical Investigation of the Thermal and Photochemical Mechanisms of Ethylbenzene Dehydrogenation on Rutile TiO$_{2}$(110)
Nico Yannik Merkt
This master's thesis investigates the thermal and photochemical dehydrogenation of ethylbenzene (EB) to styrene on the rutile TiO$_{2}$(110) surface. A dual-methodological
quantum chemical approach is used for this investigation. While industrial styrene production is energy-intensive, photocatalysis on
semiconductor materials offers a promising alternative under significantly milder conditions. To elucidate the underlying mechanisms, this study employs density functional theory (DFT-PBE-D3) for geometry optimization and high-level multi-reference methods (SA-CASSCF) to accurately describe the electronic complexity of excited states and radical intermediates. The investigation reveals that, on the stoichiometric surface, both thermal and photochemical pathways are dominated by
proton-coupled electron transfer (PCET). The wavelength dependence observed in the literature is explained by how the system navigates electronic
manifolds. 343 nm irradiation leads to rapid relaxation into the ground state, where high kinetic barriers persist. In contrast, 257 nm excitation enables the system to persist in higher excited states (S1/T2). This allows the reaction to bypass the rate-determining ground-state barrier. Furthermore, the study demonstrates that surface oxidation causes a fundamental mechanistic shift. On oxidized surfaces, pre-adsorbed oxygen radicals (O$_{Ti}$) enable direct hydrogen atom transfer (HAT), which is more efficient than PCET on reduced surfaces. This "hydrogen scavenger" effect explains the significant increase in styrene yield. This work underscores the necessity of multi-reference treatments for complex surface reactions and provides a fundamental understanding of how surface stoichiometry and
photon energy govern photocatalytic efficiency.
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Materials Science
Polaron Conductivity in $\alpha$-Fe2O3 Quenched by Adsorbed NO2
Tushar K. Ghosh, Elvar Ö. Jónsson, Stephan Steinhauer et al. (+2 more)
Polaron-mediated charge transport in {\alpha}-Fe2O3 plays a central role in its performance as a gas-sensing material, yet the atomistic interaction between surface adsorbates and polarons remains insufficiently understood. Here, density functional theory with Hubbard-U correction (DFT+U) combined with nudged elastic band calculations is used to investigate polaron formation, migration, and quenching at the Fe-terminated {\alpha}-Fe2O3 (0001) surface. The calculated activation energy for small-polaron hopping in bulk {\alpha}-Fe2O3 is found to be 0.12 eV, in excellent agreement with experimental measurements, confirming the validity of the computational approach. Slab calculations show that migration of the polaron from bulk to the surface lowers the energy by 0.12 eV, indicating preferential localization of charge carriers at the gas-solid interface. Adsorption of NO2 induces substantial electron transfer (0.72 e-) from the
oxide to the molecule, eliminating the localized Fe2+ polaron state and thereby suppressing polaronic conductivity. These results provide a direct microscopic explanation for the resistance increase of hematite-based sensors upon exposure to oxidizing gases. More broadly, the study establishes how surface adsorption can modulate charge transport {\alpha}-Fe2O3 through control of polaron populations, offering design principles for improved iron
oxide gas sensors.
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All authors Tushar K. Ghosh, Elvar Ö. Jónsson, Stephan Steinhauer, Panagiotis Grammatikopoulos, Hannes Jónsson
Soft Condensed Matter
A Category-Theoretic Framework from Biological Mechanics to Engineered Stimulus-Response Systems
Lee Marom, Skylar Tibbits, Gioele Zardini et al. (+1 more)
Natural materials achieve adaptive behavior through hierarchical organization and coupled mechanisms across scales. Their translation into engineering, however, remains largely heuristic. What is missing is a formal translation framework that carries biological design logic into engineered realization while preserving physical consistency across levels of abstraction. Here we present a category theoretic compositional framework for verified nature-derived design. The framework defines a category of stimulus response dynamical systems with natural and artificial subcategories. It introduces a structure preserving implementation functor from biological mechanics to engineered systems. It also formalizes a machine agnostic specification layer that links behavioral intent to executable fabrication programs. We instantiate the framework on the hygromorphic pinecone hierarchy as a representative biological case. We implement the full pipeline in Grasshopper, where formal specifications are translated into modular parametric scripts that preserve the compositional structure of the model. The resulting designs are fabricated by fused filament fabrication, evaluated experimentally, and tested against model predictions derived from the pipeline. The current implementation generates four actuator classes spanning two stimulus types and two kinematic responses. One actuator arises purely through composition from previously validated components, without additional manual derivation. The results show that compositionality can function not just as a descriptive
language, but as a generative and system level verifiable method for mechanical material design. More broadly, the work provides a concrete route for
embedding formal multiscale
reasoning within increasingly computational, generative, and physics-driven design workflows.
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All authors Lee Marom, Skylar Tibbits, Gioele Zardini, Markus J. Buehler
Materials Science
Molecular Dynamics simulations of Al-Ti metallic alloy melts using a transferable machine-learning potential
Yuna Kato, Jürgen Brillo, Dirk Holland-Moritz et al. (+4 more)
We investigate the structural and dynamical properties of binary aluminum-titanium
liquid metallic
alloys, as a function of temperature and composition. We make use of MD-simulations, using a transferable machine-learning potential developed by Song et al. [Nature Communications 15, 10208 (2024)], and compare our results to experimental data. Although this potential was initially trained on solid properties, we find good agreement between the experimental data and the simulation results for the
liquid state. The excess volume and compositional changes of the structure are captured well by the machine-learned potential. The simulation allows to disentangle local packing from chemical-ordering effects; the latter are found to be weak in Al-Ti. Dynamical quantities like the viscosity and the
diffusion coefficients are also discussed.
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All authors Yuna Kato, Jürgen Brillo, Dirk Holland-Moritz, Fan Yang, Thomas C. Hansen, Thomas Voigtmann, Linnea Heitmeier
Mesoscale and Nanoscale Physics
Voltage-Regulated Photoluminescence Modulation in a 0D-2D Mixed Dimensional Heterostructure
S. V. U. Vedhanth, Amit Bhunia, Mohit Kumar Singh et al. (+3 more)
Bias dependent oscillations in excitonic photoluminescence are observed in a mixed dimensional 0D 2D
heterostructure. These oscillations arise from modulation by oscillatory DC photocurrent, which exhibits periodic negative differential resistance, indicating recurring charge accumulation within the
heterostructure. The persistence of these oscillations across a macroscopic area of diameter around 200 microns suggests the presence of periodically correlated
quantum phenomena over large length scales. Furthermore, bias dependent oscillations in the photo capacitance are observed, reflecting a periodic ordering and disordering of excitonic populations. Together, these observations point to a direct competition between coherent and incoherent electron tunnelling processes. The coupled oscillatory behaviour of photoluminescence, photocurrent, and photo capacitance highlights new opportunities for
exciton-based
quantum optoelectronic devices.
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All authors S. V. U. Vedhanth, Amit Bhunia, Mohit Kumar Singh, Yuvraj Chaudhry, Mohamed Henini, Shouvik Datta
Soft Condensed Matter
Coexistence of patterned phases in chemically active multicomponent mixtures
Chengjie Luo, Yicheng Qiang, Guido L. A. Kusters et al. (+1 more)
Chemically active mixtures exhibit complex patterns that emerge from the interplay of physical interactions and reactions among components. Individually, these two processes are well-understood: Physical interactions can give rise to phase separation, whereas reactions can form reaction-
diffusion patterns. To understand the combination of both processes, we identify a Lyapunov functional for a class of chemical reactions. By minimizing this functional, we identify a generalized Gibbs phase rule that governs the number of coexisting patterns, and we demonstrate that complex patterns can be created by the modular combination of independent phases. Our theory unveils complex stationary patterns in chemically active mixtures and provides a framework for analyzing more complex systems.
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All authors Chengjie Luo, Yicheng Qiang, Guido L. A. Kusters, David Zwicker
Mesoscale and Nanoscale Physics · Cross-listed from nlin.PS
Turing patterns on non-fluctuating surfaces under mechanical stresses
Fumitake Kato, Hiroshi Koibuchi, Madoka Nakayama et al. (+2 more)
This paper presents a numerical study of Turing patterns (TPs) governed by reaction
diffusion equations for the activator $u$ and the inhibitor $v$ on two- and three-dimensional
lattices without vertex fluctuations. In this framework, $u$ and $v$ are fixed at discrete spatial locations, as pigment
cells on zebrafish skin or shell patterns. Mechanical effects are incorporated through the Finsler geometry modeling formulation, which introduces an internal degree of freedom, $\vec{\tau}$, representing the direction of mechanical stress. A tensile-stress formula based on the Gaussian bond potential is shown to be well defined on non-fluctuating
lattices, enabling the
entropy associated with stress relaxation to be evaluated in a manner analogous to that on fluctuating surfaces. The results indicate that biological TPs respond to external mechanical forces in much the same way as TPs on fluctuating membranes. Simulation codes are provided in the Supplementary Material.
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All authors Fumitake Kato, Hiroshi Koibuchi, Madoka Nakayama, Sohei Tasaki, Tetsuya Uchimoto
Soft Condensed Matter
A Thermodynamic Analysis of Enhanced Metastability in Isochoric Supercooled Liquids
Boris Rubinsky
Experiments show that isochoric (constant-volume) conditions enhance supercooling stability relative to isobaric (constant-pressure) conditions. Here, combining Helmholtz
equilibrium thermodynamics with a first-order perturbation methodology, we derive an inequality governing nucleation stability under volumetric constraint. The derivation provides a general thermodynamic proof that for any substance undergoing phase transformation in which the solid is less dense than the
liquid, the Helmholtz driving force for solidification in isochoric systems is smaller than the Gibbs driving force in isobaric systems. Since nucleation rates depend exponentially on the inverse square of the driving force, this provides a thermodynamic basis for the observed suppression of nucleation rates. While a full
stochastic treatment is beyond the scope of this work, the reduction in driving force implies a weakening of the bias toward growth of pre-critical fluctuations, increasing their probability of thermal dissolution. The analysis yields a dimensionless isochoric stability number. This number is computable from bulk thermodynamic data alone and provides a geometry-independent criterion for comparing metastable
liquid stability across materials and conditions.
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Mesoscale and Nanoscale Physics
Strain and Twist Engineering of Interfacial Thermal Transport in Homo- and Hetero-Interfaces of Graphene and Hexagonal Boron Nitride
Wenwu Jiang, Huasong Qin, Yilun Liu et al. (+3 more)
A dramatic difference between the vertical thermal conductance response of homogeneous and heterogeneous
graphene/h-BN interfaces to external mechanical perturbations, is predicted. Homogeneous
graphene and h-BN interfaces exhibit strong conductance reduction for both in-plane strain and interfacial twist. Conversely, the vertical thermal conductance of the heterogeneous
graphene/h-BN junction is insensitive to twist deformations but shows significant increase or decrease under compressive or tensile strains, respectively. Our atomistic simulations predictions are rationalized by
Fermi's golden rule and density of
phonon modes analyses, indicating that vertical
phonons and local stacking configurations have a central role in the interlayer heat transport behavior. A simple phenomenological model, based on local interlayer distance and stacking, captures well the dependence of vertical heat conductance on strain and twist deformations.
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All authors Wenwu Jiang, Huasong Qin, Yilun Liu, Wengen Ouyang, Oded Hod, Michael Urbakh
Materials Science
Accelerated Prediction of Surface Stability and Particle Morphology in Ionic Crystals via Electrostatic Screening
Sourav Baiju and Payam Kaghazchi
This work presents a fast and scalable approach for predicting surface stability and
equilibrium crystal morphology in ionic materials using electrostatic analysis. The method constructs stoichiometric slab terminations and evaluates their electrostatic energies, enabling high-throughput screening of surface configurations at a fraction of the cost of conventional approaches. Polar surfaces are identified through surface dipole moment calculations and stabilized via electrostatics-based reconstruction using replica-exchange Monte Carlo simulations. The surface dipole moment further emerges as an effective descriptor to distinguish the behavior of different classes of materials. By bypassing expensive Density Functional Theory (DFT) calculations, the approach extends naturally to large systems and high-index surfaces that are typically inaccessible to DFT. Electrostatic interactions are shown to capture the dominant trends in relative surface stability across diverse material systems. The method is validated on simple and complex 3D materials as well as 2D layered
oxides, where the predicted dominant facets are consistent with reported density functional theory and experimental observations. Importantly, the framework also reveals cases where high-index surfaces play a non-negligible role in the
equilibrium morphology. These results establish electrostatics as a fast and reliable route for high-throughput prediction of surface stability and particle morphology, opening a pathway for accelerated materials discovery and providing a robust starting point for more detailed calculations in complex energy materials.
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Other Condensed Matter
Dispersion Splitting of Phonon Polaritons in van der Waals Heterostructure
Daeho Noh, Jaehyeong Ock, Sergey G. Menabde et al. (+1 more)
The biaxial van der Waals
crystal {\alpha}-phase molybdenum trioxide ({\alpha}-MoO3) supports
hyperbolic phonon-polaritons with anomalous dispersion in the Type-I Reststrahlen band (RB-I). Despite the low loss and long lifetime of these polaritons, dispersion engineering in this regime has remained largely unexplored. In this work, we show that when two {\alpha}-MoO3 slabs are placed in close proximity, their eigenmodes hybridize and the dispersion splits into two branches with different momenta and field
symmetry, providing a powerful platform for dispersion manipulation. We experimentally demonstrate the polaritonic mode splitting in {\alpha}-MoO3 within a
heterostructure with hexagonal boron nitride (hBN) employed as a spacer, probed by a scattering-type scanning near-field optical microscope. Furthermore, we propose a design framework for active and mode-selective tailoring of the polaritonic dispersion in the
heterostructure incorporating
graphene, achieved through tuning its
Fermi energy. Our work experimentally demonstrates the feasibility of
phonon-polariton mode splitting in the RB-I and suggests a new platform for dispersion engineering of
hyperbolic phonon-polaritons in general.
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All authors Daeho Noh, Jaehyeong Ock, Sergey G. Menabde, Min Seok Jang
Materials Science
Influence of strain on the anomalous Hall and Nernst effects in Fe thin films
Ao Nakagawa, Ryo Toyama, Keisuke Masuda et al. (+6 more)
The anomalous
Hall effect (AHE) and anomalous Nernst effect (ANE) are the transverse transport phenomena in
magnetic materials, which reflect the Berry
curvature arising from the electronic structure near the
Fermi level.
Lattice strain provides a direct means to tune these effects by modifying the electronic structure; however, disentangling the strain-induced effect through the Berry
curvature modulations in multicomponent materials is challenging due to complexities arising from extrinsic contributions by
impurities and disorder, as well as difficulties in simple direct comparison with first-principles calculations. In this study, we focus on Fe, a prototypical single element ferromagnet with a well-established electronic structure, and tune the sign and magnitude of the strain in epitaxial thin films of by varying the substrates and deposition conditions to investigate the strain effect on the AHE and ANE. Scaling law analysis revealed that the intrinsic anomalous
Hall conductivity (AHC) exhibits a clear tetragonal distortion (c/a) dependence, in good agreement with theoretical calculations based on Berry
curvature modification. In contrast, the anomalous Nernst conductivity (ANC) shows a pronounced deviation from the theoretical values and markedly different c/a dependence. These results demonstrate a crucial difference in the physical origin between the AHC and the ANC in the Fe films; the AHC is predominantly governed by intrinsic mechanisms, whereas the ANC is strongly influenced by the extrinsic contribution.
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All authors Ao Nakagawa, Ryo Toyama, Keisuke Masuda, Weinan Zhou, Hirofumi Suto, Kodchakorn Simalaotao, Yoshio Miura, Yuya Sakuraba, Tetsunori Koda
Materials Science
Coexistence of d-Wave Altermagnetism and Topological States in Janus FeSeX (X = S, Te) Monolayers
Alvaro Gonzalez-Garcia, William Lopez-Perez, Paola Pacheco et al. (+2 more)
The interplay between unconventional magnetism and band
topology in two-dimensional materials has emerged as an important theme in condensed matter physics. Here, we present first-principles calculations that reveal the coexistence of d-wave altermagnetism and topological behavior in Janus FeSeX (X = S, Te) monolayers. The chemical asymmetry of the Janus structure breaks both out-of-plane mirror and inversion
symmetries, leading to anisotropic exchange interactions and momentum-dependent
spin splittings even in the absence of
spin-orbit coupling, the defining signature of altermagnetism.
Phonon dispersion analyses confirm the dynamical stability of both compounds, while strain-dependent calculations demonstrate that the magnitude of the altermagnetic exchange splitting ($\Delta_s$) can be efficiently tuned by biaxial strain. When
spin-orbit coupling is included, a finite topological band gap emerges at the
Fermi level, accompanied by quantized
spin Hall conductivity plateaus and nontrivial topological invariants (
spin Chern number = 1, Z2=1). These findings establish FeSeS and FeSeTe as promising two-dimensional platforms for realizing topological altermagnetism and
spin–orbit–driven charge–
spin conversion, thus opening new avenues for low-dissipation spintronic devices.
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All authors Alvaro Gonzalez-Garcia, William Lopez-Perez, Paola Pacheco, Luz Ramirez-Montes, Rafael Gonzalez-Hernandez
Materials Science
All-organic self-separating three-dimensionally nanoarchitected electrochemical energy storage devices
William R. T. Tait, Sriram Murali, Chao-Hua Hsu et al. (+6 more)
This work realizes a three-dimensionally (3D) nanoarchitected, all organic, "self-separating" lithium-ion electrochemical energy storage (EES) device that is cycled as a solid-state full
cell. The device is enabled by a monolithic carbon anode with a co-continuous pore network, derived from the structure direction of resols by an ultra-large molar mass block copolymer (BCP), poly(styrene-block-2-dimethylaminoethyl methacrylate) (SA). Electropolymerization of a single-phase conductive and redox-active material, poly((2,3-dihydrothieno[3,4-b][1,4]dioxin-2-yl)methyl 9,10-dioxo-9,10-dihydroanthracene-2-carboxylate) (PAQEDOT), into the pore space provides the cathode of the
cell. The device is electronically contacted to the relevant electrode network enabled by the co-continuous nature of each electrode. Electrochemical processing via cycling against external lithium in an electrolyte generates a solid electrolyte interphase (SEI) as a separator and lithiates the
cell electrodes, after which the EES device is cycled in the solid state. While the full
cell does not demonstrate high cyclability, the best full
cell demonstrates a discharge capacity of 267 milliamp hours per gram (mAh/g). This work marks, to the best of knowledge of the authors, the first example of an all-organic materials derived 3D nanoarchitected EES device, as well as the first design of "self-separating"
cell fabrication. Furthermore, generalization of the design to another co-continuous carbon form factor is demonstrated.
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All authors William R. T. Tait, Sriram Murali, Chao-Hua Hsu, Jantakan Nedsaengtip, Christina Lee, R. Paxton Thedford, Vibha Kalra, Joerg G. Werner, Ulrich B. Wiesner
Statistical Mechanics
Complex first-passage transport in ring networks with long-range jumps and stochastic resetting
Oscar Ivan Torres Mena and Francisco J Sevilla
The transport properties of discrete-time random walks on ring networks with deterministic shortcuts are investigated through analytical and numerical methods. The network consists of a periodic chain where each node is connected to its nearest neighbors and to nodes located at a fixed distance $r$. Using the spectral properties of the transition
matrix, we derive explicit expressions for the occupation probabilities and mean first-passage times (MFPTs). Contrary to the common expectation that shortcuts monotonically enhance transport, we find that the MFPT between distant nodes develops a highly non-monotonic dependence on the shortcut length. Beyond a threshold value, the MFPT landscape exhibits a hierarchy of maxima and minima organized in a self-similar pattern associated with commensurability relations between the shortcut length and the system size. The scaling behavior of these extrema reveals regimes where transport efficiency is either strongly enhanced or suppressed. We further analyze the mean squared displacement and the influence of
stochastic resetting, showing that resetting amplifies the oscillatory MFPT structure and induces strongly nonuniform stationary distributions. These results demonstrate that the spatial organization of long-range connections plays a crucial role in determining transport efficiency in networks.
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Statistical Mechanics · Cross-listed from hep-th
Functional Dimensional Regularization for O(N) Models
P. Beretta and A. Codello
The novel functional dimensional regularization (FDR) scheme has proven capable of yielding results that are competitive with the state-of-the-art in the computation of critical exponents in $d=3$, while also reproducing those from the $\varepsilon$-expansion for the Ising and other universality classes. In this work, we show that this is not a mere coincidence: by applying the scheme to the $O(N)$ universality class, we explicitly derive the flow equations and obtain critical exponents that are comparable to those obtained with higher-order non-perturbative approaches. In this case, FDR retains the features already highlighted in previous works – namely, its efficiency and rapid convergence.
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Superconductivity
From Wavefunction Collapse to Superconductivity: Evolution of the Electronic State in Compressed GaNb4Se8
Yuejian Wang, Zhongyan Wu, K C Bhupendra et al. (+5 more)
Understanding how electronic transport evolves from localized to itinerant regimes in correlated cluster solids remains an important challenge in condensed-matter physics. Here we investigate the pressure-dependent transport properties of the lacunar spinel GaNb4Se8, a cluster Mott
insulator at ambient conditions. At low pressures, the resistivity follows Efros-Shklovskii variable-range hopping, indicating Coulomb-gap-controlled carrier localization (x ~ 6.1 Angstrom). A crossover toward metallic transport begins near ~ 5 GPa, whereas a crystallographic transition from the cubic phase to a monoclinic C2 phase occurs at significantly higher pressure (~ 20 GPa), establishing a hierarchy characterized by the decoupling of electronic delocalization from structural
symmetry change. At higher pressures, superconductivity (xi(0) ~ 80-90 Angstrom) emerges from the correlated metallic regime. These results identify GaNb4Se8 as a platform for studying correlation-controlled transport
evolution in cluster-based solids.
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All authors Yuejian Wang, Zhongyan Wu, K C Bhupendra, Dongzhou Zhang, Lin Wang, Sanjay V. Khare, Lilian Prodan, Vladimir Tsurkan
Soft Condensed Matter
Viscous Settling of Bravais Unit-Cells
Sebastian Bürger, Harshit Joshi, S Ganga Prasath et al. (+2 more)
We study experimentally and theoretically the Stokesian settling of a well-known class of porous shapes: Bravais
lattice unit-
cells, whose porosity we vary controllably by changing their
lattice spacing. In our experiments, conducted in a square cuboidal container with its long-axis aligned along
gravity, we find that the settling speed U and the solid fraction {\phi} of these
lattice units obey a power-law relationship U $\propto$ {\phi}^{\gamma} , with an exponent {\gamma} = 0.43 independent of their shape. To understand the observed scaling exponent, we analytically and numerically investigate the settling of the simple cubic structure under different approximations. We find that the walls of the container, though far from the sinking object, have a defining effect. Our Stokesian boundary integral simulations show that the Faxen's boundary correction captures the wall-effects accurately and enables us to discount the wall-effect from the experimental data, yielding a power-law exponent {\gamma} = 0.30 for settling in an unbounded domain. The power-law relating sinking speed and porosity is a step towards predictively understanding the sedimentation fluxes of complex objects in the clouds and the oceans. However, the applicability of this universal scaling to irregular and biologically richer aggregates found in nature remains an open direction.
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All authors Sebastian Bürger, Harshit Joshi, S Ganga Prasath, Rahul Chajwa, Rama Govindarajan