Materials Science · Cross-listed from physics.chem-ph
Reactive calcium carbonate precipitation from an atomic cluster expansion potential and enhanced sampling
Eslam Ibrahim, Yury Lysogorskiy, Ralf Drautz et al. (+1 more)
Calcium carbonate formation from aqueous solution is central to biomineralization and to carbon sequestration through mineral carbonation. At near-neutral pH, the process is highly reactive, with
proton transfer mediating the interconversion between carbonate species. Most atomistic simulations to date either treat carbonate speciation as fixed or consider
proton transfer only in small clusters. Here, we combine an ab initio trained atomic cluster expansion (ACE) machine-learning potential for molecular dynamics with enhanced sampling to enable reactive simulations of the early stages of calcium carbonate precipitation at previously inaccessible length and time scales. We study
proton transfer and carbonate speciation in ion pairs and triplets, as well as in the collective aggregation of many ions. Our simulations with few ions show that ion association provides a favorable pathway for
proton transfer, facilitating interconversion between carbonate, bicarbonate, and carbonic acid. In many-ion systems,
proton transfer occurs spontaneously alongside aggregation, and we observe significant changes in the coordination environments as species evolve during the simulations. These results show that ion aggregation and chemical reactivity can be strongly coupled during the early stages of nucleation from solution.
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All authors Eslam Ibrahim, Yury Lysogorskiy, Ralf Drautz, Pablo M. Piaggi
Materials Science
Interplay between Isomerization and Spin Crossover in 1D Fe-Indigo Coordination Polymers on Ag substrates
Ritam Chakraborty, Hongxiang Xu, Biao Yang et al. (+5 more)
Spin-crossover (SCO) compounds offer a route to switchable molecular functionality in reduced dimensions. However, one-dimensional (1D) SCO chains, which offer the possibility to study ligand fields other than the paradigmatic octahedral field, remain comparatively little studied. Here, we use first-principles density functional theory (DFT+$U$) to investigate Fe-indigo coordination-
polymer chains synthesized experimentally on Ag(111) and Ag(100) substrates. These display a rich interplay between changes in ligand field (isomerization) and
spin crossover. On-surface isomerization on Ag(111) interconverts (N,O)-chelated trans configuration and (N,N)-/(O,O)-chelated cis configurations at the Fe centers. The lowest-energy trans and cis solutions on Ag(111) have different
spin configurations over the interval $0.66<U<3.00$~eV. At the reference value $U=1$~eV, the preferred trans solution is the mixed LS–LS–HS configuration, whereas the preferred cis solution is LS–LS–LS. The experimentally observed preference for cis chains on Ag(111) and trans chains on Ag(100) is reproduced for the range $0.88<U<3.75$~eV. To interpret these results, toy models and
spin-resolved Fe $3d$ projected densities of states are used, while freestanding-chain calculations reveal a strain-sensitive LS–HS competition. These results provide a microscopic explanation for isomerization-controlled
spin-state switching in a 1D coordination
polymer.
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All authors Ritam Chakraborty, Hongxiang Xu, Biao Yang, Harshdeep Singh Chhabra, Joachim Reichert, Johannes V. Barth, Anthoula C. Papageorgiou, Shobhana Narasimhan
Disordered Systems and Neural Networks · Cross-listed from quant-ph
Nanoscale magnetometry via collective many-body dynamics in diamond
Haoyang Gao, Piotr Put, Nathaniel T. Leitao et al. (+9 more)
Many-body dynamics constitutes a promising approach for creating correlations between
quantum particles which can be used for applications in sensing and metrology. However, utilizing this potential for substantial gains in practical settings is a challenging task with only a very few applications realized to date. Here, we demonstrate an approach to nanoscale
magnetic sensing enabled by strongly interacting electronic
spins in a room temperature solid. By coherently controlling collective many-body dynamics of a dipolar ensemble of $\sim 10^4$ nitrogen-vacancy (NV) centres in diamond with pulsed
magnetic field gradients, we demonstrate practical metrological gain up to $7.9(2)\,\mathrm{dB}$ for
magnetic signal detection and $8.8(3)\,\mathrm{dB}$ for
magnetic noise sensing, fully accounting for experimental overheads. Finally, we combine these methods to demonstrate a momentum-space-resolved sensing modality that enables detection of spatially correlated
magnetic noise at continuously tunable length scales down to 50 nanometers. These observations open the door toward practical applications of interaction-enhanced
quantum sensors for nanoscale biological imaging and material characterization.
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All authors Haoyang Gao, Piotr Put, Nathaniel T. Leitao, Nazl{\i} U. Köylüoğlu, Andrew Maccabe, Mathew Mammen, Siddharth Dandavate, Lillian B. Hughes Wyatt, Leigh S. Martin, Ania C. Bleszynski Jayich, Hongkun Park, Mikhail D. Lukin
Statistical Mechanics · Cross-listed from math-ph
Estimating the asymptotics of integer partitions in intermediate dimensions ($d = 3,4,5,6$)
Avinandan Mondal
It was recently shown by Yeliussizov \cite{Yeliussizov} that integer partitions in dimensions $d \geq 7$ asymptotically grow strictly faster than MacMahon numbers. As MacMahon numbers match with integer partitions in dimensions $d = 1,2$, the comparison of asymptotics of integer partitions with MacMahon numbers in intermediate dimensions ($d = 3,4,5,6$) is an open question. In this work, we perform Markov chain Monte Carlo (MCMC) simulations till $N=15000$ by using adaptive weight learning followed by conventional MCMC steps to numerically estimate the asymptotics of integer partitions in these intermediate dimensions. We numerically establish that in these intermediate dimensions, partitions asymptotically grow faster than MacMahon numbers. More specifically, assuming that the limits exist, we show: $\lim_{n\to\infty}n^{-3/4}\log p_3(n) = 1.8196 \pm 0.0019$, $\lim_{n\to\infty}n^{-4/5}\log p_4(n) = 1.7215 \pm 0.0045$, $\lim_{n\to\infty}n^{-5/6}\log p_5(n) = 1.6521 \pm 0.0059$, and $\lim_{n\to\infty}\log n^{-6/7}p_6(n) = 1.652 \pm 0.021$ for partitions in dimensions $d=3,4,5,$ and $6$ respectively. These numbers are all larger than MacMahon leading order asymptotic coefficients of $1.7898, 1.6614, 1.5737,$ and $1.509$ respectively. Additionally, we also find estimates for some of the sub-leading asymptotic terms in $\log p_d(n)$ in each of the dimensions.
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Strongly Correlated Electrons · Cross-listed from hep-th
Holographic zeros and poles from apparent singularities
Edwan Préau
We study general holographic fluctuation equations with apparent singularities, and the associated spectral functions. We consider the regime where an apparent singularity approaches the boundary, for which the near-boundary behavior of solutions can be determined via an inner/outer matching type of calculation. Depending on properties of the equation, we find that the merging of an apparent singularity with the boundary may generate either a zero or a pole for the corresponding spectral function. Our results also indicate that the recently introduced holographic product formula still applies in the presence of apparent singularities.
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Mesoscale and Nanoscale Physics
Tuning Andreev reflection and conductance in proximitized nanowires through the spin-orbit field direction
Leonardo Musca and Fabrizio Dolcini
We investigate the Andreev reflection (AR) and the nonlinear conductance in a normal-
superconductor junction realized with a proximitized
semiconductor nanowire exposed to a
magnetic field along its axis. We show that, while at zero energy the AR coefficient is determined by the topological phase of the superconducting side of the junction, at finite energy the AR is strongly affected by the directions of the Rashba
spin-orbit field characterizing the normal and the proximitized sides. The tunability of the AR and the nonlinear conductance as a function of the
spin-orbit misalignment angle is particularly pronounced when the proximitized side is in the topologically trivial phase. The
spin-orbit field direction is revealed to be an efficient knob to control the electron transport through the hybrid junction, realizing an electrically widely tunable device. The implementation in realistic setups is discussed.
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Statistical Mechanics
Microscopically exact transport equation for the quantum Calogero model
Vir B. Bulchandani and Fabian H. L. Essler
We derive an exact transport equation for the
quantum Calogero model, i.e. inverse-square interacting
bosons on a line, from microscopic first principles.
Strongly Correlated Electrons · Cross-listed from quant-ph
Computing with qLDPC Codes by Climbing the Chain Map Hierarchy
Rahul Sahay, David M. Long and Vedika Khemani
We develop a framework for logical computation with qLDPC codes that places logical Pauli, Clifford, and non-Clifford operations on the same footing. This brings the simple homological description of Pauli logicals to the patchwork landscape of logical Clifford and non-Clifford operations, providing a tool for the discovery of new logical gates. In particular, we define the chain map hierarchy: a family of chain complexes whose homology classes encode logical
unitary and code surgery operations at any level of the Clifford hierarchy, precisely analogous to the chain complex description of Pauli logicals. Consequently, intuition for Pauli logicals can be leveraged to discover new logical operations on qLDPC codes. For instance, the familiar ability to deform Pauli logicals with stabilizers—i.e. boundaries of the chain complex—becomes a way to search for constant-depth
unitary implementations of (non-)Clifford logical gates. Using this strategy, we discover constant-depth
unitary implementations of the full logical Clifford group on any number of blocks of the 2D toric code, including within a single block, and addressable logical CCZ gates on any triple of logical
qubits on any number of blocks of the 3D toric code. Beyond
manifold codes, we find addressable non-Clifford gates on codes with many encoded
qubits. The chain map hierarchy naturally encompasses and extends other constructions of logical gadgets, for instance providing a universal parameterization of cup products. As such, our work provides a unified, useful, and intuitive
language for computing with qLDPC codes.
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Superconductivity
Direct Validation of Superconductivity through Contact-Free Detection of Persistent Supercurrents Using Room-Temperature Quantum Magnetometry
Xinyi Zeng, Chengzhen Qin, Bowen Fan et al. (+9 more)
The accelerated emergence of new materials is driving the search for high temperature
superconductors, but rapid experimental validation remains a critical bottleneck, particularly for microscopic samples under high pressure. Here, we demonstrate one-step direct superconductivity validation through room-temperature, contact-free detection of remnant supercurrents. The technique utilizes a cryogen-free optically pumped atomic magnetometer to detect the temperature-dependent
magnetic field produced by supercurrents of a
superconductor. The superconducting transition is directly identified by the abrupt disappearance of
magnetic field from the remnant supercurrent above the transition temperature and the reversal of the supercurrent direction upon reversing the applied
magnetic field. Validated on YBCO microcrystals and REBCO tape, this technique detects pico-Tesla
magnetic fields from supercurrents induced by the ambient Earth's
magnetic field in a millimeter-sized REBCO square disk, as well as from sub-100 micrometer YBCO microcrystals compatible with high-pressure diamond anvil
cells. The use of a ferrite flux guide enables sensitive detection from centimeter-scale distances. Requiring no electrical contacts,
magnetic coils, or integrated
magnetic sensors, this non-invasive, room-temperature platform offers a scalable approach for high-throughput screening and validation of superconductivity.
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All authors Xinyi Zeng, Chengzhen Qin, Bowen Fan, Hammad Ahmed, Hui Fang, Stuart Long, Xiaonan Shan, Jiefu Chen, Shoujun Xu, Liangzi Deng, Ching W. Chu, Jiming Bao
Materials Science
IDMate: Finite-temperature error bounds for window-resolved self-consistent-field screening
Peng Kang, Da Wan, Shulin Bai et al. (+5 more)
We formulate a finite-temperature residual test in IDMate that bounds window-resolved electronic errors without a spectral-gap assumption. For a fixed
Hamiltonian and exact electron number, strong convexity of the
matrix Fermi
entropy bounds the density-
matrix distance and free-energy error within a selected window. The bound remains finite at spectral crossings and extends to weighted k points with a shared chemical potential. We also derive a distance correction for particle-number mismatch. Across $3{,}586$ stress trials in $70$ seeded perturbation ladders, $1{,}942$ proposals satisfy the screen with no observed violation of the $0.05$ window-distance criterion plus its numerical allowance. This criterion differs from the uncorrected exact-trace bound, which six of ten historical in-loop candidates exceed at the numerical-error scale. An accept-or-recover loop replaces ten reference-map evaluations while meeting terminal comparison criteria in three configurations that include oracle-subspace controls. Additional candidates built only from preceding-iteration orbitals yield two acceptances and one abstention. The silicon candidate has a window distance of $1.891\times10^{-13}$ but a normalized real-space density error of $3.754\%$. Analytic examples separate errors from complement occupations and interblock coupling. Window-level accuracy therefore does not imply full-state accuracy; the screen tests compressed proposal quality, independently of nonlinear SCF convergence or net acceleration.
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All authors Peng Kang, Da Wan, Shulin Bai, Zhen Li, Yu Liu, Lei Zheng, Li-Dong Zhao, Huibin Xu
Strongly Correlated Electrons
Valley polarization dependence of candidate even-denominator fractional quantum Hall states in monolayer graphene
Saswata Sahu, Amarendra Pr. Indra and Moumita Indra
We investigate even-denominator fractional
quantum Hall (EDFQH) states in monolayer
graphene, focusing on the experimentally observed filling fractions $\nu = 1/2$ and $\nu = 1/4$. Owing to the approximate SU(4)
symmetry arising from
spin and valley degrees of freedom,
graphene hosts a rich variety of multi-component fractional
quantum Hall states with different polarization configurations. Using the Chern-Simons composite
fermion framework for SU(4) systems, we construct candidate variational wave functions corresponding to distinct
spin, valley, and mixed polarization states. The ground-state energies of these states are evaluated numerically using the Coulomb interaction in spherical geometry. By comparing energies across different polarization sectors, we identify the energetically favored configurations at $\nu = 1/2$ and $\nu = 1/4$. Our variational energy comparison suggests that the energetically favored candidate states correspond to multi-component correlated
quantum Hall
liquids. Within the restricted family of trial states considered here, these states differ from a simple composite-
fermion Fermi-sea description. These findings provide insight into the role of valley polarization and SU(4)
symmetry in stabilizing even-denominator fractional
quantum Hall states in
graphene.
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Materials Science
Battery open-circuit voltage is not purely chemical
Andrea Giudici, Christoph Pohl, Alberto Salvadori et al. (+3 more)
Open-
circuit-voltage (OCV) curves are commonly treated as intrinsic chemical properties of electrode materials. However, this view is incomplete. In ion-insertion batteries, OCV also depends on mechanical state and microstructure. Using finite-element simulations and asymptotic analysis, we show that particle swelling and external loads promote particle–particle contact that generates compressive stresses, shifting the inserted-ion chemical potential. The OCV correction is nonlinear, follows Hertzian contact scaling, and depends on particle arrangement. Identical materials can therefore exhibit different OCV curves in different electrode microstructures. Furthermore, in full
cells, electrodes are mechanically coupled through the common stack stress. Thus,
cell OCV is a chemo-mechanical property of the entire battery architecture, not chemistry alone.
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All authors Andrea Giudici, Christoph Pohl, Alberto Salvadori, Colin Please, Manuel Landstorfer, Jon Chapman
Materials Science
Physics-Informed Neural Network Surrogate for Oxygen Vacancy Dynamics in epitaxial $\mathrm{SrTiO_3}$ on Si memristors via Dynamic Spectral Optimization
Rodion Podorozhny, Nikoleta Theodoropoulou and Jelena Tešić
Physics-informed neural networks (PINNs) offer a promising framework for modeling
semiconductor devices, yet standard architectures struggle with severe numerical stiffness and multiscale spatial discrepancies inherent to oxide
heterostructures. Here, we demonstrate a cascaded PINN architecture coupled with a custom second-order Chebyshev second kind
polynomial spectral optimizer (DSO V2 Hybrid) to model ion-electronic drift-
diffusion transport in Pt/SrTiO$_3$/Si memristive
heterostructures across a 20 nm STO film on a 380 $\mu$m Si substrate. By isolating potential, carrier density, and vacancy transport into four sequentially trained sub-neural-networks, our model circumvents condition numbers exceeding $10^{16}$ without operator splitting. The trained surrogate reproduces experimental conductive-AFM current-voltage hysteresis ($R^2 > 0.96$) while ensuring strict Poisson consistency across continuous space. Compared to conventional finite-element solvers (e.g., COMSOL), the PINN surrogate enables differentiable inverse parameter estimation and linear time inference.
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Statistical Mechanics
Constituent-Tagged Transfer Linking Cluster Dynamics to Static Scaling
Kenji Shinoda
Clusters that merge and split have no unique genealogy. Tracking the host size of a conserved constituent defines $q_*$ by $\langle(S_{t+\tau}/S_t)^{q_*}\rangle=1$, with $q_*\ne0$. Across coupled map networks, coagulation-fragmentation dynamics, and Vicsek systems, $q_*\simeq\alpha-2$ without fitting, where $c(s)\propto s^{-\alpha}$ on the same size window. Radius scans locate the known Vicsek interaction radius and recover an independently specified clustering scale in experimental active rods. Local scale covariance yields the relation, while a tent map counterexample shows when reducing the stationary balance at each parent size to one moment fails.
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Statistical Mechanics
Decoherence-controlled collective criticality in a two-dimensional quantum Stag Hunt
Rajdeep Tah
Physical decoherence can preserve the microscopic strategic neutrality (i.e. zero effective field and equal potential of the two homogeneous strategic orientations) of a
quantum game while changing the thermodynamic regime of the corresponding interacting population. We demonstrate this for an Eisert–Wilkens–Lewenstein (EWL) Stag Hunt embedded as independent nearest neighbor encounters on a square
lattice. For the restricted strategies $\mathsf{Q}=i\mathbb{Z}$ and $\mathsf{D}=i\mathbb{Y}$, noisy two-player payoff
matrices are determined for phase damping, depolarization, and amplitude damping and mapped exactly to channel dependent Ising parameters $\mathfrak{J}(\Gamma,p)$ and $\mathfrak{H}(\Gamma,p)$. Phase damping and depolarization show the clearest contrast: they share the same microscopic neutrality branch $\mathfrak{H}=0$, while only depolarization suppresses the interaction as $(1-p)^2$. At $\beta=1$, this produces an exact depolarization-driven square-
lattice critical point at $p_{*}\approx 0.233460\ldots$, whereas phase damping remains in the ordered coexistence regime along the same neutrality branch. Monte Carlo finite size scaling is consistent with two-dimensional Ising criticality and distinguishes field driven coexistence below $p_{*}$ from a smooth crossover above it. Amplitude damping additionally reveals a strong dependence on channel placement: the post-strategy neutrality branch reaches $\Gamma=0$ at $p=1/3$ and then disappears. Resource negativity further shows that microscopic two-
qubit entanglement and collective interaction strength are distinct quantities. The resulting extended
lattice remains an ordinary classical Ising system.
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Materials Science · Cross-listed from math.NA
Buckling Prediction for Nonlinear Elastic Beams with Soft Inclusions
Thien Tran-Duc, J.E. Bunder and A.J. Roberts
We develop an efficient and accurate multiscale computational framework for predicting the buckling and post-buckling behaviour of elastic beams containing periodically distributed soft inclusions. The framework extends our previous multiscale, patch, computational homogenisation for linear elasticity by incorporating nonlinearity, and thus enables accurate prediction of both the buckling onset and the subsequent post-buckling response. Microscale computations are performed only within a sparse set of small subdomains (patches), while the macroscale behaviour is recovered through a proven patch-coupling
algorithm. The scheme is assessed through quarter- and half-domain patch computations for beams with inclusion-to-
matrix Young's modulus ratios ranging from 0.001 to 1. The results show that reducing the inclusion stiffness lowers both the critical buckling strain and the critical buckling stress, indicating an increased susceptibility to instability, while producing a milder post-buckling response with smaller transverse deflections and stress drops.
Eigenvalue analysis of the Jacobian
matrix accurately predicts the onset of instability and the corresponding critical strain and stress. Bifurcation diagrams of the nonlinear buckled configurations under compressive loading, and a quantitative analysis of the effect of the interpolation order on the predicted buckling and post-buckling responses, are also presented. Comparisons with full-domain simulations demonstrate that the proposed framework accurately predicts both the buckling threshold and the post-buckling behaviour while substantially reducing the computational cost. The methodology is readily extendable to heterogeneous beams, plates, shells, and other engineering structures.
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Materials Science
Repairing PBE-Spurious Metallicity for HSE06-Level Screening of 2D Photocatalysts for Green Hydrogen Production
Ritam Chakraborty and Arpan Das
Semilocal PBE calculations can remove viable photocatalysts before screening by labeling narrow-gap
semiconductors as metals. We address this failure mode in the Computational 2D Materials Database (C2DB) by combining leakage-aware repair of PBE-spurious
metallicity with HSE06–PBE $\Delta$-learning. Stage~I classifies HSE06-unknown PBE metals using structural, chemical,
magnetic, and stability descriptors, while excluding HSE06/GW quantities and PBE electronic shortcuts. Stage~II learns $E_g^{HSE} - E_g^{PBE}$ for the corrected insulating population. The curated XGBoost regressor reconstructs HSE06 gaps with a mean absolute error of 0.108~eV ($R^2=0.989$), compared with 1.036~eV for raw PBE. The Stage~I classifier is used only for triage because the labeled true-metal class contains 29 materials; its best holdout performance gives 87.5% accuracy, 0.286 true-metal recall, and 0.643 balanced accuracy. The corrected pH~0 electronic screen yields 10 strict and 29 initial relaxed green-hydrogen photocatalyst candidates. Four strict and 18 relaxed candidates would fail the same 1.6–2.8~eV gap window at the PBE level. Targeted VASP HSE06 calculations for six ML-predicted compounds give material-level MAEs of 0.417, 0.182, and 0.110~eV for the C2DB-native, Magpie+structural, and curated models, respectively; \feat{1AgBr-1} shifts above the upper gap cutoff, leaving 28 retained relaxed candidates. The workflow shows that high-fidelity correction must be evaluated by candidate membership, not only by global regression error.
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Disordered Systems and Neural Networks · Cross-listed from physics.chem-ph
Low-Temperature Transport in Li-Ion Battery EC/EMC/FEC Electrolytes: Molecular Dynamics and Machine-Learning Modeling
İpek Yenda Ç{\i}nar, Oguzhan Orhan, M. Oluş Özbek et al. (+1 more)
Low-temperature operation imposes severe limitations on lithium-ion transport in battery electrolytes, yet the coupled effects of solvent composition and fluorinated additives in the cold-temperature regime remain insufficiently resolved. Here, we combine classical molecular dynamics (MD) and machine learning (ML) to investigate 1 M LiPF$_6$ electrolytes containing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and EC/EMC (3:7), with 0-10 mol% fluoroethylene carbonate (FEC), from 298 to 233 K. MD simulations quantify Li$^+$ self-
diffusion, Nernst-Einstein (NE) and Green-Kubo (GK) conductivities and local coordination, while Gaussian-process surrogates model conductivity across composition and temperature. Cooling produces a pronounced transport penalty, particularly in EMC-containing electrolytes, whose GK conductivity decreases by more than 98% at 233 K, compared with approximately 90% in EC-rich systems. Li$^+$ self-
diffusion activation energies are 0.49-0.54 eV for EMC-containing systems and 0.27-0.29 eV for EC-based systems. Within the EC family, 0-2 mol% FEC gives comparable cold-temperature transport, whereas 5-10 mol% FEC shows lower conductivity retention at the coldest simulated temperature. The analyzed coordination channels remain solvent dominated, while direct Li$^+$-FEC coordination is not quantified in the present RDF set.The Gaussian-process surrogates achieve composition-disjoint cross-validated RMSE values of 0.56 and 0.57 mS cm$^{-1}$ for NE and GK conductivity. Within the simulated
liquid-state trajectories, temperature and host-solvent composition dominate the bulk-transport response, with FEC acting as a secondary modifier.
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All authors İpek Yenda Ç{\i}nar, Oguzhan Orhan, M. Oluş Özbek, Şener Özönder
Mesoscale and Nanoscale Physics
Relaxation effects on Hartree-Fock ground states in twisted bilayer graphene at even integer fillings
Tianyu Kong, Alexander B. Watson, Lin Lin et al. (+2 more)
A standard approach for studying magic angle twisted bilayer
graphene (MATBG)'s correlated electronic phase diagram is to project the Coulomb interaction down to effective models only involving electrons in single-particle flat bands and some nearby remote bands. We provide a novel systematic derivation of a single-particle continuum model of MATBG's single-particle properties which incorporates structural relaxation while remaining in the Lagrangian frame. We project the Coulomb interactions down to electrons occupying the flat bands of this model and compute the Hartree-Fock many-body ground states at fillings $\nu = \pm 2$. We find that incorporating relaxation effects drives the model into a semi-metallic phase at $- 2$ because of particle-hole asymmetry in the relaxed model's single-particle dispersion and because the flat band wavefunctions become more concentrated leading to an enhanced Hartree potential. Our results corroborate recent ab initio density functional theory studies which also found semi-metallic phases at $-2$. We discuss potential explanations for why such phases have not been seen in experiments.
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All authors Tianyu Kong, Alexander B. Watson, Lin Lin, Mitchell Luskin, Kevin D. Stubbs
Materials Science
First Principle Analysis of the Magnetism and Electronic Structure of Fe2XSi (X=Ti, V)
Hanieh Kachooee, Cindy Kim, Jason Carbajal et al. (+2 more)
The electronic,
magnetic, and mechanical properties of Fe2XSi, where X is titanium (Ti) and vanadium (V), are investigated using computational methods. Volume optimization reveals that the ground state of Fe2TiSi is a nonmagnetic narrow-band gap
semiconductor, and that of Fe2VSi is a ferrimagnetic metal. The negative formation energies of both materials confirm the stability of their
crystal structures. Mechanical properties confirm the static stability of the
crystal structure and suggest that the titanium compound is ductile; however, the vanadium material is brittle. Density of states and band structure studies confirm the nonmagnetic semiconducting nature with an indirect band gap at {\Gamma} and X for the titanium material and the ferrimagnetic-metallic nature of the vanadium material. Electronic and
magnetic properties of the materials were investigated with applied tension (negative pressure) and compression (positive pressure) to the
crystal structure. The pressure study on Fe2TiSi shows a tunable band gap and a possible
semiconductor-metal transition, and Fe2VSi shows a tunable
magnetic moment and a possible low-
spin/high-
spin magnetic transition.
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All authors Hanieh Kachooee, Cindy Kim, Jason Carbajal, K. Hettiarachchilage, N. Haldolaarachchige
Materials Science
AlterSeeK-Path: Systematic construction of generalized band-structure paths for displaying altermagnetic spin splitting
Yujia Teng, Mesfin Eshete, Andrea Urru et al. (+4 more)
Altermagnetic materials exhibit
spin splitting in their electronic band structures while maintaining zero net magnetization. However, conventional high-
symmetry k-paths generally hide this splitting because they follow
symmetry lines that in most cases enforce
spin degeneracy. We present AlterSeeK-Path, an open-source Python tool that systematically constructs generalized band-structure paths for collinear altermagnets. The method selects the centroid of the conventional irreducible wedge used in routine band-structure calculations as the representative general k-point, maps it to a
spin-flip-related partner, and inserts paired segments through these points into the standard high-
symmetry path; these segments systematically sample the interior of the irreducible wedge. We demonstrate the construction for all 54 three-dimensional combinations of extended Bravais
lattice type and
spin Laue group across the six
crystal systems that support collinear altermagnetism, and for the 12 two-dimensional cases spanning the four compatible two-dimensional Bravais
lattices. Representative band structures are shown for the distinct
lattice/path cases. With AlterSeeK-Path, these band structures can be constructed with essentially the same effort as conventional band structures.
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All authors Yujia Teng, Mesfin Eshete, Andrea Urru, Daniel Seleznev, Se Young Park, Sebastian E. Reyes-Lillo, Karin M. Rabe
Mesoscale and Nanoscale Physics
Emergence of the magnetic octupole Rashba-Edelstein effect from spin-orbit entanglement
Hojun Lee and Seungyun Han
Magnetic multipoles have attracted growing interest as order parameters and dynamical degrees of freedom in unconventional magnets, yet it remains unclear how broadly they can emerge as active electronic degrees of freedom. Here, we show that
spin-orbit-entangled multiorbital states can host
magnetic octupole (MO) degrees of freedom. In Rashba systems, this gives rise to an MO Rashba texture accompanying the J-Rashba texture. Remarkably,
spin-orbital
entanglement can realize a pure-MO limit in which the
spin and orbital-angular-momentum textures vanish while the MO texture remains finite. An applied electric field converts this texture into a nonequilibrium MO polarization through an MO Rashba-Edelstein effect. Around the pure-MO regime, the MO Edelstein response dominates over the conventional
spin response, showing that multipolar responses need not be small corrections to dipolar
spin physics. Our results establish an interface-based route for electrically generating nonequilibrium multipolar
magnetic polarization in
spin-orbit-coupled systems.
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Materials Science
Systematic display of the spin splitting in band structures of representative altermagnetic crystals
Mesfin Eshete, Yujia Teng, Andrea Urru et al. (+4 more)
In this work we demonstrate a novel approach to exhibit the unique
spin splitting that is typical of collinear altermagnets. This approach is to plot band structures on Brillouin zone paths that sample general k-points to show a representative picture that corresponds to Brillouin zone averages. This is in contrast to conventional band structure plotting which plots band structures on the highest-
symmetry points and lines, and thus in many cases can fail to show any altermagnetic
spin splitting at all. Our investigation compares the new approach with the band structures of collinear altermagnets using conventional band structure plotting. We report the band structure and
symmetry analysis for MnTe, CrSb, SmFeO3, ScCrO3, LaMnO3, TlCrO3, HoFeO3, InCrO3 and DyFeO3. This result clearly demonstrates the advantage of this novel method for displaying the
spin splitting of collinear altermagnets.
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All authors Mesfin Eshete, Yujia Teng, Andrea Urru, Daniel Seleznev, Se Young Park, Sebastian E. Reyes-Lillo, Karin M. Rabe
Soft Condensed Matter
Relating solute interactions to interfacial properties
Varun Mandalaparthy, Benjamin M. Curlee and William G. Noid
Liquid interfaces are both ubiquitous and also critically important for many commercial products, modern technologies, biological processes, and environmental phenomena. The properties of these interfaces can depend quite sensitively upon the composition of the bulk
liquid phase. In this work, we develop a dilute solution theory (DST) for the influence of dilute cosolutes upon the interface between coexisting
liquid and vapor phases. We employ a grand canonical perturbation theory to rigorously relate the interfacial free energy to the concentration of the
liquid solution. We leverage a corresponding Gibbs ensemble to treat
liquid-vapor coexistence and to eliminate the contribution of the bulk phases from this free energy. We express the coefficients of the resulting expansion in terms of microscopic partition functions. By treating solute-solute interactions to lowest order, we distinguish between the intrinsic and effective interfacial preferences of solutes. While the former reflects only solute-solvent interactions, the latter depends upon the solution composition and reflects the influence of solute-solute interactions. We assess this DST with molecular dynamics simulations of binary and ternary mixtures of Lennard-Jones spheres. These simulations demonstrate that DST accurately models the interfacial properties of these systems up to relatively high concentrations. Moreover, the simulations illustrate the impact of attractive solute-solute interactions in converting weak intrinsic surfactants into weak effective depletants.
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Other Condensed Matter
Magnetoelectric Phase Transition and Axion Dynamics
Chen-Hui Xie, Runyu Lei, Jiayi Liu et al. (+4 more)
Magnetoelectric phase transitions have been experimentally studied, but no macroscopic theory has been proposed to explain their dynamical origin. In this work, we assume that the
axion quasiparticle with frequency undergoes a condensation like process. We show that these magnetoelectric phase transitions can be described within a Ginzbur Landau framework by introducing a coupled dynamic parameter, the
axion angle, which is proportional to the magnetoelectric coeffcient. We derive relations between the static
axion angle, the
axion frequency, and the phase transition temperature for different magnetoelectric materials, respectively, and compare these calculations with existing experimental results. We also connect the artificially designed Dzyaloshinskii Moriya interaction with the
axion condensate like process, so that the relation between the static
axion angle and the experimentally measured frequency shift can be obtained.
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All authors Chen-Hui Xie, Runyu Lei, Jiayi Liu, Yihuai Chen, Jinxing Zhang, Yu Gao, Sichun Sun
Materials Science · Cross-listed from physics.chem-ph
HiPoly: a hierarchical polymer-native AI framework for property prediction and generative design
Ge Sun, Gervasio Zaldivar, Yuan Tian et al. (+5 more)
Polymeric materials are central to modern technologies, with applications ranging from energy to health and transportation. Although AI has made significant advances in materials discovery, the hierarchical structure of
polymers across multiple length scales makes them inherently difficult to represent in a unified and physically meaningful way. Here we introduce HiPoly, a
polymer-native AI framework that processes complete
polymer descriptions through a three-level hierarchical graph architecture built on the G2RINS representation. HiPoly encodes
stochastic inter-monomer connectivity, composition, and molecular weight directly within its architecture, using physically motivated design principles that mirror the multi-scale nature of polymeric systems. The framework establishes an end-to-end AI-driven workflow from experimental formulation data to property prediction, generative molecular design, and physics-based validation through molecular simulations, all unified by a single
polymer representation. We demonstrate state-of-the-art prediction accuracy for thermophysical properties of multi-component
polymer systems, with ablation studies confirming that each hierarchical design choice contributes independently to model performance. As an example, the generative design pathway is applied here to the discovery of sustainable alternatives to persistent fluorinated
polymers, where it is possible to identify and independently validate PFAS-free candidates with target surface-energy properties. This work demonstrates how
polymer-native AI can accelerate discovery by linking representation, prediction, and design across complex
polymer chemistries.
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All authors Ge Sun, Gervasio Zaldivar, Yuan Tian, Gustavo Perez Lemus, Juhae Park, Daryna Safarian, Ming Han, Juan J. de Pablo
Materials Science
Understanding Graphene-Perovskite Interactions: From Flake Chemistry to Crystallisation and Solar Cell Performance
Oussama Er-Riyahi, Dorota Biernacka, Yating Guo et al. (+7 more)
Graphene-derivatives are widely employed materials to improve bulk and interface properties of metal-halide perovskite devices. Yet the implications of their flake chemistry and interactions with the perovskite precursors remain unclear. Here, we show that pristine
graphene flakes (GF) and more conventional
graphene oxide flakes (GOF) are not interchangeable. Density functional theory calculations reveal that GOF interacts more strongly with the perovskite
lattice but induces larger structural distortions, stronger interfacial polarisation, and localised gap states. In contrast, GF forms comparatively non-disruptive contacts, a response retained across a wide compositional range. Machine-learning atomistic simulations further show that GF contacts both Pb- and I-containing regions of solvated perovskite nanocrystals, with a strong solvent dependency. Solution spectroscopic characterization indicates that GF additives serve as scaffold for preorganised Pb/I-containing precursors, favouring film crystallisation. In this sense, GF enhances solar
cell performance across perovskite compositions, but particularly those facing a more challenging crystallisation. In mixed Sn-Pb perovskite solar
cells, GF raises the champion power-conversion efficiency from 21.5% to 23.7% with improved storage stability. These results establish pristine GF as a chemically defined additive and connect its atomic-scale interactions with precursor organisation, crystallisation, device performance, and stability.
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All authors Oussama Er-Riyahi, Dorota Biernacka, Yating Guo, Mikel Ballarena Tellechea, Silver-Hamill Turren-Cruz, Dario Bercioux, Meng Li, Agnieszka Lekawa-Raus, Jorge Pascual, Karolina Z. Milowska
Mesoscale and Nanoscale Physics
QArray+: A physics-informed GPU-accelerated simulator for quantum dot arrays
Pranav Vaidhyanathan, Barnaby van Straaten, Alice Petrillo et al. (+6 more)
Semiconductor quantum-dot arrays are a compelling platform for scalable
quantum technologies, yet their practical operation is hindered by the complexity of tuning large-scale devices. Existing automation tools rely on simplified physical models—such as constant-capacitance approximations and
equilibrium Hubbard models—which assume instantaneous relaxation to a steady state. These frameworks fail in experimentally critical regimes where measurement rates exceed tunneling dynamics, necessitating more sophisticated non-
equilibrium control strategies. To bridge this gap, we introduce QArray+, an extension of the QArray framework that incorporates gate-dependent tunnel coupling and a
quantum open-system description of dissipative processes. This approach enables the unified simulation of coherent interdot charge-state hybridization and the non-
equilibrium latching dynamics essential for training robust machine-learning models for automated device operation. Implemented in JAX with GPU acceleration, QArray+ scales across GPUs and multi-node systems. For example, a charge stability diagram for a 100X100 grid of gate voltages over 64 dots can be computed in $\sim0.17\,\mathrm{s}$ on multiple GPUs. Since interdot interactions are short-ranged and the corresponding tuning corrections are local, simulations at these scales capture the physics relevant to even larger devices. These capabilities support high-throughput
dataset generation for automated device tuning.
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All authors Pranav Vaidhyanathan, Barnaby van Straaten, Alice Petrillo, Rahul Marchand, Edwin De Nicolo, Menno Veldhorst, Brucek Khailany, Taylor L. Patti, Natalia Ares
Strongly Correlated Electrons · Cross-listed from quant-ph
Effective quasiparticle conserving Lindbladians in the thermodynamic limit
Lea Lenke and Kai Phillip Schmidt
Open
quantum many-body systems are commonly described by Lindblad master equations, yet the treatment of Lindbladian operators in the thermodynamic limit remains a major challenge. We develop a framework for constructing effective quasiparticle-conserving Lindbladian operators directly in the thermodynamic limit. Our approach extends continuous similarity transformations to non-Hermitian open
quantum systems and enables the systematic block diagonalization of Lindbladians with respect to the quasiparticle (qp) number. We formulate two complementary methods. The first, projective continuous similarity transformations (pcst++), generalizes perturbative continuous
unitary transformations to Lindblad operators so that a linked-cluster expansion allows us to obtain high-order series expansions of the infinite system. The second, deepCST, extends directly evaluated enhanced perturbative continuous
unitary transformations by combining the same qp-conserving generator with a perturbative truncation scheme that yields non-perturbative effective Lindbladian operators directly in thermodynamic limit. We apply pcst++ and deepCST to the dissipative transverse-field Ising chain with local dissipation. We focus on the low-Ising regime. We purify the Lindbladian by splitting each
spin into two sites. A
spin flip then corresponds to two qps. We derive and analyze the effective, qp-conserving Lindbladian in the sectors with zero to two qps. We show how the Ising interaction renormalizes the decay rates of elementary
spin-flip excitations and provides the microscopic mechanism for a competition between coherent interactions and dissipation. Our work establishes perturbative and non-perturbative continuous similarity transformations as a versatile tool for deriving effective qp pictures of open
quantum many-body systems in the thermodynamic limit.
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Mesoscale and Nanoscale Physics
Twist as a Mechanical Switch for Reconfigurable Stacking in h-BN
Gautham Vijayan, Zhaoheng Zhang, Kenji Watanabe et al. (+5 more)
Twistronics of layered materials has emerged as a highly active field due to its profound implications for
quantum electronics and materials engineering. However, the controllable manipulation of interlayer stacking remains a significant experimental challenge. Here, the homogeneous contact between hexagonal boron nitride layers is shown to be reproducibly switched between two distinct stable stacking configurations via an externally applied torque. Combining experiments and computational modelling, we identify the stacking order of these stable states as the commensurate AA and AB modes. These two states are associated with different rotational torque maxima, exhibiting an asymmetry ratio of 0.7, and distinct dynamics as a function of the twist angle. Moreover, the peak torque values scale linearly with contact area, highlighting the dominant role of edge elasticity in the twisting process. Given that the AA and AB stacking modes correspond to different out-of-plane electric polarization states, our findings offer a pathway for reconfigurable nano- and micro-electromechanical devices.
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All authors Gautham Vijayan, Zhaoheng Zhang, Kenji Watanabe, Takashi Taniguchi, Michael Urbakh, Oded Hod, Xiang Gao, Elad Koren