Quantum Gases
Floquet-induced bosonic pair condensate with unconventional symmetry
Zhizhen Chen, Jiale Huang, Mingpu Qin et al. (+1 more)
In this study, we propose a dynamical pairing mechanism other than the pair-wise interactions. Starting from a two-dimensional hard-core
boson model with periodically modulated hopping amplitude, we derive an effective Floquet
Hamiltonian with three-site interactions that are responsible for unconventional pairing between adjacent
bosons. By performing a density
matrix renormalization group study on this three-site interacting
Hamiltonian, we reveal a bosonic pair condensate with $s+id$ wave
symmetry, while the single-particle Bose-Einstein condensate is completely depleted. The experimental implementations of the proposed model on superconducting
quantum circuit have also been discussed.
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All authors Zhizhen Chen, Jiale Huang, Mingpu Qin, Zi Cai
Materials Science
Revealing the tribological stress field by using deformation twins as probes
Antje Dollmann, Alexander Dyck, Claudius Klein et al. (+3 more)
Microstructural
evolution in metallic materials feedbacks with the loading conditions and influences the life time of parts and components. Therefore, the deformation mechanisms have to be fundamentally understood. Tribological loading causes a non-trivial, position-dependent, moving stress field. We present a systematic study on the influence of the complexity of the implemented material models on the calculated stress field. For the stress field validation, results of tribological experiments on single
crystals with the activation of deformation twins are used. The resolved shear stresses calculated with the stress field models have to be highest on the experimentally identified twin systems. From this combination of modelling and experiment, it clearly follows that a stress field model considering plasticity is required. The widely used Hamilton stress field for tribological loading is limited due to only considering elastic strains. Here, the predictive quality of the stress field is sensitive to the assumed yield strength, work hardening and plastic anisotropy. Certain stress field models are close to the experimental data, but none completely replicate them. These results highlight that the model type and parameters have to be carefully determined in order to be able to predict how a metallic material deforms due to a sliding load.
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All authors Antje Dollmann, Alexander Dyck, Claudius Klein, Alexander Kauffmann, Thomas Boehlke, Christian Greiner
Statistical Mechanics
Quasistatic response for nonequilibrium processes: evaluating the Berry potential and curvature
Aaron Beyen, Faezeh Khodabandehlou and Christian Maes
We investigate how introducing slow, time-dependent perturbations to a steady, nonequilibrium process alters the expected (excess) values of important observables, such as the dynamical activity and
entropy flux. When we make a cyclic thermodynamic transformation, the excesses are described in terms of a (
geometric) Berry phase with corresponding Berry potential and Berry
curvature quantifying the response. Focussing on Markov jump processes, we show how a non-zero Berry
curvature leads to a breakdown of the thermodynamic Maxwell relations and of the Clausius heat
theorem. We also present a variant of the Aharonov-Bohm effect in which the parameters follow a curve with vanishing Berry
curvature, but the system still experiences a nonzero Berry phase. Finally, we identify (sufficient) no-localization conditions in terms of mean first-passage times under which the corresponding Berry potentials and
curvatures vanish at absolute zero, extending, for arbitrary driving, e.g., the case of vanishing heat capacity as for the Nernst postulate.
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Quantum Gases · Cross-listed from quant-ph
Antibunching in locally driven dissipative Lieb lattices
Alex Ferrier, Michał Matuszewski, Piotr Deuar et al. (+1 more)
In Lieb
lattices,
geometric frustration and destructive interference of hopping cancels the occupation of certain sites, leading to flat-band physics. Here, we show numerically how, in the driven-dissipative Bose-Hubbard (DDBH) model arranged into Lieb
lattices and related geometries, specific localised driving schemes can repurpose this interference to generate enhanced antibunching via a mechanism similar to the so-called unconventional
photon blockade.
Stochastic simulations using the positive-P method allow us to calculate occupations and second order correlations exactly for extended
lattices. We use this to optimise the parameters for the possible observation of this effect in polariton micropillar experiments. This work demonstrates the possibility of using localised driving and interference effects to generate non-trivial
quantum correlations in open
quantum lattice systems. Specifically, producing antibunching in the dark sites of the flat band system rather than the usual and less useful bunching.
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All authors Alex Ferrier, Michał Matuszewski, Piotr Deuar, Marzena H. Szymańska
Materials Science
Distinguish the Orientation of Sliding Ferroelectricity by Second-Harmonic Generation
Fengfeng Ye, Qiankun Li, Zhuocheng Lu et al. (+5 more)
As the emerging ferroelectric (FE) materials, the ultrathin two-dimensional (2D) sliding ferroelectrics without phase-matching bottleneck, usually exhibit the pronounced second harmonic generation (SHG) responses. Despite the structural polarity of sliding ferroelectrics can be precisely detected via SHG characterizations, distinguishing the orientations of sliding ferroelectricity based on SHG responses has rarely been realized, as SHG intensities for upward and downward polarization states are supposed to be same. In current work, combining computational simulations and experimental characterizations, the orientation of sliding ferroelectricity is demonstrated to be readily distinguishable via SHG responses in 2D SnP2S6 (SnP2Se6), a new sliding FE material. Specifically, owing to the unique
symmetry operation within FE-SnP2S6 (SnP2Se6), the intersection between ḩi}xxx and ḩi}yyy SHG susceptibility coefficients with opposite signs leads to the effective rotation of SHG polar directions upon switching of sliding ferroelectricity. Moreover, the remarkable dependence of SHG polar directions on the orientation of sliding ferroelectricity is further validated by experimental characterizations performed on SnP2S6
crystal in a single FE domain structural form. This work opens up the avenue for in-situ detecting the ferroelectricity orientation of 2D sliding ferroelectrics based on SHG nonlinear optical responses, and also demonstrates the controllable optical nonlinearly for new "slidetronics" applications.
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All authors Fengfeng Ye, Qiankun Li, Zhuocheng Lu, Xinfeng Chen, Yang Li, Hua Wang, Lu You, Gaoyang Gou
Mesoscale and Nanoscale Physics
A Three-Dimensional Array of Quantum Dots
Hanifa Tidjani, Dario Denora, Michael Chan et al. (+6 more)
Quantum dots can confine single electrons or holes to define
spin qubits that can be operated with high fidelity. Experimental work has progressed from linear to two-dimensional arrays of
quantum dots, enabling
qubit interactions that are essential for
quantum simulation and computation. Here, we explore architectures beyond planar geometries by constructing
quantum dot arrays in three dimensions. We realize an eight-
quantum dot system in a silicon-germanium
heterostructure comprising two stacked germanium
quantum wells, where
quantum dots are positioned at the vertices of a cuboid. Using electrostatic gate control, we load a single hole into any of the eight
quantum dots. To demonstrate the potential of multilayer
quantum dot systems, we show coherent
spin control and hopping-induced
spin rotations by shuttling between the
quantum wells. The ability to extend
quantum dot arrays in three dimensions provides opportunities for novel
quantum hardware and high-connectivity
quantum circuits.
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All authors Hanifa Tidjani, Dario Denora, Michael Chan, Jann Hinnerk Ungerer, Barnaby van Straaten, Stefan D. Oosterhout, Lucas Stehouwer, Giordano Scappucci, Menno Veldhorst
Materials Science
First-principles screening of materials with extreme effective masses
Szymon Błazucki, Junfeng Qiao, Aleksandr Poliukhin et al. (+1 more)
The effective mass of charge carriers is a fundamental descriptor of the electronic structure of materials, and can be used to assess performance in electronics applications, or to screen for thermoelectrics and transparent conductors. Here, we perform a high-throughput computational screening of approximately 20,000 experimentally known three-dimensional stoichiometric inorganics obtained from the Materials Cloud 3D structure database. By combining density-functional theory calculations and maximally localized Wannier functions, we are able to compute the full conductivity effective mass tensor for electrons and holes from the Boltzmann transport equation in the constant relaxation-time approximation. This approach captures the effects of band non-parabolicity, anisotropy, and valley multiplicity that would be neglected by standard
parabolic fittings. The screening identifies a curated set of candidates exhibiting extreme electronic properties, from ultra-low to ultra-large effective masses, these latter associated with flat-band physics. We validate the workflow by recovering established high-mobility
semiconductors and highlight promising novel candidates. Furthermore, we classify materials by their mass anisotropy and discuss the physical limits of defining a conductivity effective mass in narrow-gap regimes at room temperature. Importantly, the resulting
dataset provides a systematic roadmap to search for high-performance materials in novel chemical spaces.
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All authors Szymon Błazucki, Junfeng Qiao, Aleksandr Poliukhin, Nicola Marzari
Materials Science
Electric polarization driven by non-collinear spin alignment investigated by first principles calculations
Sergiy Mankovsky, Svitlana Polesya, Jan Minar et al. (+2 more)
We present an approach for first principles investigations on the
spin driven electric polarization in type II multiferroics. We propose a parametrization of the polarization with the parameters calculated using the Korringa-Kohn-Rostoker Green function (KKR-GF) formalism. Within this approach the induced electric polarization of a unit
cell is represented in terms of three-site parameters. Those antisymmetric with respect to
spin permutation are seen as an ab-initio based counter-part to the phenomenological parameters used within the inverse-Dzyaloshinskii-Moriya-interaction (DMI) model. Due to their relativistic origin, these parameters are responsible for the electric polarization induced in the presence of a non-collinear
spin alignment in materials with a centrosymmetric
crystal structure. Beyond to this, our approach gives direct access to the element- or site-resolved electric polarization. To demonstrate the capability of the approach, we consider several examples of the so-called type II multiferroics, for which the magneto-electric effect is observed either as a consequence of an applied
magnetic field (we use Cr$_2$O$_3$ as a prototype), or as a result of a phase transition to a
spin-spiral
magnetic state, as for instance in MnI$_2$, CuCrO$_2$ and AgCrO$_2$.
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All authors Sergiy Mankovsky, Svitlana Polesya, Jan Minar, Hongbin Zhang, Hubert Ebert
Quantum Gases · Cross-listed from gr-qc
Some considerations on BEC analogue black holes
Roberto Balbinot and Alessandro Fabbri
In this paper, dedicated to the
memory of A. Aurilia, we will review some basic features of Hawking's black hole radiation and compare them with the corresponding ones present in Bose-Einstein condensate analogue black holes.
Superconductivity
Manipulating fractional Shapiro steps in twisted cuprate Josephson junctions
Yuying Zhu, Heng Wang, Ding Zhang et al. (+1 more)
High$-$quality Josephson junctions made of twisted cuprate
superconductors offer unprecedented opportunities in addressing fundamental problems and realizing next$-$generation superconducting devices at relatively high temperatures. Whether or not the twisted cuprates possess high$-$temperature topological superconductivity remains an outstanding issue. Here, we tackle this problem via an in$-$depth study of the key predicted feature $--$ half$-$integer Shapiro steps. We show that half$-$integer Shapiro steps do occur in samples at a twist angle of 45$^\circ$ but are unstable with thermal cycling. Interestingly, fractional steps can be introduced by training the sample with a small
magnetic field or annealing with a large electrical current, attesting to a tunable current$-$phase relation (CPR) in twisted cuprates. We extend the current annealing to realize fractional steps with odd denominators too. Furthermore, half$-$integer steps can be induced in the regime that is well beyond the expectation of topological superconductivity, favoring an alternative mechanism involving trapped
vortices. Our results not only caution the direct association of half$-$integer Shapiro steps with the exotic mechanism but also open a distinct pathway toward a Josephson junction with electrically tunable CPR at high temperatures.
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All authors Yuying Zhu, Heng Wang, Ding Zhang, Qi-Kun Xue
Mesoscale and Nanoscale Physics
Real-Space Spectral Approach to Orbital Magnetization
Kevin J. U. Vidarte, Henrique P. Veiga, João M. Viana Parente Lopes et al. (+4 more)
We present a real-space spectral method for computing the orbital magnetization of
crystals. Starting from the commutator form of the orbital magnetization operator, we formulate an energy-resolved spectral function that is amenable to exact Chebyshev
polynomial expansions and yields the total magnetization upon integration up to the
Fermi level. This avoids the need for computing eigenstates and ground-state projects, providing an efficient numerical framework that is applicable to very large systems even in the presence of disorder and temperature. Our approach is benchmarked on the Haldane model, finding results that are in excellent agreement with the modern $k$-space formulation of orbital magnetization. Leveraging this technique, we extend our study to systems with uncorrelated disorder and point defects, and further show that the bulk Chern number can be directly obtained from the magnetization spectral density. These results open a promising route to investigate orbital responses and topological transitions in real-space models of
quantum materials with realistic complexity.
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All authors Kevin J. U. Vidarte, Henrique P. Veiga, João M. Viana Parente Lopes, Ramon Cardias, Aires Ferreira, Tarik P. Cysne, Tatiana G. Rappoport
Materials Science
Origin of Bright Quantum Emissions with High Debye-Waller factor in Silicon Nitride
Shibu Meher, Manoj Dey and Abhishek Kumar Singh
Silicon nitride has emerged as a promising photonic platform for integrated single-
photon sources, yet the microscopic origin of the recently observed bright
quantum emissions remains unclear. Using hybrid density functional theory, we show that the negatively charged N$_\text{Si}$V$_\text{N}$ center (NV$^{-}$) in the C$_{1h}$ configuration exhibits a linearly polarized zero-
phonon line (ZPL) at 2.46 eV, with a radiative lifetime of 9.01 ns and a high Debye-Waller (DW) factor of 33%. We further find that the C$_{1h}$ configuration is prone to a pseudo-Jahn-Teller distortion, yielding two symmetrically equivalent defect structures that emit bright, linearly polarized ZPL at 1.80 eV with a lifetime of 10.17 ns and an increased DW factor of 41%. These nitrogen-vacancy-related defects explain the origins of visible
quantum emissions, paving the way for deterministic and monolithically integrated silicon-nitride
quantum photonics.
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Materials Science
Eu-assisted enhancement of photoresponse in MBE-grown CdO/Si photodetectors
Igor Perlikowski, Eunika Zielony, Abinash Adhikari et al. (+4 more)
Doping cadmium
oxide with rare earth (RE) elements is a way to control the band gap and enhance carrier concentration and mobility. This work presents how one of REs, europium, impacts performance of CdO/Si diode. The samples were grown using
plasma-assisted molecular beam epitaxy. Doping level was modified by changing the temperature of the effusion
cell with Eu and therefore flux of Eu particles. Different dopant concentrations were confirmed by secondary ion mass spectrometry. Atomic force microscopy images revealed a grain-like surface structure of the samples with grain size increasing after rapid thermal processing (RTP). Raman spectroscopy showed that introducing Eu changes vibrational properties of CdO through intraionic anharmonicity reduction. Kelvin probe method revealed upward band bending caused by oxygen adsorption during RTP. Electrical measurements confirmed that rectifying junctions were manufactured and that they are able to produce photocurrent in the spectral range of 450-1150 nm without external voltage bias. Introducing Eu into CdO was found to increase e.g. rectifying factor and responsivity. The results show that doping CdO with Eu is a way to enhance performance of the presented zero-power-consumption photodetectors, making it a promising material for future applications in optoelectronics.
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All authors Igor Perlikowski, Eunika Zielony, Abinash Adhikari, Rafał Jakieła, Sergij Chusnutdinow, Ewa Popko, Ewa Przeździecka
Strongly Correlated Electrons · Cross-listed from nucl-th
Fermi-liquid view of viscosity in cold and dense nucleon matter
Jianing Li, Weiyao Ke and Jin Hu
We develop a framework to calculate transport properties in cold, dense relativistic quasiparticle system within the
Fermi-
liquid theory at the mean-field level. Building on our previous study J. Li et al. [Phys. Rev. C 111, 044904 (2025)], we start from the linearized relativistic Boltzmann equation tailored to quasiparticles with medium-dependent dispersion relation and implement Landau matching conditions, proving that the bulk viscosity is manifestly nonnegative. A low-temperature expansion then yields leading-order ($T/\mu^*$) expressions for the shear ($\eta$) and bulk ($\zeta$) viscosities, where the behavior $\zeta/\eta \propto (T/\mu^*)^4$ in the degenerate regime is found to be robust against quasiparticle mass correction. We couple the kinetic framework to a Walecka-type mean-field equation of state and compute $\eta$ and $\zeta$ for cold, dense nucleon matter. The transport properties of nucleonic matter in the degenerate regime can be relevant for intermediate beam-energy
nuclear experiments.
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Soft Condensed Matter
Exact results and instabilities in the harmonic approximation of active crystals
Connor Roberts and Gunnar Pruessner
Condensates of active particles such as
cells form almost-crystalline
lattices which play a central role in many biological systems. Typically, their properties have been determined merely by analogy to the rather trivial one-dimensional case, leaving a gap between experimentally accessible observables and suitable theoretical models. Within a harmonic approximation, we characterise analytically a two-dimensional triangular
lattice of active particles that interact with their nearest neighbours through a general pair potential, obtaining exact expressions for the correlators. We study this "active
crystal" as a means of characterising active matter in the dense phase. Our treatment correctly approximates arbitrary pair potentials, rather than demanding an unphysical non-singular bilinear form. We retain "off-diagonal" terms that are routinely neglected despite quantifying the anisotropy of the particles' local potential. From the exact expressions for the correlation
matrices, we derive exact results that shed light on the presence (or absence) of crystalline order. We further calculate the mean-squared particle separation, energy,
entropy production rate and the onset of a pressure-induced instability resulting in the breakdown of the harmonic approximation. The
entropy production rate is found to have a general form that is valid for generic active particles and
lattice geometries, while resembling that of non-interacting "active modes".
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Materials Science
Defect-Limited Efficiency of Pnictogen Chalcohalide Solar Cells
Cibrán López, Seán R. Kavanagh, Pol Benítez et al. (+4 more)
Pnictogen chalcohalides (MChX) have recently emerged as promising nontoxic and environmentally friendly photovoltaic absorbers, combining strong light absorption coefficients with favorable low-temperature synthesis conditions. Despite these advantages and reported optimized morphologies, device efficiencies remain below 10%, far from their ideal radiative limit. To uncover the origin of these performance losses, we present a systematic and fully consistent first-principles investigation of the defect chemistry across the Bi-based chalcohalide family. Our results reveal a complex defect landscape dominated by chalcogen vacancies of low formation energy, which act as deep nonradiative recombination centers. Despite their moderate charge-carrier capture coefficients, the high
equilibrium concentrations of these defects reduce the theoretical maximum efficiencies by 6% in BiSeI and by 10% in BiSeBr. In contrast, sulfur vacancies in BiSI and BiSBr are comparatively benign, presenting smaller capture coefficients due to weaker electron-
phonon coupling. Interestingly, despite its huge nonradiative charge-carrier recombination rate, BiSeI presents the best conversion efficiency among all four compounds owing to its most suitable bandgap for outdoor photovoltaic applications. Our findings identify defect chemistry as a critical bottleneck in MChX
solar cells and proposes chalcogen-rich synthesis conditions and targeted anion substitutions as effective strategies for mitigation of detrimental vacancies.
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All authors Cibrán López, Seán R. Kavanagh, Pol Benítez, Edgardo Saucedo, Aron Walsh, David O. Scanlon, Claudio Cazorla
Soft Condensed Matter
Cytoplasmic flow induced by a rotating wire in living cells: Magnetic rotational spectroscopy and finite element simulations
Charles Paul Moore, Foad Ghasemi and Jean-François Berret
Recent studies have highlighted intracellular viscosity as a key biomechanical property with potential as a biomarker for cancer
cell metastasis. In the context of cellular mechanobiology,
magnetic rotational spectroscopy (MRS), which employs rotating
magnetic wires of length\,! = 2-8 $\mu$m to probe cytoplasmic rheology, has emerged as an effective method for quantifying intracellular viscoelasticity. This study examines microrheology data from three breast epithelial
cell lines, MCF-10A, MCF-7, and MDA-MB-231, along with new data from HeLa cervical cancer
cells. Here, MRS is combined with finite element simulations to characterize the flow field induced by wire rotation in the cytoplasm. COMSOL simulations performed at low Reynolds numbers show that the flow velocity is localized around the wire, and display characteristic dumbbellshaped profiles. For wires representative of MRS experiments in
cells, the product of shear rate and cytoplasmic relaxation time (”$ with $ ~ 1 s) remains below unity, indicating that the flow occurs within the linear regime. This outcome confirms that MRS can reliably measure the zeroshear viscosity of the intracellular medium in living
cells. This study also demonstrates that integrating MRS intracellular measurements with COMSOL simulations significantly improves the reliability of in vitro assessments of cytoplasmic mechanical properties.
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Soft Condensed Matter
Massart iron oxide nanoparticles in mechanobiology
Myriam Reffay, Gilles Tessier and Jean-François Berret
Magnetic nanoparticles (MNPs) derived from the Massart coprecipitation method have played a pioneering role in bridging materials science and biology. Their
magnetic moment and nanoscale dimensions have long enabled applications in
magnetic resonance imaging, targeted drug delivery, separation technologies, and hyperthermia. Beyond these well-established uses, a growing research direction has emerged at the interface of physics and biology: the application of MNPs in mechanobiology, the study of how mechanical forces regulate cellular and tissue functions. This review examines how Massart MNPs can be used to generate, transmit, and measure forces within living systems. Particular
attention is given to interfacial control through advanced surface chemistries, which ensure colloidal stability, minimize toxicity, and preserve the nanoscale integrity of the particles. We also show that the robustness and scalability of Massart synthesis make it ideally suited to the production of biocompatible nanomaterials in quantities required for comprehensive biological studies. Two complementary approaches are discussed. The first exploits MNP assemblies that arise spontaneously within
cells, in the form of endosomes. These compartments enable the application of controlled
magnetic forces to study both the formation of reconstructed tissues and organoids, and their viscoelastic response. The second focuses on micrometric
magnetic wires fabricated from MNPs, used in active microrheology to probe the cytoplasm of living
cells over a wide frequency range. Together, these approaches illustrate how MNP assemblies can accurately quantify cellular and tissue mechanics, providing new opportunities for mechanobiological studies and enabling the development of novel readouts of cellular mechanics with potential diagnostic applications.
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Materials Science · Cross-listed from cs.CV
QuantumCanvas: A Multimodal Benchmark for Visual Learning of Atomic Interactions
Can Polat, Erchin Serpedin, Mustafa Kurban et al. (+1 more)
Despite rapid advances in molecular and materials machine learning, most models still lack physical transferability: they fit correlations across whole molecules or
crystals rather than learning the
quantum interactions between atomic pairs. Yet bonding, charge redistribution, orbital hybridization, and electronic coupling all emerge from these two-body interactions that define local
quantum fields in many-body systems. We introduce QuantumCanvas, a large-scale
multimodal benchmark that treats two-body
quantum systems as foundational units of matter. The
dataset spans 2,850 element-element pairs, each annotated with 18 electronic, thermodynamic, and
geometric properties and paired with ten-channel image representations derived from l- and m-resolved orbital densities, angular field transforms, co-occupancy maps, and charge-density projections. These physically grounded images encode spatial, angular, and electrostatic
symmetries without explicit coordinates, providing an interpretable visual modality for
quantum learning. Benchmarking eight architectures across 18 targets, we report mean absolute errors of 0.201 eV on energy gap using GATv2, 0.265 eV on HOMO and 0.274 eV on LUMO using EGNN. For energy-related quantities, DimeNet attains 2.27 eV total-energy MAE and 0.132 eV repulsive-energy MAE, while a
multimodal fusion model achieves a 2.15 eV Mermin free-energy MAE. Pretraining on QuantumCanvas further improves convergence stability and generalization when fine-tuned on larger
datasets such as QM9, MD17, and CrysMTM. By unifying orbital physics with
vision-based representation learning, QuantumCanvas provides a principled and interpretable basis for learning transferable
quantum interactions through coupled visual and numerical modalities.
Dataset and model implementations are available at https://github.com/KurbanIntelligenceLab/QuantumCanvas.
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All authors Can Polat, Erchin Serpedin, Mustafa Kurban, Hasan Kurban
Mesoscale and Nanoscale Physics
Interatomic spin-orbit interaction in a $p$-orbital helical atomic chain
Takemitsu Kato, Yasuhiro Utsumi, Ora Entin-Wohlman et al. (+1 more)
We derive the interatomic
spin-orbit interaction (SOI) from a helical atomic chain composed of $p$-orbitals with intra-atomic SOI, which exhibits a helical state–a potential origin of the
chiral-induced
spin selectivity (CISS) effect. In this model, a strong
crystal field in the tangential direction of the helix leads to the formation of energetically separated $\sigma$- and $\pi$-bands. In the second-order process, a
spin in the $\sigma$-orbital virtually hops to the $\pi$-orbital, flips its direction due to intra-atomic SOI, and then hops back to the $\sigma$-orbital in the neighboring atom due to the misalignment of $p$-orbitals along the helix. This process induces an interatomic SOI in the $\sigma$-band, which takes the form of a Rashba-type SOI generated by an electric field normal to the helical axis. The magnitude of the SOI is proportional to the
curvature, the hopping energy, the intra-atomic SOI energy, and inversely proportional to the
crystal field strength. The second-order process also induces long-range second-nearest-neighbor hoppings. We analytically derive the
spin-split band structure in the zero-torsion limit.
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All authors Takemitsu Kato, Yasuhiro Utsumi, Ora Entin-Wohlman, Amnon Aharony
Strongly Correlated Electrons
Disorder Suppression of Charge Density Waves in the Honeycomb Holstein Model
Guangchao Li, Lifei Zhang, Tianxing Ma et al. (+2 more)
The formation of charge-density-wave order in Dirac
fermion systems via electron-
phonon coupling represents a significant topic in condensed matter physics. In this work, we investigate this phenomenon within the Holstein model on the honeycomb
lattice, with a specific focus on the effect of disorder. While the interplay between electron-electron interactions and disorder has long been a central theme in the field, recent
attention has increasingly turned to the combined influence of disorder and electron-
phonon coupling. Using determinant
quantum Monte Carlo simulations, we concentrate on the phase transitions of charge-density-wave order on the honeycomb
lattice. Disorder is introduced through the random hopping of electrons in the system, which can localize electrons via the Anderson effect. Our primary result is that disorder suppresses the charge-density-wave phase, and the interplay between disorder and electron-
phonon interactions extends the phase area. We also determine the transition temperature \(\beta_c\) to the ordered phase as a function of the electron-
phonon coupling. Additionally, we observed a suppression of electron kinetic energy and dc conductivity under disorder, highlighting the role of Anderson localization in the degradation of electronic transport. These findings offer significant theoretical insight into the stability and critical phenomena of correlated phases in disordered two-dimensional systems.
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All authors Guangchao Li, Lifei Zhang, Tianxing Ma, Qionglin Dai, Lufeng Zhang
Soft Condensed Matter
Non-Markovian dynamics in ice nucleation
Pablo Montero de Hijes, Sebastian Falkner and Christoph Dellago
In simulation studies of crystallisation, the size of the largest crystalline
nucleus is often used as a reaction coordinate to monitor the progress of the nucleation process. Here, we investigate, for the case of homogeneous ice nucleation, whether the
nucleus size exhibits Markovian dynamics, as assumed in classical nucleation theory. Using 300 independent nucleation trajectories generated by molecular dynamics, we evaluate the mean recurrence time required to reach selected values of the largest
nucleus size. Early recurrences consistently take longer than later ones, revealing a clear history dependence and thus non-Markovian dynamics. To identify the slow modes underlying this behaviour, we analyse several structural descriptors of the
nucleus, observing subtle but systematic differences between
nuclei at early and late recurrences. By training a neural network on 2,700 short trajectories to learn the committor, we identify relevant collective variables. Based on these features, symbolic regression provides a compact approximation of the committor, i.e., an improved reaction coordinate, which we subsequently test for Markovianity.
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Materials Science
Optical refractive index measurements of AlGaAs at high temperature for fully automated molecular beam epitaxy growth of Bragg mirrors
Pierre Gadras, Léo Bourdon, Antoine Fées et al. (+3 more)
In-situ measurement is a key feature to better understand and precisely control the growth of complex structures, such as vertical-cavity surface-emitting
lasers. In this work, we are showing the precise measurement of optical indices of AlGaAs at 600 {\textdegree}C over a wide spectral range (450–1400 nm). To do so, in-situ spectral reflectance measurement is used, combined with ex-situ layer thickness and composition measurement by x-ray diffraction enabling for precise determination of the optical indices with an accuracy better than 1%. To validate our measurements, we realized the complete automation of the growth of a GaAs/AlAs 940 nm-DBR by molecular beam epitaxy, without the need to pre-calibrate
cells fluxes. The fabricated DBR shows a deviation of 0.2 nm of the stop-band central-wavelength compared to the targeted one. This approach holds significant interest for the III–V
semiconductor community and epitaxial growth techniques.
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All authors Pierre Gadras, Léo Bourdon, Antoine Fées, Karim Ben Saddik, Guilhem Almuneau, Alexandre Arnoult
Statistical Mechanics
Path-integrals and optimal paths for the fractional Ornstein-Uhlenbeck process
Bing Miao, Gleb Oshanin and Luca Peliti
We derive the path-integral representation of the fractional Ornstein-Uhlenbeck process driven by Riemann-Liouville fractional Gaussian noise, for both the subdiffusive and superdiffusive regimes. We express the corresponding action, which is a quadratic functional of individual trajectories of the process, in two alternative but equivalent forms: either as a fractional integral or as a double integral with a nonlocal kernel. Moreover, we determine in closed form the optimal (action-minimizing) paths conditioned to reach a prescribed point at a fixed time moment and discuss their behavior, which appears to be non-intuitive for subdiffusive processes in the presence of a strong confining potential.
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Materials Science
Silver Alloyed Wide Bandgap (Ag,Cu)(In,Ga)S2 Thin Film Solar Cells With 15.5% Efficiency
Yucheng Hu, Ece Washbrook, Arivazhagan Valluvar Oli et al. (+14 more)
Sulfide chalcopyrite Cu(In,Ga)S2 (CIGS) is a wide bandgap
semiconductor suitable for the top
cell of a tandem
solar device. Here we demonstrate significant improvements in absorber quality by alloying with Ag to form (Ag,Cu)(In,Ga)S2 (ACIGS) absorbers. We report the Ag alloying effect on compositional, structural, and optoelectronic properties of absorbers. We demonstrate suppressed bulk recombination and improved carrier lifetime in ACIGS, as a result of improved grain size, porosity reduction and defect passivation. We also show that Ag alloying flattens the Ga gradient. Consideration of this impact of Ag will be necessary in future engineering of the Ga profile to maximize charge carrier collection and avoid interface recombination. Exploiting the beneficial effects of Ag alloying, we report a wide bandgap (1.58 eV) ACIGS
solar cell with a high power conversion efficiency of 15.5% and a large open-
circuit voltage (VOC) of 948 mV, improving on the reference pure CIGS
solar cell, with an 11.2% efficiency and an 821 mV VOC. Ag alloying is a useful route to further increase the efficiency of CIGS
solar cells and future tandem devices.
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All authors Yucheng Hu, Ece Washbrook, Arivazhagan Valluvar Oli, Andrea Griesi, Yurii P. Ivanov, Mariam Pelling, Simon M. Fairclough, Kulwinder Kaur, Michele Melchiorre, Adam Hultqvist, Tobias Törndahl, Wolfram Hempel, Wolfram Witte, Giorgio Divitini, Susanne Siebentritt, Rachel A. Oliver, Gunnar Kusch
Statistical Mechanics
The stochastic discrete nonlinear Schrödinger equation: microscopic derivation and finite-temperature phase transition
Mahdieh Ebrahimi, Barbara Drossel and Wolfram Just
We study a
stochastic version of the one-dimensional discrete nonlinear Schrödinger equation (DNSE), which is derived from first principles, and thus possesses all the properties required by statistical mechanics, such as detailed balance and the H-
theorem. The
stochastic version shows disordered and localised dynamics, and displays a corresponding phase transition at a finite temperature value. The phase transition can be captured in a quantitative way by a mean-field type approach. The corresponding coarsening dynamics shows an unexpected dependence on the noise strength, which is reminiscent of
stochastic resonance. The phase transition is linked with negative temperature phase transitions, which have been reported recently for the
Hamiltonian dynamics of the DNSE. Our approach gives a clue to how these negative temperature phase transitions can be implemented in experimental setups, which are inevitably coupled to a positive temperature heat bath.
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Materials Science · Cross-listed from physics.optics
Effects of thermal annealing and film thickness on the structural and optical properties of indium-tin-oxide thin films
Ding Xu, Wen Zhou, Yuxin Du et al. (+3 more)
Indium-tin
oxide (ITO) is a crucial functional layer for the optoelectronic applications, such as non-volatile color display thin films based on the ITO/phase-change material (PCM)/ITO/reflective metal multilayer structures on a silicon substrate. In addition to non-volatile color tuning by PCMs, thermally induced crystallization may alter the optical properties of ITO layers as well. But the potential change in color of the ITO layers is not considered so far. In this work, we investigate the structural and optical properties of ITO thin films via X-ray diffraction, spectroscopic ellipsometry and ultraviolet-visible spectrophotometry measurements. After thermal annealing at 250 {\deg}C, the ITO thin films of 15-100 nm get crystallized with strong changes in refractive index n and extinction coefficient k in the visible light range. However, for the 5-nm ITO thin film, crystallization is only observed after thermal annealing at 350 {\deg}C and the change in color is limited upon phase transition. We provide a colormap of the ITO/platinum/silicon structure in terms of the annealing temperature (150-350 {\deg}C) and ITO film thickness (5-100 nm). Our work suggests that the intrinsic change in colors of ITO layers should also be considered for the PCM-based reconfigurable display application.
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All authors Ding Xu, Wen Zhou, Yuxin Du, Junying Zhang, Wei Zhang, Jiangjing Wang
Materials Science
An Investigation of Thermal Properties of Cu-Au Janus Nanoparticles
Mehmet Akif Cebeci, Hatice Zor Oguz, Sevgi Ozdemir Kart et al. (+1 more)
In this paper, the thermal and structural properties of Cu-Au (Copper-Gold) Janus nanoparticles with a diameter of 5 nm are investigated by using molecular dynamics (MD) simulations within the interactions defined by the many-body embedded atom model (EAM). A set of nanoparticle models has been constructed, with varying Cu and Au ratios. MD method is carried out to calculate the melting temperature, heat capacity, radial distribution function (RDF), Lindemann index, mean square displacement (MSD), and
diffusion coefficients of these models. The findings demonstrate that nanoparticles rich in Cu exhibit a higher melting temperature and more defined phase transitions. In contrast, structures rich in gold exhibited reduced melting temperatures and showed surface-initiated melting behaviours. MD study highlights that the thermal stability and atomic mobility of Cu-Au Janus nanoparticles depend on the composition ratio and the dispersion of materials.
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All authors Mehmet Akif Cebeci, Hatice Zor Oguz, Sevgi Ozdemir Kart, Hasan Huseyin Kart
Mesoscale and Nanoscale Physics
Field-free diode effects in one-dimensional superconductor: a complex interplay between Fulde-Ferrell pairing and altermagnetism
SVS Sai Ruthvik and Tanay Nag
We investigate the emergence of nonreciprocal dissipationless supercurrents in one-dimension manifested through the superconducting diode effect (SDE) and the Josephson diode effect (JDE) in the absence of any external
magnetic field, where inversion
symmetry (IS) and time-reversal
symmetry (TRS) can be intrinsically broken by
spin-orbit coupling (SOC), and altermagnetism (AM), respectively. We investigate Ising and Rashba SOC separately in two models where two-component AM, assembled with crystallographic angle, can lead to qualitatively similar indirect band-gap closing and non-reciprocal supercurrent in a Fulde-Ferrell (FF)
superconductor. Interestingly, in the absence of the above SOCs, SDE persists and the sign of efficiency can be altered by tuning the angle only. Parallel
spin components with complementary momentum functions, ensuring the breaking of IS and TRS, can induce SDE in the presence of FF pairing. Continuing the analysis in the context of JDE, we explore the interplay between SOCs and AM with the p-wave and Fulde-Ferrell superconductivity in three different setups. The bulk bands contributes to the non-reciprocity in the case of p-wave superconductivity while JDE is dominated by Andreev bound states for FF superconductivity. Importantly, JDE continues to exist due to finite momentum Cooper pair even without AM and SOC unlike the p-wave superconductivity. The sign of JD efficiency can be tuned with angle for p-wave superconductivity while absence of such sign reversal is a hallmark signature of FF superconductivity. Similar to SDE, parallel
spin components in conjunction with p-wave superconductivity can lead to JDE that can also be mediated by only FF pairing in the absence of SOC and AM.
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Quantum Gases
Role of impurity statistics and medium constraints in polaron-polaron interactions
Jesper Levinsen, Francesca Maria Marchetti, Olivier Bleu et al. (+1 more)
We consider the behavior of a small density of mobile
impurities (polarons) immersed in a
quantum gas, a generic scenario that can be realized in cold atomic gases,
liquid helium mixtures, and doped
semiconductors. We present a unified theoretical framework for understanding polaron quasiparticles beyond the single-
impurity limit, and we identify two key factors that control the polaron-polaron interactions: (i) the statistics of the
impurities, including whether or not they are degenerate, and (ii) the constraints on the medium response, i.e., whether the medium density or chemical potential is held fixed. By constructing wave functions for two bosonic, fermionic, or distinguishable
impurities immersed in a Bose or
Fermi gas, we derive rigorous results for the polaron interactions in the limit of weak
impurity-medium coupling. We furthermore obtain an exact relationship between the polaron interactions at fixed medium density and at fixed chemical potential, a result which is valid for arbitrary interaction strength. Our work provides an important guide for understanding experiments, and it acts as a starting point for future strong-coupling theories of polaron interactions that capture all of the effects identified in this work.
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All authors Jesper Levinsen, Francesca Maria Marchetti, Olivier Bleu, Meera M. Parish