Materials Science
Multiple Topological States in LaAgAs2, a Failed Square-Net Semimetal
Yang Liu, Tongrui Li, Xixi Yuan et al. (+15 more)
The rational design of new materials emerges as an important direction to explore new topological materials, which is based on the understanding of the correlation between
crystal and electronic structures. In this paper, we perform a comprehensive study on the
crystal and electronic structures in LaAgAs2 through a combination of single-
crystal x-ray diffraction (XRD),
quantum oscillation, and angle-resolved photoemission spectroscopy (ARPES) experimental measurements, and density functional theory (DFT) calculations. Single-
crystal XRD measurements reveal that LaAgAs2 crystallizes into a HfCuSi2-derived structure with the square net distorted into cis-trans chains.
Quantum oscillation measurements reveal two frequencies with small effective masses and quasi-two-dimensional (2D) characters. ARPES measurements reveal an electronic structure strikingly different from the square-net-based semimetals, such as LaAgAs2. The
Fermi surface is quasi-two-dimensional (2D), with Dirac-like hole pockets at the zone center and a quasi-1D elliptical electron pocket at the zone boundary. Based on the DFT calculations, the measured electronic structure can be well understood regarding the cis-trans distortion, which transforms the two-dimensional square net-derived Dirac bands into quasi-1D trivial bands. Intriguingly, multiple topological states can be identified around the zone center, including a nontrivial Z2 topological surface state and a bulk Dirac state. Our study clarifies the impact of cis-trans distortion and identifies LaAgAs2 as a topological material with multiple topological states near the
Fermi level, providing a guideline for intentionally designing new topological materials.
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All authors Yang Liu, Tongrui Li, Xixi Yuan, Nour Maraytta, Alexei V. Fedorov, Asish K. Kundu, Turgut Yilmaz, Elio Vescovo, Xueliang Wu, Long Zhang, Mingquan He, Yisheng Chai, Xiaoyuan Zhou, Michael Merz, Zhe Sun, Huixia Fu, Tonica Valla, Aifeng Wang
Mesoscale and Nanoscale Physics
Kinetics-Driven Selective Stoichiometric Shift and Structural Asymmetry in $Bi_4Te_3$ Nanostructures for Hybrid Quantum Architectures
Abdur Rehman Jalil, Helen Valencia, Christoph Ringkamp et al. (+6 more)
Advances in hybrid
quantum architectures hinge on topological materials that can be synthesized with precise stoichiometric and structural control at the nanoscale. While $Bi_4Te_3$ is a promising candidate due to its dual topological phases, acting as both a strong topological
insulator and a topological crystalline
insulator, high-quality growth remains challenging due to a narrow stoichiometric window and high sensitivity to surface kinetics. Here, we establish a reproducible molecular beam epitaxy (MBE) process to produce stoichiometric, twin-free $Bi_4Te_3$ thin films with ultra-smooth surfaces and atomically sharp van der Waals stacks. By employing selective area epitaxy (SAE), we realize laterally confined $Bi_4Te_3$ nanostructures that exhibit a feature-dependent stoichiometric deviation. This phenomenon, which we term the selective stoichiometric shift, arises from the unequal lateral
diffusion of Bi and Te adatoms, revealing a direct coupling between adatom kinetics and nanoscale compositional stability. Atomic-resolution imaging further uncovers asymmetric van der Waals gaps within the stacking sequence, identifying an intrinsic structural asymmetry between the quintuple and
bilayer units. These findings provide fundamental insights into the crystallization of Bi_4Te_3$ and demonstrate a scalable route for integrating functional topological materials into next-generation superconducting hybrid
quantum circuits.
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All authors Abdur Rehman Jalil, Helen Valencia, Christoph Ringkamp, Abbas Espiari, Michael Schleenvoigt, Peter Schüffelgen, Gregor Mussler, Martina Luysberg, Detlev Grützmacher
Mesoscale and Nanoscale Physics
Robust valley-polarized excitonic Mott states and doublons enabled by stacking-controlled moiré geometry
Hao-Tien Chu, Shou-Chien Chiu, Meng-Che Yeh et al. (+12 more)
Atomically-thin moiré superlattices offer an optically accessible platform for interacting
bosons, where strong onsite repulsion $U_{xx}$ suppresses double occupancy and supports excitonic Mott states at unit filling. However, moiré confinement also enhances
phonon- and disorder-assisted relaxation, challenging the robustness of these correlated states under dissipation. Here we show that strengthening the intersite
exciton repulsion $V_{xx}$ between neighboring moiré
cells offers a distinct route to stabilizing unit-filling excitonic Mott states. In H-stacked WSe2/WS2, moiré confinement endows interlayer
excitons with an out-of-plane dipole and a pronounced in-plane quadrupolar charge distribution. Helicity-resolved transient photoluminescence, supported by first-principles-informed modelling, reveals that this quadrupolar geometry increases $V_{xx}$ at unit filling by at least a factor of two relative to the dipolar R-stacked
excitons. Despite a slight reduction in $U_{xx}$, the enhanced $V_{xx}$ yields a long-lived, valley-polarized excitonic Mott state at unit filling that persists for ~12 ns - more than twice as long as in R-stacks - and remains robust up to ~50 K. Beyond unit filling, the same geometry supports valley-polarized doublons with fourfold longer lifetimes than in R-stacks. These results establish moiré-
geometric control of intersite interactions as a route to stabilizing excitonic Mott states and doublons against dissipation in solids.
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All authors Hao-Tien Chu, Shou-Chien Chiu, Meng-Che Yeh, Yu-Wei Hsieh, Jia-Sian Su, Xiao-Wei Zhang, Jie-Yong Zeng, Po-Chun Huang, Si-Jie Chang, Kenji Watanabe, Takashi Taniguchi, Yunbo Ou, Seth Ariel Tongay, Ting Cao, Chaw-Keong Yong
Statistical Mechanics · Cross-listed from hep-lat
Order-separated tensor-network method for QCD in the strong-coupling expansion
Thomas Samberger, Jacques Bloch, Robert Lohmayer et al. (+1 more)
We introduce the order-separated Grassmann higher-order tensor renormalization group (OS-GHOTRG) method for QCD with staggered
quarks in the strong-coupling expansion. The method allows us to determine the expansion coefficients of the partition function, from which we can obtain the strong-coupling expansions of thermodynamical observables. We use the method in two dimensions to compute the free energy, the particle-number density, and the
chiral condensate as a function of the chemical potential up to third order in the inverse coupling $\beta$. Although near the phase transition the expansion is only a good approximation to the full theory at small $\beta$, we show that the range of applicability can be greatly extended by fits to judiciously chosen transition functions.
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All authors Thomas Samberger, Jacques Bloch, Robert Lohmayer, Tilo Wettig
Materials Science
Revealing Charge Transfer in Defect-Engineered 4Hb-TaS2
Siavash Karbasizadeh, Wooin Yang, Wonhee Ko et al. (+4 more)
We present a comprehensive first-principles investigation of defects in 4$H_b$-TaS$_2$. In this layered transition metal dichalcogenide, charge transfer between alternating Mott-insulating 1T and metallic 1H layers gives rise to exotic
quantum phases such as the Kondo effect and topological superconductivity. Motivated by recent defect manipulation in 4$H_b$-TaS$_2$ via STM, we address their microscopic nature and impact on interlayer charge transfer. To this end, we systematically analyze over 90 defects using large-scale density functional theory (DFT) calculations. Our analysis identifies 1H sulfur vacancies, Ta-on-S antisites, and Ta interstitials as the most likely origins of the commonly observed defects, with Ta-on-S antisites producing the strongest charge-transfer modulation. Our extensive
dataset, compiled from STM simulations, defect formation energies, work functions, and charge transfer, establishes a foundational resource for future theoretical and experimental studies on defect engineering in 4$H_b$-TaS$_2$.
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All authors Siavash Karbasizadeh, Wooin Yang, Wonhee Ko, Haidong Zhou, An-Ping Li, Tom Berlijn, Sai Mu
Materials Science
Fine-tuning universal machine learning potentials for transition state search in surface catalysis
Raffaele Cheula, Mie Andersen and John R. Kitchin
Determining transition states (TSs) of surface reactions is central to understanding and designing heterogeneous catalysts but remains computationally prohibitive with density functional theory (DFT). While machine learning potentials (MLPs) offer significant speedups, task-specific models have limited transferability across catalytic systems, and universal MLPs (uMLPs) lack the accuracy needed for reactive configurations. Here, we present a workflow based on active learning to iteratively fine-tune uMLPs for DFT-quality TS search. Using 250 TSs from the CO2 hydrogenation reaction network on metal and single-atom
alloy surfaces, we first
benchmark TS search
algorithms, identifying the Sella
algorithm as most robust, and propose a modification (Bond-Aware Sella) that substantially improves its success rate. We then explore sequential and batch active-learning strategies for fine-tuning and show that DFT-quality TS structures can be found using only 8 DFT single-point calculations on average per structure. This demonstrates the viability of fine-tuned uMLPs for high-throughput catalyst screening.
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Statistical Mechanics · Cross-listed from quant-ph
Nonequilibrium phases and quantum correlations in synthetic transport models
Uddhav Sen, Federico Carollo and Sascha Wald
Quantum devices featuring mid-
circuit measurement and reset capabilities, such as
quantum computers and dual-species Rydberg
quantum simulators, enable the realization of
quantum cellular automata. These systems evolve in discrete time following local updates implemented by
unitary gates, and allow for the realization of both closed and synthetic dissipative dynamics. Here, we focus on
quantum cellular automata that implement minimal models of classical and
quantum transport. To illustrate our ideas, we focus on a discrete-time totally asymmetric simple exclusion process and investigate how coherent dynamical contributions allow for the emergence of
quantum effects and correlations. We find that bipartite
entanglement dominates the transient
evolution, while stationary states can retain
quantum correlations beyond
entanglement. Our results suggest viable routes for realizing transport models on
quantum devices and characterizing collective
quantum correlations in strongly driven systems.
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Mesoscale and Nanoscale Physics
Tunable linear polarization of interface excitons at lateral heterojunctions
M. V. Durnev and D. S. Smirnov
We develop a theory of polarized photoluminescence of interface
excitons localized at lateral heterojunctions between transition metal dichalcogenide monolayers. We show that the circular selection rules governing interband optical transitions exactly at the band extrema are modified at finite wave vectors. The corresponding wave-vector-dependent corrections to the optical
matrix elements result in a net linear polarization of excitonic photoluminescence. We identify two microscopic mechanisms responsible for linear polarization$-$trigonal warping of the electron and hole dispersions and the energy dependence of the effective masses. Their interplay controls both the magnitude and the angle of the emitted light polarization, with distinct dependences on the crystallographic orientation of the interface. Using a microscopic variational approach, we demonstrate that the degree of linear polarization can reach values exceeding 10% in realistic
heterostructures. Furthermore, due to the large built-in dipole moment of interface
excitons, their optical response can be tuned by an external in-plane electric field, enabling control over the strength and direction of the polarization.
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Strongly Correlated Electrons
Intertwined spin and charge dynamics in one-dimensional supersymmetric t-J model
Yunjing Gao and Jianda Wu
Following the Bethe ansatz we determine the dynamical spectra of the one-dimensional supersymmetric t-J model. A series of fractionalized excitations are identified through two sets of Bethe numbers. Typical patterns in each set are found to yield wavefunctions containing elementary
spin and charge carriers, manifested as distinct boundaries of the collective excitations in the spectra of single electron Green functions. In
spin channels, gapless excitations fractionalized into two
spin and a pair of postive and negative charge carriers, extending to finite energy as multiple continua. These patterns connect to the half-filling limit where only fractionalized spinons survive. In particle density channel, apart from
spin-charge fractionalization, excitations involving only charge fluctuations are observed. Furthermore, nontrivial Bethe strings encoding bound state structure appear in channels of reducing or conserving magnetization, where
spin and charge constituents can also be identified. These string states contribute significantly even to the low-energy sector in the limit of vanishing magnetization.
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Strongly Correlated Electrons
RKKY-dipolar Interactions and 3D Spin Supersolid on Stacked Triangular Lattice
Ning Xi, Xitong Xu, Guoliang Wu et al. (+9 more)
Inspired by the recent discovery of metallic
spin supersolidity and its
giant magnetocaloric effect in the rare-earth
alloy EuCo$_2$Al$_9$ [Nature 651, 61 (2026)], we perform a combined study through electronic structure analysis, effective
spin model, and Monte Carlo simulations on a stacked triangular
lattice, and reveal a novel mechanism for the emergence of 3D
spin supersolid in a metallic antiferromagnet. From first-principles inputs, we derive a minimal
spin model on a stacked triangular
lattice (STL), which arises from the interplay between Ruderman-Kittel-Kasuya-Yosida (RKKY) and dipolar interactions and accurately reproduces the experimental thermodynamics. Based on the STL model, we identify a ground state that simultaneously breaks discrete
lattice translational
symmetry and continuous
spin-rotational
symmetry – the hallmark of a
spin supersolid. Furthermore, we present the field-temperature phase diagram of the 3D STL model and discuss the various
magnetic phases and associated phase transitions. Under zero field, the
spin supersolid Y order establishes in two steps: an upper transition at $T_{N1}$, where an emergent U(1)
symmetry appears and the system enters a fluctuating collinear regime, followed by a lower transition at $T_{N2}$ into the
spin supersolid Y phase. In contrast, the supersolid V phase undergoes a single phase transition at $T_N^V$. Our results not only provide a comprehensive theoretical understanding of the metallic
spin supersolid reported for EuCo$_2$Al$_9$ but also pave the way for further experimental investigations into its supersolid transitions and universality class.
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All authors Ning Xi, Xitong Xu, Guoliang Wu, Mingfang Shu, Hao Chen, Yuan Gao, Zhentao Wang, Gang Su, Jie Ma, Zhe Qu, Xi Chen, Wei Li
Strongly Correlated Electrons
Electrical Transport and Quantum Oscillations in the Metallic Spin Supersolid EuCo2Al9
Xitong Xu, Yonglai Liu, Ning Xi et al. (+16 more)
The discovery of
spin supersolid and its
giant magnetocaloric effect has opened a new arena in frustrated
quantum magnets and cutting-edge cryogenics. The intermetallic EuCo2Al9 (ECA), for the first time, extends this intriguing phase from Mott
insulators to a highly conductive metal [1]. In this work, we systematically study the electrical transport properties of ECA, where itinerant electrons serve as a sensitive probe for the
spin supersolid states. We observe anomalies both in the temperature-dependent resistivity and field-dependent magnetoresistance and
Hall signals, which are attributed to response of electrons to the Eu2+
spins and their fluctuations. Moreover, Shubnikov-de Haas
quantum oscillations at high
magnetic field reveal pronounced band splitting in the
spin polarized state. Our results reveal an intimate correspondence between electrical transport and
magnetic transitions in ECA, deepening the understanding of this metallic
spin supersolid.
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All authors Xitong Xu, Yonglai Liu, Ning Xi, Mingfang Shu, Haitian Zhao, Jiajun Xie, Guoliang Wu, Hao Chen, Miao He, Pengzhi Chen, Ze Wang, Zhentao Wang, Chuanying Xi, Mingliang Tian, Haifeng Du, Jie Ma, Xi Chen, Wei Li, Zhe Qu
Other Condensed Matter · Cross-listed from quant-ph
Introducing a Kondo-type interaction to the model of quantum walkers
Manami Yamagishi, Naomichi Hatano, Kohei Kawabata et al. (+4 more)
We introduce a model of discrete-time
quantum walkers interacting with a lozalized
magnetic impurity. Each
quantum walker interacts with an
impurity, through which multiple
quantum walkers indirectly interact with each other, as in the Kondo model. We first identify a
quantum walker as a massless Dirac particle propagating in continuous space via a series of Dirac's delta potentials. Based on the identification, we add a
spin-$1/2$ degree of freedom to Dirac's potential at the origin. We derive all scattering
matrices for massless Dirac particles arising from the
impurity. First, for a simple set of parameter values, we analytically obtain the
eigenvalues and eigenvectors of the bound states, in which a
quantum walker is bound to the
magnetic impurity. Second, we study two
quantum walkers indirectly interacting with each other via the
magnetic impurity. We numerically simulate the collision dynamics in one dimension when the
spin-
spin interaction at the origin is of the XX type and the SU(2) Heisenberg type. In the case of the XX interaction, we calculate the
entanglement negativity to quantify how much the two
quantum walkers are entangled with each other, and find that the negativity increases drastically upon the collision of the two walkers. In the case of the SU(2) Heisenberg interaction, we simulate the dynamics starting from the initial state in which one fermionic walker is in a bound eigenstate around the origin and the other fermionic walker is a delta function colliding with the first walker. We find that a bound eigenstate closest to the singlet state of the first walker and the
magnetic impurity is least perturbed by the collision of the second walker. We speculate that this finding may be related to Kondo screening-like behavior at the lowest level of the real-space renormalization-group procedure.
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All authors Manami Yamagishi, Naomichi Hatano, Kohei Kawabata, Chusei Kiumi, Akinori Nishino, Franco Nori, Hideaki Obuse
Soft Condensed Matter
Models of 3D confluent tissue as under-constrained glasses
Chengling Li, Matthias Merkel and Daniel M. Sussman
The dynamics of glassy materials slows down upon cooling, typically showing either Arrhenius or super-Arrhenius behavior. However, it was recently shown that 2D
cell-based models for biological tissues can be continuously tuned between Arrhenius and sub-Arrhenius dynamics. In previous work, using the 2D Voronoi model, we proposed that such atypical dynamical behavior could be a generic feature of the broad class of mechanically under-constrained materials. Our earlier study had left two important points open: (1) many 2D systems are affected by long-wavelength fluctuations and the 2D melting scenario, and (2) the 2D Voronoi model sits exactly at the isostatic point, making it a marginal case rather than a strictly under-constrained one. Both points complicate the interpretation of our 2D Voronoi model results and their generalization to other systems; to remedy this, here we use large-scale simulations to study the glassy behavior of the 3D extension of the Voronoi model. We first show that the structural relaxation time $\tau_\alpha$ of the 3D Voronoi model can be tuned between sub-Arrhenius and Arrhenius behavior, like the 2D Voronoi model. We then establish that the four-point susceptibility, the structure factor, and the model's mechanical properties all display trends consistent with the 2D Voronoi model. These results provide strong evidence that sub-Arrhenius glassy dynamics are a generic feature of under-constrained materials across dimensions. Our work thus broadens the class of disordered materials known to have highly unusual glassy phenomenology.
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Materials Science
Substrate-dependent pore formation in molybdenum disulfide monolayers under ion irradiation
Y. Liebsch, U. Javed, L. Skopinski et al. (+11 more)
Ion irradiation is a versatile tool for nanostructuring surfaces, yet the roles of energy deposition and dissipation at the surface and in ultrathin materials remain poorly understood. In this study, we investigate nanopore formation in monolayer MoS$_2$ on different substrates under irradiation of highly charged ions (HCIs) and swift heavy ions (SHIs): two types of ions that, despite having vastly different kinetic energies, interact primarily with the electronic system of the target. Using scanning transmission electron microscopy, we quantify pore radii and pore formation efficiencies for suspended MoS$_2$, MoS$_2$ on SiO$_2$,
bilayer MoS$_2$ and MoS$_2$ on gold. Both pore size and pore formation efficiency exhibit a pronounced dependence on the type of substrate. Pores are largest and most frequent in MoS$_2$ on SiO$_2$, while the gold substrate massively quenches pore formation. The results indicate that the observed pore dimensions under both HCI and SHI irradiation are consistent with a central role of substrate and interface-dependent electronic dissipation pathways.
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All authors Y. Liebsch, U. Javed, L. Skopinski, L. Daniel, F. Appel, R. Rahali, C. Grygiel, H. Lebius, C. Frank, L. Breuer, L. Kirsch, F. Koch, J. Kotakoski, M. Schleberger
Mesoscale and Nanoscale Physics
Fragile topology for six-fold rotation symmetry indicated by the concentric Wilson loop spectrum
Xinyang Li, Lumen Eek, Jasper van Wezel et al. (+1 more)
We investigate topological phase transitions for the Haldane and Kane-Mele model in a
lattice with $p6$
symmetry, which consists of triangles and hexagons arranged in a two-dimensional geometry. For the Haldane model, which breaks time-reversal
symmetry, we calculate the Chern number using a multi-band non-Abelian Wilson loop formalism. By varying the hopping parameters in the triangles and hexagons independently, a large variety of topological phases emerge. In the presence of a next-next-nearest neighbor hopping, the phase diagram becomes even richer, with regions exhibiting high Chern numbers. Then, we consider the Kane-Mele model, for which time-reversal
symmetry is preserved, and calculate the number of $\pi$-crossings in the Concentric Wilson Loop Spectrum (CWLS). This method is appropriate to determine the topological invariant for systems hosting time-reversal and rotational
symmetry, but lacking all other
symmetries. According to a classification based on $K$-theory, the CWLS invariant reveals topological properties even when more conventional invariants fail to detect them. The formalism was previously successfully applied to systems with 3- and 4-fold
symmetry. Here, we surprisingly find that for the 6-fold-
symmetry model investigated, the
topology identified by this invariant is fragile, therefore questioning the claim that this should be the strong invariant missing in a complete classification of topological
insulators.
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All authors Xinyang Li, Lumen Eek, Jasper van Wezel, Cristiane Morais Smith
Strongly Correlated Electrons · Cross-listed from nucl-th
Qcombo: A Python Package for Automated Commutator Calculations of Quantum Many-Body Operators
L. H. Chen, Y. Li, H. Hergert et al. (+1 more)
qcombo is a Python package for the symbolic evaluation of commutators between general
quantum many-body operators expressed in normal-ordered form using the generalized Wick
theorem. The package provides an automated and systematic framework for generating the corresponding algebraic expressions, significantly reducing the risk of human error in lengthy and complex analytical derivations. It is designed to assist the development and implementation of modern many-body methods in
nuclear physics,
quantum chemistry, and related fields. The functionality and workflow of the package are demonstrated through an application to the in-medium similarity renormalization group (IMSRG) method, which has been widely used for
nuclear ab initio calculations. As a representative example, qcombo is employed to automatically generate the complete set of multi-reference IMSRG flow equations with operators truncated at the normal-ordered three-body level.
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All authors L. H. Chen, Y. Li, H. Hergert, J. M. Yao
Materials Science
Plasmonic Mediated Atomically Engineered 2D Aluminium Quasicrystals for Dopamine Biosensing
Saswata Goswami, Guilherme S. L. Fabris, Diganta Mondal et al. (+7 more)
Dopamine levels are linked to neurological illnesses like Parkinson's and Alzheimer's. Thus, reliable and sensitive detection of dopamine is crucial for early diagnosis and surveillance of neurodegenerative diseases. Non-noble-metal-based nanomaterials are ideal for light-mediated sensing of organic molecules. Among these, 2D quasicrystal structures consisting of five elements, namely Al70Co10Fe5Ni10Cu5, provide active sites due to their high surface-to-volume ratio, making them excellent for organic chemical sensing. Here, we propose a simple, label-free, spatial self-phase-modulation (SSPM)-based sensing method in
liquid form. SSPM-based time
evolution of the diffraction pattern for varied mixing levels of a 1100 ppb dopamine solution shows a shift in the active 2D Al QC solution. The 1100 ppb solution shows a distinct value, indicating a change in the nonlinear refractive index. Time-
evolution analysis is used to calculate sensitivities to changes in the nonlinear refractive index and time constant. The SPR-activated 2D Al QC nanostructure is used to demonstrate dopamine sensing and to perform qualitative and quantitative evaluations. The SSPM-based sensing has been further compared with other optical-based sensing methods such as Raman spectroscopy, UV-Vis spectroscopy, and FTIR spectroscopy. The experimental observations are also explained using DFT-based simulations. The current SSPM method can be used for rapid, large-scale medical diagnostics.
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All authors Saswata Goswami, Guilherme S. L. Fabris, Diganta Mondal, Raphael B. de Oliveira, Anyesha Chakraborty, Thakur Prasad Yadav, Nilay Krishna Mukhopadhyay, Samit K. Ray, Douglas S. Galvão, Chandra Sekhar Tiwary
Superconductivity
Superconducting properties of lifted-off Niobium nanowires
A. Kotsovolou, F. Soofivand, P. Singha et al. (+7 more)
Hybrid
superconductor/
semiconductor devices play a crucial role in advancing
quantum science and technology by merging the properties of
superconductors and
semiconductors. To operate these devices at high temperature, Niobium could substitute the widespread aluminum as superconducting element. Niobium devices show the best superconducting properties when shaped by etching, but this technique is often incompatible with
semiconductors and two-dimensional materials. Our work investigates the influence of oxygen
diffusion on the superconducting transition of Nb nanowires fabricated by lift-off technique. To this scope, we fabricate and measure Nb devices of different width (W) and thickness (t). By using the Berezinskii-Kosterlitz-Thouless (BKT) model for charge transport, we demonstrate that our nanowires behave as two-dimensional
superconductors regardless of W and t. While the normal-state transition temperature (TN) remains constant with decreasing W, the temperature of the fully superconducting state (TS) decreases. Thus, the superconducting transition width ({\delta}TC) increases as W shrinks, due to oxygen
diffusion from the lithography resist occurring during deposition. These insights provide essential knowledge for optimizing Nb-based hybrid
quantum devices, paving the way for operating temperatures above 2 K and contributing to the development of next-generation
quantum technologies.
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All authors A. Kotsovolou, F. Soofivand, P. Singha, D. Cecca, R. Balice, F. Carillo, C. Puglia, G. De Simoni, F. Bianco, F. Paolucci
Mesoscale and Nanoscale Physics · Cross-listed from hep-th
soliton_solver: A GPU-based finite-difference PDE solver for topological solitons in two-dimensional non-linear field theories
Paul Leask
This paper introduces
soliton_solver, an open-source GPU-accelerated software package for the simulation and real-time visualization of topological
solitons in two-dimensional non-linear field theories. The software is structured around a theory-agnostic numerical core implemented using Numba CUDA kernels, while individual physical models are introduced through modular theory components. This separation enables a single computational framework to be applied across a broad class of systems, from nanoscale
magnetic spin textures in condensed matter physics to
cosmic strings spanning
galaxies in high energy physics. The numerical backend provides finite-difference discretization, energy minimization, and GPU-resident evaluation of observables. A CUDA–PyOpenGL rendering pipeline allows direct visualization of evolving field configurations without staging full arrays through host
memory. The package is distributed in Python via PyPI and supports both reproducible batch simulations and interactive exploration of metastable configurations,
soliton interactions, and model-dependent initial states. We describe the software architecture, numerical workflow, and extensibility model, and we present representative example applications. We also outline how additional theories can be incorporated with minimal modification of the shared numerical infrastructure.
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Materials Science · Cross-listed from physics.comp-ph
Aluminum solidification and nanopolycrystal deformation via a Graph Neural Network Potential and Million-Atom Simulations
Ian Störmer and Julija Zavadlav
Solidification governs the microstructure and, therefore, the mechanical response of metal components, yet the atomistic details of nucleation and defect formation are often difficult to determine experimentally. Molecular dynamics can bridge this gap, but only if the interatomic model is both accurate and computationally efficient. Here, we develop a Machine Learning Potential (MLP) for aluminum and demonstrate its near ab initio fidelity when trained with the sequential-refinement workflow that fine-tunes the model on low-energy structures. The favorable scaling of the model enables nanosecond simulations involving millions of atoms, thereby overcoming finite-size effects in simulations of polycrystalline solidification and subsequent mechanical testing. Comparison with classical potentials and recent MLP models, including a general-purpose model, shows that inaccuracies in stacking-fault energetics and
diffusion can lead to qualitatively incorrect solidified grain structures and post-solidification mechanical behavior. Since our framework is based on an equivariant graph neural network, it allows for straightforward extensions to multi-component systems, providing valuable guidance for the future design and fine-tuning of both specialized and universal MLPs in computational mechanics simulations.
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Strongly Correlated Electrons
Breakdown of the periodic potential ansatz in correlated electron systems
Wouter Montfrooij
Our electronic structure theory for crystalline solids is commonly built on the periodic potential assumption $V(\mathbf r)=V(\mathbf r+\mathbf R)$ for every
lattice translation $\mathbf R$, enabling Bloch eigenstates,
crystal momentum as a good
quantum number, and the standard quasiparticle-based description of the behavior of metals. Because the zero-point motion of the ions, however, in correlated electron systems the electronic environment experienced by an itinerant electron is neither static nor self-averaging at the single-particle level, even in perfectly stoichiometric
crystals, leading to a distribution of local Kondo scales that spans two orders of magnitude in temperature. We discuss, through a comparison between uniform scenarios and one that breaks with perfect
lattice translational
symmetry, how incorporating this distribution yields a unified description for all heavy-
fermion systems at the
quantum critical point.
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Statistical Mechanics · Cross-listed from quant-ph
Strong-to-Weak Spontaneous Symmetry Breaking in a $(2+1)$D Transverse-Field Ising Model under Decoherence
Yi-Ming Ding, Yuxuan Guo, Zhen Bi et al. (+1 more)
Decoherence in many-body
quantum systems can give rise to intrinsically mixed-state phases and phase transitions beyond the pure-state paradigm. Here we study the $(2+1)$D transverse-field Ising model subject to a strongly $\mathbb{Z}_2$-symmetric decoherence channel, with a focus on strong-to-weak spontaneous
symmetry breaking (SWSSB). This problem is challenging because the relevant transitions occur in the strong-decoherence regime, beyond the reach of perturbative expansions around the pure-state limit, while conventional
quantum Monte Carlo (QMC) methods are hampered by the need to access nonlinear observables and by the sign problem. We overcome these difficulties by developing a QMC
algorithm that efficiently evaluates nonlinear Rényi-2 correlators in higher dimensions, complemented by an effective field-theoretic approach. We show that the decohered state realizes a rich mixed-state phase diagram governed by an effective 2D Ashkin-Teller theory. This theory enables analytical predictions for the mixed-state phases and the universality classes of the phase boundaries, all of which are confirmed by large-scale QMC simulations.
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All authors Yi-Ming Ding, Yuxuan Guo, Zhen Bi, Zheng Yan
Materials Science
Automated Spin-Assisted Layer-by-Layer Epitaxy Produces Highly Oriented Mixed-Linker MOF Thin Films
Eleonora Afanasenko, Benedetta Marmiroli, Behnaz Abbasgholi-NA et al. (+11 more)
Control over crystallographic orientation in metal-organic framework (MOF) thin films is crucial for exploiting their anisotropic properties in sensing, catalysis, and separation. Achieving reproducible, highly oriented films remains challenging, especially for mixed-linker, pillared-layered frameworks. Here we present an automated,
spin-assisted layer-by-layer
liquid-phase epitaxy (LbL-LPE) strategy that enables rapid, ambient-condition fabrication of highly oriented, mixed-linker MOF thin films, demonstrated for Zn2BDC2DABCO (BDC = terephthalate, DABCO = 1,4-diazabicyclo[2.2.2]octane). Correlative process monitoring by grazing-incidence wide-angle X-ray scattering (GIWAXS), grazing-angle infrared (GI-IR) and UV-Vis spectroscopy, contact-angle measurements, scanning electron microscopy (SEM), and time-of-flight secondary ion mass spectrometry (ToF-SIMS) ensure formation of uniform films with exceptional out-of-plane (001) orientation (degree of orientation >85%, Hermans parameter ~0.95) and excellent reproducibility. This strategy enables highly reproducible, high-throughput fabrication of orientation-controlled MOF thin films, providing a generalizable alternative to conventional LbL approaches. By enabling reproducible and entirely automated fabrication of highly anisotropic architectures, this work establishes a platform for integrating oriented MOFs into next-generation optoelectronic, sensing, and membrane devices where directional transport and ordered pore
alignment are essential.
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All authors Eleonora Afanasenko, Benedetta Marmiroli, Behnaz Abbasgholi-NA, Barbara Sartori, Giovanni Birarda, Chiaramaria Stani, Matjaž Finšgar, Peter E. Hartmann, Mark Bieber, Emma Walitsch, Rolf Breinbauer, Simone Dal Zilio, Sumea Klokic, Heinz Amenitsch
Strongly Correlated Electrons
Universal Quantum Suppression in Frustrated Ising Magnets across the Quasi-1D to 2D Crossover via Quantum Annealing
Kumar Ghosh
Quantum magnets in the $M\mathrm{Nb_2O_6}$ and BaCo$_2$V$_2$O$_8$ families realise frustrated transverse-field Ising models whose competing
ferromagnetic and
antiferromagnetic couplings generate a sign problem provably intractable for
quantum Monte Carlo at any system size, leaving their
quantum phase boundaries numerically Inaccessible. Using a D-Wave Advantage2
quantum annealer at $L\leq27$ (729
spins), we obtain the large-$L$ critical points for this model family, measuring
quantum-driven transitions at ${g_c^{\mathrm{QPU}}}\in\{0.286,\,0.210,\,0.156,\,0.093\}$ for $\alpha\in\{1.0,\,0.7,\,0.5,\,0.3\}$, where the analytically exact classical threshold is ${g_c^{\mathrm{class}}}(\alpha)=2\alpha/3$. The suppression ratio $r(\alpha)$ exhibits a sharp two-regime structure: the three quasi-1D geometries ($\alpha\leq0.7$) are mutually consistent with a universal plateau $\bar{r}=0.450$ ($\chi^2/\mathrm{dof}=1.10$, $p=0.33$), demonstrating that
quantum fluctuations destroy approximately $55\%$ of the classical FM stability window independently of coupling anisotropy, while $r$ steps down to the 2D limit above the empirical crossover scale $\alpha^*\approx0.7$. Inner Binder cumulant pairs, which converge fastest to the thermodynamic limit, resolve $r(1.0)\approx0.412$ and a step $\Delta r=0.038\pm0.015$ from the quasi-1D plateau. A four-point linear fit $r(\alpha)=0.494-0.063\,\alpha$ summarises both regimes; its $\alpha\to0$ intercept recovers the exact 1D result of Pfeuty within 1.7 standard deviations, and its slope is a lower bound on the true crossover amplitude concentrated in $\alpha\in[\alpha^*,1]$. Two sequential blind predictions, confirmed at $0.2\sigma$ and $0.7\sigma$ before each measurement, validate the crossover law. All four geometries show a direct ferromagnet-to-paramagnet transition, complete
quantum ergodicity ($f_{\rm uniq}=1.000$), and null valence-bond solid order.
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Other Condensed Matter
Classification of intrinsically mixed $1+1$D non-invertible Rep$(G) \times G$ SPT phases
Youxuan Wang
We classify $1+1$d bosonic SPT phases with non-invertible
symmetry $\mathrm{Rep}(G)\times G$, equivalently the fusion-category
symmetry $\mathcal{H}=\mathrm{Rep}(G)\times\mathrm{Vec}_G$. Focusing on intrinsically mixed phases (trivial under either factor alone), we use the correspondence between $\mathcal{H}$-SPTs, $\mathcal{H}$-modules over $\mathrm{Vec}$, and fiber functors $\mathcal{H}\to\mathrm{Vec}$ to obtain a complete classification: such phases are parametrized by $\phi\in\operatorname{End}(G)$. For each $\phi$ we identify the associated condensable (Lagrangian)
algebra $\mathcal{A}_\phi$ in the bulk $\mathcal{Z}(\mathcal{H})\simeq\mathcal{D}_G^2$. We further provide an explicit
lattice realization by modifying Kitaev's
quantum double model with a domain wall $\mathcal{B}_\phi$ and smooth/rough boundaries, and then contracting to a 1D chain, yielding a (possibly twisted) group-based cluster state whose ribbon-generated
symmetry operators encode the same $\phi$.
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Materials Science
Lattice-Expansion-Driven Stabilization of Helical Magnetic Order in Ru-Doped MnP
Xin-Wei Wu, Deng-lu Hou, Li Ma et al. (+3 more)
The practical utilization of MnP in
chiral spintronic devices is fundamentally constrained by its low helical ordering temperature ($T_{\rm S}$). Here, we demonstrate that Ru substitution in Mn$_{1-x}$Ru$_x$P single
crystals drives a highly anisotropic
lattice expansion, where the $b$-axis elongation is one-quarter that of the $a$- and $c$-axes ($\sim$ 0.04 Å). This structural distortion profoundly stabilizes the helical ground state, elevating $T_{\rm S}$ from 51~K to 215~K and the critical field along the [010] direction at 5~K from 2.3 to 30.0~kOe, while suppressing the Curie temperature ($T_{\rm C}$) from 291~K to 215~K. Synthesizing these results with reported data on Mo- and W-doped analogues reveals that $T_{\rm S}$ and $T_{\rm C}$ are governed primarily by the $b$-axis parameter, exhibiting universal linear scaling relationships ($dT_{\rm S}/db = 1.59 \times 10^4\ \text{K\AA}^{-1}$, $dT_{\rm C}/db = 0.69 \times 10^4\ \text{K\AA}^{-1}$) far greater than those associated with the $a$- or $c$-axes. First-principles calculations reveal that the
lattice expansion selectively attenuates
ferromagnetic coupling while preserving
antiferromagnetic interactions between nearest-neighbor Mn atoms, thereby enhancing
magnetic frustration and stabilizing helimagnetism. These findings establish chemical pressure via directed $b$-axis engineering as a robust, generalizable paradigm for stabilizing helimagnetism in MnP.
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All authors Xin-Wei Wu, Deng-lu Hou, Li Ma, Cong-mian Zhen, De-wei Zhao, Guoke Li
Statistical Mechanics
Run, Tumble and Paint
Emir Sezik, Callum Britton, Alex Touma et al. (+1 more)
The visit probability, quantifying whether a particle has reached a given point for the first time by a specified time, provides access to various extreme value statistics and serves as a fundamental tool for characterising active matter models. However, previous studies have largely neglected how the visit probability depends on the internal degree of freedom driving the active particle. To address this, we calculate the "state-dependent” visit probability for a Run-and-Tumble particle, that is the probability that the particle first passes through $x$ before time $t$, keeping track of its internal state during first passage. This process may be thought of as the particle "painting” the positions it passes through for the time in the colour of its self-propulsion state. We perform this calculation in one dimension using Doi-Peliti field theory, by extending the tracer mechanism from previous works to incorporate such "polar deposition” and demonstrate that state-dependent visit probabilities can be elegantly captured within this field-theoretic framework. We further derive the total volume covered by a right- (or left-) moving Run-and-Tumble particle and compare our results with known expressions for Brownian motion.
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All authors Emir Sezik, Callum Britton, Alex Touma, Gunnar Pruessner
Materials Science
Exploring the Structure and Chemistry of 1D and 2D Lepidocrocite TiO2 at Atomic Resolution
Eric Nestor Tseng, Jonas Björk, Risha Achaiah Iythichanda et al. (+6 more)
Low dimensional materials are critical for enabling next generation applications that are central to addressing critical global challenges. Titanium dioxide nanostructures stand out due to their structural versatility and relevance to catalysis, energy conversion, and environmental remediation. Here, we employ a combination of advanced electron microscopy, spectroscopy, and first principles theoretical calculations to investigate the structural and chemical properties of one and two dimensional lepidocrocite type titania. Special emphasis is placed on the one dimensional material, which exhibits anisotropic growth, extending exclusively along a single crystallographic direction. Our analysis suggests that this unusual growth behavior can be attributed to light element
impurities, such as carbon, that are incorporated during the bottom up synthesis. The results extend the understanding for these unexplored low dimensional titania materials and offer fundamental insights into their structure and chemistry.
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All authors Eric Nestor Tseng, Jonas Björk, Risha Achaiah Iythichanda, Wei Zheng, Hatim Alnoor, Wei Hsiang Huang, Ming-Hsien Lin, Johanna Rosén, Per O.Å. Persson
Materials Science
Mn substitution induced a ferrimagnetic to ferromagnetic transition in trigonal $\text{Cr}_5\text{Te}_8$
Ze-Xin Liu, Yu Liu, Sen-Miao Zhao et al. (+4 more)
Tailoring the
magnetic properties of chromium tellurides via heterointercalation with extrinsic transition metals remains largely unexplored. Here, we report a comprehensive investigation of trigonal Cr$_5$Te$_8$ and Cr$_4$MnTe$_8$ single
crystals, in which Mn substitution elevates the
magnetic ordering temperature from 226 to 249 K and enhances the saturation
magnetic moment per
magnetic ion ($m_{\text{S}}$) from 2.00 to 2.66 $\mu_{\text{B}}$ at 5 K. Remarkably, the observed $m_{\text{S}}$ enhancement significantly exceeds the contribution of Mn ion moments alone, indicating the relief of intrinsic
spin compensation within the parent
lattice. First-principles calculations definitively establish that pristine $\text{Cr}_5\text{Te}_8$ exhibits ferrimagnetic ordering with a computed $m_\text{S}$ of 1.98~$\mu_\text{B}$, and further reveal that preferential occupation of the van der Waals gaps by Mn ions induces a ferrimagnetic-to-
ferromagnetic transition, yielding a predicted $m_\text{S}$ of 2.94~$\mu_\text{B}$. These findings not only resolve the
magnetic ground state of trigonal Cr$_5$Te$_8$ but also identify heterointercalation as a robust strategy for engineering the
spin textures of chromium tellurides.
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All authors Ze-Xin Liu, Yu Liu, Sen-Miao Zhao, De-Wei Zhao, Li Ma, Deng-Lu Hou, Guo-Ke Li
Mesoscale and Nanoscale Physics
A material-agnostic platform to probe spin-phonon interactions using high-overtone bulk acoustic wave resonators
Q. Greffe, A. Hugot, S. Zhang et al. (+6 more)
Spin-
phonon interactions have a dual role in emerging
spin-based
quantum technologies. While they can be a limitation to device performance through decoherence, they also serve as a critical resource for coherent
spin control, detection, and the realization of
spin-based
quantum networks. However, their direct characterization remains a challenge and is usually material-dependent. Here, we introduce a technique to probe
spin-
phonon coupling at millikelvin temperatures and gigahertz frequencies, using high-overtone bulk acoustic wave resonators (HBARs) integrated with arbitrary
crystals via visco-elastic transfer of thin-film lithium niobate transducers. By tuning the Larmor frequency of dilute
spin ensembles into resonance with HBAR modes, we extract the anisotropy and strength of
spin-
phonon interactions from acoustic dispersion and dissipation measurements. We demonstrate this approach in calcium tungstate (CaWO4) and yttrium orthosilicate (Y2SiO5), achieving cooperativities up to 0.5 for erbium dopant ensembles. Our method enables the study of
spin-
phonon interactions in complex crystalline materials, with minimal fabrication constraints. These results will facilitate the design of hybrid
quantum systems and the quest for ion-
matrix combination with enhanced
spin-
phonon coupling.
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All authors Q. Greffe, A. Hugot, S. Zhang, J. Jarreau, L. Del-Rey, E. Bonet, F. Balestro, T. Chanelière, J. J. Viennot