Materials Science
Phase field as a front propagation method for modeling grain growth in additive manufacturing
Murali Uddagiri, Pankaj Antala and Ingo Steinbach
A mesoscopic grain-envelope model applying a phase-field front-propagation method is developed to simulate grain growth under additive manufacturing process conditions. The envelope represents the outer surface of dendritic grains through a diffuse interface. While a modified heat-conduction model that incorporates moving heat sources and latent-heat release provides the
evolution of local thermal field. Envelope propagation is determined from microscopic-solvability-based kinetic law. The model is validated through two- and three-dimensional simulations and subsequently applied to examine the influence of material and process parameters on microstructure
evolution. The results demonstrate that the proposed mesoscopic model offers an efficient and predictive approach for modeling grain growth during multi-pass and multi-layer build-up in additive manufacturing.
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Mesoscale and Nanoscale Physics
Casimir-Polder energy landscape: Unipolarizable atom and ring
Niranjan Warnakulasooriya, John Joseph Marchetta, Prachi Parashar et al. (+1 more)
The Casimir-Polder interaction energy between a unipolarizable point atom and a unipolarizable dielectric ring has been limited, until now, to the case when the atom is confined on the axis of
symmetry of the ring. We find the generalized analytical expression for any position of the atom relative to the ring in terms of complete
elliptic integrals. This is aided by the construction of a class of integrals of a Jacobian
elliptic function as a linear combination of complete
elliptic integrals. Our expression for the interaction energy allows us to investigate the instability of the atom even for the
equilibrium points which exists off the axis of
symmetry.
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All authors Niranjan Warnakulasooriya, John Joseph Marchetta, Prachi Parashar, K. V. Shajesh
Materials Science
OrgFlow: Generative Modeling of Organic Crystal Structures from Molecular Graphs
Mohammadmahdi Vahediahmar, Matthew A. McDonald and Feng Liu
Crystal structure prediction is a long-standing challenge in materials science, with most data-driven methods developed for inorganic systems. This leaves an important gap for organic
crystals, which are central to pharmaceuticals,
polymers, and functional materials, but present unique challenges, such as larger unit
cells and strict chemical connectivity. We introduce a flow-matching model for predicting organic
crystal structures directly from molecular graphs. The architecture integrates molecular connectivity with periodic boundary conditions while preserving the
symmetries of crystalline systems. A bond-aware loss guides the model toward realistic local chemistry by enforcing distributions of bond lengths and connectivity. To support reliable and efficient training, we built a curated
dataset of organic
crystals, along with a preprocessing pipeline that precomputes bonds and edges, substantially reducing computational overhead during both training and inference. Experiments show that our method achieves a Match Rate more than 10 times higher than existing baselines while requiring fewer sampling steps for inference. These results establish generative modeling as a practical and scalable framework for organic
crystal structure prediction.
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Superconductivity
Insight into high-entropy effect in body-centered cubic superconducting alloys
Hanabusa Senga, Yuto Watanabe, Fubuki Iwase et al. (+6 more)
We have characterized the superconducting critical temperature ($T_\mathrm{c}$), the Debye temperature ($\theta_\mathrm{D}$), the electronic specific heat coefficient, and the Vickers microhardness of HfNbTiVZr, NbTiZr, HfNbTi, HfNbZr, and HfNbTa, all possessing a body-centered cubic (bcc) structure. By compiling a comparable
dataset for other equiatomic quinary bcc high-
entropy alloy (HEA)
superconductors, we have examined the validity of the hypothesis regarding the high-
entropy effect in bcc HEA
superconductors, as proposed in our previous work. This hypothesis attributes the observed negative correlation between the electron-
phonon coupling constant ($\lambda_\mathrm{e-p}$) and $\theta_\mathrm{D}$ to a reduced
phonon lifetime at higher $\theta_\mathrm{D}$, arising from the uncertainty principle in highly disordered quinary
alloys. However, a pronounced change in this negative correlation is not evident in equiatomic ternary
alloys with a lower degree of atomic disorder, thereby providing limited support for the hypothesis. Alternatively, by assembling the full
dataset of bcc
alloys spanning binary through senary systems, we have identified a universal negative correlation between $\lambda_\mathrm{e-p}$ and $\theta_{D}$. This result would be useful for the materials design of bcc superconducting
alloys. We further propose that the Vickers microhardness offers an alternative means to evaluate $\theta_{D}$ and may serve as a rapid screening metric for identifying bcc
alloys with desired properties.
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All authors Hanabusa Senga, Yuto Watanabe, Fubuki Iwase, Ryo Masuda, Daichi Kawahara, Toshiki Haruyama, Terukazu Nishizaki, Yoshikazu Mizuguchi, Jiro Kitagawa
Superconductivity
Enhanced $T_\mathrm{c}$ in eutectic high-entropy alloy superconductors Hf-Nb-Sc-Ti-Zr
Issei Kubo, Yuto Watanabe, Shuma Kawashima et al. (+4 more)
The present investigation into the superconducting properties of eutectic high-
entropy alloy (HEA) Hf-Nb-Sc-Ti-Zr systems reveals an enhanced superconducting critical temperature ($T_\mathrm{c}$) in body-centered cubic (bcc) phases compared to typical quinary bcc HEAs. In Hf$_{10}$Nb$_{25}$Sc$_{25}$Ti$_{20}$Zr$_{20}$, Hf$_{5}$Nb$_{45}$Sc$_{20}$Ti$_{15}$Zr$_{15}$, and Hf$_{5}$Nb$_{45}$Sc$_{10}$Ti$_{5}$Zr$_{35}$ systems, which span a broad range of valence electron concentration per atom,
lattice strain and the presence of partial or absent eutectic phases are characteristic features at lower annealing temperatures. The eutectic regions expand rapidly following annealing at 600$^{\circ}$C in all systems. The $T_\mathrm{c}$ of each system increases markedly with rising annealing temperatures from 400$^{\circ}$C to 600$^{\circ}$C, reaching a maximum value of 9.93 K in the Hf$_{5}$Nb$_{45}$Sc$_{10}$Ti$_{5}$Zr$_{35}$ sample annealed at 800$^{\circ}$C. Nearly all samples can be classified as strong-coupling
superconductors. The sample annealed at 500$^{\circ}$C in the Hf$_{5}$Nb$_{45}$Sc$_{10}$Ti$_{5}$Zr$_{35}$ system exhibits a critical current density ($J_\mathrm{c}$) exceeding the practical threshold of 10$^{5}$ A/cm$^{2}$ up to approximately 4 T at 4.2 K and 6 T at 2 K. The elevated $J_\mathrm{c}$ is attributed to significant
lattice strain and phase instability. The underlying mechanism for the enhanced $T_\mathrm{c}$ in Hf-Nb-Sc-Ti-Zr systems is examined through specific heat data analysis, suggesting that the expansion of the eutectic regions induced by thermal annealing plays a pivotal role.
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All authors Issei Kubo, Yuto Watanabe, Shuma Kawashima, Tomohiro Miyaji, Yoshikazu Mizuguchi, Terukazu Nishizaki, Jiro Kitagawa
Materials Science
Dual energy-differentiated topological transition in artificial red phosphorus chains
Vít Jakubský, B. Manjarrez-Montañez, Rafael A. Méndez-Sánchez et al. (+1 more)
We investigate the spectral and transport properties of an atomic chain of red phosphorus. We reveal the separation of flat-band states from the rest of the system and calculate its energy bands analytically. The topological properties of the system are established through the evaluation of the Berry (Zak) phase of the energy bands, revealing nontrivial
topology. The Berry phase depends on the relative strength of the hopping parameters and exhibits dual energy-dependent topological phase transitions. Remarkably, the emergence of inert band edges provides a direct spectral signature of these transitions, acting as energy-resolved indicators of the redistribution of topological charge between bands. The existence of the associated edge states is proved numerically for finite
lattices. The theoretical predictions, particularly the band structure and the existence of edge states, are further confirmed by numerical simulations of red phosphorus through a phononic
lattice in the form of a highly structured aluminum plate.
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All authors Vít Jakubský, B. Manjarrez-Montañez, Rafael A. Méndez-Sánchez, Yonatan Betancur-Ocampo
Soft Condensed Matter · Cross-listed from physics.flu-dyn
Squirmers with arbitrary shape and slip: modeling, simulation, and optimization
Kausik Das, Hai Zhu, Marc Bonnet et al. (+1 more)
We consider arbitrary-shaped microswimmers of spherical
topology and propose a framework for expressing their slip velocity in terms of tangential basis functions defined on the boundary of the swimmer using the Helmholtz decomposition. Given a time-independent slip velocity profile, we show that the trajectory followed by the microswimmer is a circular helix. We derive analytical expressions for the translational and rotational velocities of a prolate spheroid swimmer in terms of its Helmholtz decomposition modes and explore the effect of aspect ratio on these rigid body velocities. Then, for a given arbitrary swimmer shape of spherical
topology, we investigate which slip profile minimizes the total power loss. A partial minimization is performed in which the direction of net motion of the swimmer is prescribed, followed by a global optimization procedure in which the best net motion direction is determined. The optimization results suggest that the competition between linear and rotational optimal motion is linked to
symmetries in the shape of the microswimmer.
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All authors Kausik Das, Hai Zhu, Marc Bonnet, Shravan Veerapaneni
Soft Condensed Matter
On the anomalous elasticity in the mechanical response of amorphous solids
Gilles Tarjus, Misaki Ozawa and Giulio Biroli
The response of amorphous solids to a mechanical perturbation consists in an elastic and a plastic deformation. The latter is mediated by localized irreversible rearrangements associated with Eshelby-like quadrupolar singularities in the displacement field. It has recently been argued that a density of such singularities leads to an anomalous elastic behavior taking the form of screening effects, which goes beyond classical elastic predictions. Here, we reexamine this scenario using general theoretical arguments and a description in terms of an elasto-plastic model, which we compare with atomistic simulations of the canonical Eshelby inclusion geometry. We discuss the conditions under which a finite, i.e., nonvanishing, density of quadrupolar events is created by an imposed perturbation. We argue that, except when the perturbation is macroscopic, there are many situations in which the density of quadrupolar defects is zero in the thermodynamic limit. In these cases, we find that plastically active quadrupoles emerge in a region whose size generically scales as the spatial extent $\ell$ of the mechanical perturbation. This mechanism leads to anomalous elasticity on a scale $\ell$ close to the perturbation and to conventional elasticity beyond. The simulations of the elasto-plastic model reproduce the emergence of plastic quadrupoles in a region set by $\ell$ and the associated renormalization of the effective shear modulus, but they do not exhibit the dipole-screening signatures reported in atomistic and experimental studies. Our analysis delineates the scale-dependent breakdown of long-wavelength elasticity in amorphous materials and suggests directions for incorporating anomalous screening into mesoscopic modeling frameworks.
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Statistical Mechanics · Cross-listed from quant-ph
Self-correction phase transition in the dissipative toric code
Sanjeev Kumar and Hendrik Weimer
We analyze a time-continuous version of a cellular automaton decoder for the toric code in the form of a Lindblad master equation. In this setting, a self-correcting
quantum memory becomes a thermodynamical phase of the steady state, which manifests itself through the steady state being topologically ordered. We compute the steady state phase diagram, finding a competition between the error correction rate and the update rate for the classical field of the cellular automaton. Strikingly, we find that self-correction of errors is possible even in situations where conventional
quantum error correction does not have a finite threshold.
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Materials Science
Unraveling the temperature-responsive charge-disproportionation in BaBiO$_3$
Sumit Sarkar, Priyanka Yadav, Sourav Chowdhury et al. (+2 more)
This study shows that the charge disproportionation at the Bi site in BaBiO$_3$ alters as a function of temperature. Decreasing the temperature from 300K down to 160K leads to a significant modification of the density of states corresponding to the Bi-O hybridized band near the
Fermi level (E$_\text{F}$). This modification indicates reduction of Bi 6$sp$ - O 2$p$ hybridization and O 2$p$ spectral weight near E$_\text{F}$. The strong decrement of covalency at lower temperatures is accompanied by a decrement in O 2$p$ hole density due to possible charge transfer from Bi 6$s$ to the O 2$p$ band. Bi-charge state analysis from Bi-4$f$ core-level spectra showed that at 300K, $\delta$ (charge difference between alternate Bi sites) value in 4$\pm\delta$ is much less than at 160K, which reveals the transition towards the ionic nature of CD or static CD in BBO at low temperature. On the other hand, O 1$s$ core-level spectra displayed an asymmetric shape, and temperature-dependent modifications of the asymmetric shape and intensity have been observed. This highlights the significant influence of the O 2$p$ band hole on the dynamical CD at the Bi site.
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All authors Sumit Sarkar, Priyanka Yadav, Sourav Chowdhury, Rajamani Raghunathan, Ram Janay Choudhary
Superconductivity
Nearly twofold overestimation of the superconducting volume fraction in pressurized Ruddlesden-Popper nickelates
Aleksandr V. Korolev and Evgeny F. Talantsev
The detection of the DC diamagnetic state in pressurized Ruddlesden-Popper nickelates remained an unsolved experimental problem until recent experiments in which Zhu et al.$^1$ measured the DC diamagnetic responses in zero-field cooled (ZFC) mode in pressurized La4Ni3O10. Zhu et al.$^1$ reported that the ratio of the measured ZFC
magnetic moment to the Meissner
magnetic moment of the sample (and this ratio was termed the superconducting volume fraction$f$) reaches 81-86%. We regard outstanding experimental results$^1$; however, our calculations based on the reported experimental
datasets$^1$ using the standard procedure showed the ratio to be 51-59%. Upon our request, Zhu et al.$^1$ provided detailed explanations and the equation they used to calculate$f$. To our knowledge, the procedure$^1$ and equation$^1$ for calculating $f$ have never been mentioned or described before, including in Ref.$^1$. Here we argue that the proposed equation$^1$ and procedure$^1$ are incorrect, and that this equation$^1$ results in multiple overestimations of the superconducting volume fraction in the sample. This overestimation error affects all superconducting volume fractions $f$ in Ruddlesden-Popper nickelates reported to date$^{1-4}$. Therefore, we describe the error we discovered in this paper.
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Statistical Mechanics · Cross-listed from quant-ph
Entanglement dynamics of many-body quantum states: sensitivity to system conditions and a hidden universality
Devanshu Shekhar and Pragya Shukla
We consider physical
Hamiltonians that can be represented by the multiparametric Gaussian ensembles, theoretically derive the state ensembles for its eigenstates and analyze the effect of varying system conditions on its bipartite
entanglement entropy. Our approach leads to a single parametric based common mathematical formulation for the
evolution of the
entanglement statistics of different states of a given
Hamiltonian or different
Hamiltonians subjected to same
symmetry constraints. The parameter turns out to be a single functional of the system parameters and thereby reveals a deep web of connection hidden underneath different
quantum states.
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Mesoscale and Nanoscale Physics
Dynamics and Pinning for Skyrmions in Altermagnets
J. C. Bellizotti Souza, C. J. O. Reichhardt, A. Saxena et al. (+1 more)
We examine the dynamics,
Hall angle, and pinning for Néel skyrmions in an altermagnet. Using an atomistic model, we show that skyrmion velocity and
Hall angle dependence is anisotropic with respect to the direction of the drive, due to the fourfold
symmetry implied by the two sublattices of the altermagnet. The skyrmion
Hall angle and velocity at fixed drive show strong variations for increasing ratios of the exchange constant of the sublattices, $J_2/J_1$. This fourfold anisotropy of altermagnetic (ATM) skyrmions also leads to anisotropic pinning effects for an ATM skyrmion interacting with isotropic circular pinning sites. We also propose a simple particle model for this system that takes into account this anisotropy and find that it captures both the variations of the ATM skyrmion
Hall angle and velocity as a function of drive direction, as also found in the atomistic simulations. Using this particle model, we examine ATM skyrmions interacting with a periodic array of pinning sites. For increasing ratios of $J_2/J_1$, we find a strongly non-monotonic ATM skyrmion velocity, where there is a minimum in the velocity where the skyrmion locks to different
symmetry directions of the periodic pinning
lattice. For a random array, we find that ATM skyrmions show strongly anisotropic depinning thresholds and velocity responses for different drive directions, and that the
Hall angle is nearly constant with drive. In comparison, for the same parameters, the depinning threshold for a
ferromagnetic (FM) skyrmion is lower, and the skyrmion
Hall angle shows a strong velocity dependence. The lower depinning threshold for FM skyrmions is due to stronger Magnus forces.
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All authors J. C. Bellizotti Souza, C. J. O. Reichhardt, A. Saxena, C. Reichhardt
Soft Condensed Matter
On the Statistical Mechanics of Active Membranes: Some Selected Results
Sreekanth Ramesh, Prashant K. Purohit and Yashashree Kulkarni
Biological membranes and vesicles play a central role in living systems, forming dynamic interfaces that regulate cellular organization and function. Classical descriptions of membrane mechanics that are rooted in
equilibrium statistical mechanics and linear elasticity have yielded deep insights into membrane morphology and the role of thermal fluctuations on cellular function. However, real biological membranes operate far from
equilibrium, continuously driven by active processes powered by energy consuming
proteins. In this work, we employ a nonequilibrium statistical mechanics framework to model active membranes and derive analytical expressions for four fundamental properties that characterize their mechanical behavior: (a) the tension area relation, (b) the mean square amplitude of fluctuations, (c) correlation of normal vectors, and (d) the persistence length. These results collectively highlight the utility of fluctuation spectra as a starting point for elucidating membrane mechanics in both passive and active settings. Moreover, these results provide a theoretical basis for analyzing and interpreting fluctuation based assays of active membrane behavior.
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Mesoscale and Nanoscale Physics · Cross-listed from physics.app-ph
Artificial Neural Network (ANN) – Oscillatory Neural Network (ONN) Hybrid System Using Domain-Wall Synapse Devices and Nano-Constriction Spin Hall Nano Oscillators
Raman Hissariya, Gajjala Venkata Sreekar Reddy, Ashwin Tulapurkar et al. (+1 more)
A coupled spintronic oscillator array has been considered attractive for neuromorphic computing applications. Experimental reports have shown the nano-constriction geometry to be a relatively easier-to-fabricate platform for implementing such
spin oscillators, but most prior reports on training and inference
algorithms for neuromorphic computing using
spin oscillators have been mostly restricted to the nano-pillar geometry. Also, those prior reports involve updating the natural frequency values of the oscillators and moving the synchronization regions on to the data clusters during the offline learning phase, which has associated challenges. In this context, we design and simulate a novel artificial neural network (ANN) - oscillator neural network (ONN)
algorithm where in the offline learning phase, the weight parameters of the ANN are updated such that the data clusters are instead moved to the synchronization regions of
spin Hall nano oscillators (SHNOs) in the nano-constriction geometry, as obtained through micromagnetic simulations. We further simulate the on-chip inference part of the ANN-ONN
algorithm where the ANN is implemented on a crossbar array of domain-wall synapse devices, as simulated here through micromagnetics, and the ONN is implemented on nano-constriction SHNOs. We show successful data classification for both binary and multi-class classification tasks to demonstrate the generalizability of our proposed scheme.
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All authors Raman Hissariya, Gajjala Venkata Sreekar Reddy, Ashwin Tulapurkar, Debanjan Bhowmik
Strongly Correlated Electrons
Microscopic origin of hard-plane antiferromagnetism in the Kondo lattice Ce2Rh3Ge5
Rajesh Tripathi, Ewan Scott, D. T. Adroja et al. (+16 more)
Hard plane
antiferromagnetic order where ordered moments lie perpendicular to the single-ion
crystal electric field easy axis is rare in Ce-based Kondo
lattices and is a subject of active interest. Here we show that Ce$_2$Rh$_3$Ge$_5$ realizes a hard-plane
antiferromagnetic state in which partial delocalization of the local moment gives rise to an RKKY exchange that overturns the single-ion easy-axis preference.
Neutron diffraction reveals moments in the $ab$ plane, while inelastic
neutron scattering and susceptibility establish a
magnetic easy axis along $c$ in the paramagnetic regime, highlighting a clear inversion between single-ion and ordered-state anisotropies. In this work, we establish a unified microscopic framework to consistently account for partial $4f$-moment delocalization, enhanced in-plane RKKY exchange, and the resulting hard-plane
antiferromagnetic order. Ce$_2$Rh$_3$Ge$_5$ thus provides a
benchmark system in which single-ion anisotropy, Kondo screening, and RKKY exchange compete on comparable energy scales, revealing a cooperative route to hard-axis ordering in strongly hybridized Kondo
lattices.
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All authors Rajesh Tripathi, Ewan Scott, D. T. Adroja, D. Das, C. Ritter, Huanzhi Hu, Michal P. Kwasigroch, Nicholas Corkill, Gheorghe Lucian Pascut, T. Masuda, S. Asai, T. Takabatake, T. Onimaru, T. Shiroka, Francis Pratt, A. M. Strydom, S. Langridge, A. Sundaresan, S. Patil
Soft Condensed Matter
Microgel Translocation Through Narrow Capillaries
Subhadip Biswas and Buddhapriya Chakrabarti
The transport of soft viscoelastic gels through confined geometries underlies critical processes in biomedical, biological, and industrial systems. Here, we examine the translocation of a spherical microgel through a narrow capillary whose diameter is smaller than the
equilibrium gel size. Using coarse-grained molecular dynamics simulations in tandem with mean-field theory and mechanical analysis, we uncover a critical threshold diameter $d_c$ below which the microgel cannot enter, regardless of the applied pressure. This
geometric limit emerges from the interplay between gel elasticity and its internal network connectivity, captured quantitatively by a graph-theoretic model. We construct a phase diagram in the parameter space of tube diameter $d$, applied force $f_g$, and gel stiffness $Y$ (Young's modulus), which delineates the regimes of successful translocation and mechanical arrest. Under negligible wall friction, gel mobility scales with the applied force; however, beyond a cutoff set by the network
topology, progressive densification in the constriction stalls the microgel. Our results reveal the mechanical and topological determinants of soft-gel transport in confinement and provide predictive guidelines for engineering gel-based systems in microfluidics, drug delivery, and tissue-level filtration.
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Materials Science · Cross-listed from math-ph
Some effective operators for graphene monolayer superlattices, from variational perturbation theory
Louis Garrigue
Our goal is to provide precise effective operators for monolayer
graphene at
Fermi energy. We consider the microscopic potential created by a
lattice, and add a macroscopic potential with the same periodicity but varying at a scale $\varepsilon^{-1} \in \mathbb{N}$, creating a superlattice. Our approach combines a variational approximation with perturbation theory and a multiscale method. At the effective level the usual massless Dirac operator is enriched by other operators. We provide simulations for
graphene to show the increased accuracy, and a theoretical result proving the improved validity time scale in the dynamical case.
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Materials Science
Specific features of the magnetic-field dependences of electrical resistivity in Bi–Mn solid solutions with low Mn content
A.V. Terekhov, V.M. Yarovyi, Yu.A. Kolesnichenko et al. (+4 more)
For the first time, the field dependences of the magnetoresistance of a textured polycrystalline Bi$_{88.08}$Mn$_{11.92}$ sample were investigated in the $H \perp I$ and $H \parallel I$ configurations, and the results were compared with those previously obtained for the solid solution Bi$_{95.69}$Mn$_{3.69}$Fe$_{0.62}$ with a lower manganese concentration. It was demonstrated that the magnetoresistance field dependencies for Bi$_{88.08}$Mn$_{11.92}$ differ significantly from those of Bi$_{95.69}$Mn$_{3.69}$Fe$_{0.62}$ below 100 K, becoming nearly identical as the temperature approaches room temperature. It was established that the maximum relative magnetoresistance values for Bi$_{88.08}$Mn$_{11.92}$ are observed at a
magnetic field of 90 kOe and a temperature of 100 K in both the $H \perp I$ and $H \parallel I$ configurations, amounting to 3170% and 380%, respectively. These values are significantly lower than those previously reported for the solid solution containing less manganese (Bi$_{95.69}$Mn$_{3.69}$Fe$_{0.62}$), which were 3877% and 742%, respectively. Analysis of the results indicates that differences in field dependence among the studied materials are associated with varying amounts of
magnetic $\alpha$-BiMn. The anomalous magnetoresistance behavior, as compared with that of pure bismuth, is attributed to the influence of internal magnetism on electrical transport within the bismuth
matrix of the studied solid solutions.
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All authors A.V. Terekhov, V.M. Yarovyi, Yu.A. Kolesnichenko, K. Rogacki, E. Lähderanta, E.V. Khristenko, A.L. Solovjov
Materials Science
Constrained Diffusion for Accelerated Structure Relaxation of Inorganic Solids with Point Defects
Jingyi Cui, Jacob K. Christopher, Ankita Biswas et al. (+2 more)
Point defects affect material properties by altering electronic states and modifying local bonding environments. However, high-throughput first-principles simulations of point defects are costly due to large simulation
cells and complex energy landscapes. To this end, we propose a generative framework for simulating point defects, overcoming the limits of costly first-principles simulators. By leveraging a primal-dual
algorithm, we introduce a constraint-aware
diffusion model which outperforms existing constrained
diffusion approaches in this domain. Across six defect configuration settings for Bi2Te3, the proposed approach provides state-of-the-art performance generating physically grounded structures.
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All authors Jingyi Cui, Jacob K. Christopher, Ankita Biswas, Prasanna V. Balachandran, Ferdinando Fioretto
Strongly Correlated Electrons
Precompression engineering of metal-insulator transition and magnetism in designed breathing kagome systems
Qingzhuo Duan, Hongdao Zhuge, Ying Liang et al. (+1 more)
Kagome materials featuring dispersive Dirac cones and topological flat bands exhibit unique electronic and
magnetic properties. However, kagome compounds with tunable electrical conductivity remain scarce, which severely impedes their device applications. Here, based on density functional theory (DFT) and Boltzmann transport theory, we introduce the breathing effect into kagome materials $\mathrm{Nb_3XCl_7}$ (X = F, Cl, Br, I) via chemical precompression, thereby inducing a metal-
insulator transition and
magnetic variation. We determine that the band structures, optical absorption spectra and
magnetic ground states agree well with experimental results at the effective correlation strength $U_{\text{eff}} = 2$ eV. The calculated conductivity and
magnetic properties reveal that the monolayer $\mathrm{Nb_3Cl_8}$ and $\mathrm{Nb_3XCl_7}$ undergoes transitions from paramagnetic metals to Mott
insulators at $U_{\text{eff}} = 1$ eV and $t_{\text{out}}/t_{\text{in}} = 0.6674$, respectively. Our detailed analysis establishes that the stronger breathing effect corresponds to enhanced chemical precompression, which reduces the region of free electron gas between intercell Nb atoms and facilitates the metal-
insulator transition. Finally, we propose several viable synthesis routes for $\mathrm{Nb_3FCl_7}$, $\mathrm{Nb_3BrCl_7}$, and $\mathrm{Nb_3ICl_7}$, providing predictive guidance for experimental studies. Our study establishes a practical framework for investigating the breathing effect in correlated kagome systems and yields valuable insights into the mechanisms underlying metal-
insulator transition and
magnetic properties in real breathing kagome materials.
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All authors Qingzhuo Duan, Hongdao Zhuge, Ying Liang, Tianxing Ma
Soft Condensed Matter
Training overdamped dynamics
Marc Berneman and Daniel Hexner
In regimes where inertia is negligible, the temporal
evolution is governed by overdamped dynamics. This limit is particularly relevant in soft-matter contexts, such as
polymers, colloidal suspensions, and processes occurring at the cellular scale. Being able to manipulate the dynamics of such many-particle systems would enable control over rate-dependent elastic responses, time-dependent material properties, relaxation processes, and perhaps the hydrodynamics of suspensions. In this work, we develop a framework for manipulating overdamped dynamics through local, physically motivated update rules. Our approach is inspired by ideas from physical learning and directed aging, in which microscopic parameters adapt autonomously to endow a material with a desired function. Using the Rayleighian formulation, whose minimization reproduces the overdamped equations of motion, we derive approximate directed-aging and
equilibrium-propagation rules tailored to dissipative systems. To demonstrate these ideas, we study a disordered Maxwell material that behaves elastically at short times but flows at long times. By locally modifying the viscous damping, we show that one can tune the viscous Poisson's ratio and shape local mechanical responses. These results illustrate how materials can be trained to exhibit targeted rate-dependent elastic and viscous behaviors.
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Superconductivity
Superconducting phase diagram of multi-layer square-planar nickelates
Grace A. Pan, Dan Ferenc Segedin, Sophia F. R. TenHuisen et al. (+21 more)
The discovery of superconductivity in square-planar nickelates has offered a rich materials platform to explore the origins of cuprate-like superconductivity. Experimental investigations however have largely been limited to the infinite-layer $R$NiO$_2$ ($R$=rare-earth) nickelates. Here, we construct a phase diagram of multi-layer square-planar Nd$_{n+1}$Ni$_n$O$_{2n+2}$ compounds and discover signatures of superconductivity for $n$ = 4 - 8. Upon decreasing the dimensionality $n$, the superconducting anisotropy evolves due to 4$f$ electron effects, and electronic structure characteristics approach cuprate-like behavior.
Magnetic fluctuations persist from within the superconducting regime and into the over-doped, non-superconducting regime. Remarkably, the superconducting regime overlaps with that of chemically-doped infinite-layer nickelates, demonstrating underlying commonalities and distinct differences across varying structural realizations of square-planar nickelates. Our work establishes this layered template for creating new nickel-based
superconductors.
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All authors Grace A. Pan, Dan Ferenc Segedin, Sophia F. R. TenHuisen, Lopa Bhatt, Harrison LaBollita, Abigail Y. Jiang, Qi Song, Ari B. Turkiewicz, Denitsa R. Baykusheva, Abhishek Nag, Stefano Agrestini, Ke-Jin Zhou, Jonathan Pelliciari, Valentina Bisogni, Hua Zhou, Mark P. M. Dean, Hanjong Paik, David A. Muller, Lena F. Kourkoutis, Charles M. Brooks, Matteo Mitrano, Antia S. Botana, Berit H. Goodge, Julia A. Mundy
Materials Science
Nonperturbative Magnetic Orbital Hall Effect in Altermagnets
Xukun Feng, Jin Cao, Lay Kee Ang et al. (+3 more)
Recent studies on altermagnets have focused considerable
attention on nonrelativistic effects that persist in the absence of
spin-orbit coupling (SOC). As a result, the relative importance of various phenomena in altermagnets has commonly been judged by their dependence on SOC. Here, we challenge this common wisdom by uncovering the
magnetic orbital
Hall effect, which is nonperturbative in SOC strength. We establish the
symmetry properties of this effect, demonstrating that it is strictly forbidden in conventional collinear antiferromagnets yet universally allowed in all ten
spin-Laue classes of collinear altermagnets. Counterintuitively, although SOC-induced, it reaches
giant magnitudes in altermagnets-comparable to or even exceeding the nonrelativistic
spin Hall effect. Moreover, altermagnetic
symmetry enables unconventional collinear-polarized orbital currents, allowing field-free manipulation of perpendicular magnetization. Our first-principles calculations predict strong room-temperature responses in the experimentally established altermagnets CrSb and FeSb2. These findings reveal the previously overlooked potential of altermagnetic orbitronics and broaden the horizons for altermagnets in high-performance
magnetic memory applications.
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All authors Xukun Feng, Jin Cao, Lay Kee Ang, Shengyuan A. Yang, Cong Xiao, X. C. Xie
Mesoscale and Nanoscale Physics
Bridging Quantum and Classical Descriptions of Spin Dynamics in a Dzyaloshinsky-Moriya Trimer
Robert Wieser and Raúl Sánchez Galán
The
spin dynamics of a trimer with Dzyaloshinsky-Moriya (DM) interaction are investigated within a unified
Hamiltonian framework that connects
quantum-mechanical and semiclassical descriptions. The interpolation between the two regimes is realised by solving the modified Gisin-Schrödinger equation, in which the relative weight of a
quantum coherence and local mean-field contributions is continuously tuned. The resulting dynamical behaviour is analysed and summarised in a ground state diagram that illustrates how the character of the
spin motion evolves from fully
quantum to semiclassical as the DM interaction is treated at different levels of approximation. In the last part of the publication, the
chiral spin dynamics proposed by Da-Wei Wang et al. is examined theoretically, taking into account its behaviour at the boundary between
quantum and classical physics.
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Statistical Mechanics
peapods: A Rust-Accelerated Monte Carlo Package for Ising Spin Systems
Yan Ru Pei
We present peapods (github.com/PeaBrane/peapods), an open-source Python package for Monte Carlo simulation of Ising
spin systems with arbitrary coupling constants on periodic Bravais
lattices with user-specified neighbor offsets. The computational core is written in Rust and exposed to Python via PyO3, combining the ergonomic interface of Python with the performance of compiled,
memory-safe code. The package implements Metropolis and Gibbs single-
spin-flip
algorithms, Swendsen-Wang and Wolff cluster updates, parallel tempering, and three replica cluster moves for
spin glasses: the Houdayer isoenergetic cluster move, the Jorg
stochastic variant, and the Chayes-Machta-Redner (CMR) blue-bond
algorithm. Overlap statistics between replica pairs enable computation of the
spin glass order parameter and Binder ratio. Replica-level parallelism is achieved through the Rayon work-stealing scheduler. We validate the implementation against the exact critical temperatures of the two-dimensional Ising model on the square and triangular
lattices via finite-size scaling of the Binder cumulant.
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