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Physics Condensed Matter

cond-mat Watch Condensed Matter

Monday 26 January

Mesoscale and Nanoscale Physics

Tunneling signatures of interband coherence in dilute exciton condensates

Kryštof Kolář and Felix von Oppen

We theoretically investigate signatures of exciton condensation and the underlying interband coherence in scanning tunneling microscopy. We consider both monolayer and bilayer condensates in the regime of a dilute condensate of tightly bound excitons. For monolayer condensates, interband coherence is directly encoded in spatially oscillating contributions to the tunneling conductance, which break the underlying lattice symmetry. We show how scanning tunneling microscopy allows one to extract the exciton wavefunction. For bilayer condensates, we show that the formation of the exciton insulator is signaled by the emergence of a characteristic peak in the tunneling conductance, which can be used to extract the (local) exciton density. Our results are based on analytical considerations using a systematic solution of the mean-field equations in powers of the exciton density as well as numerical calculations.
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Materials Science

Understanding Interface Stability in RENi2/Ni through First-Principles Calculations

Yuta Yahagi and Yumi Katasho

Crystallographic orientation analysis revealed that DyNi2 grew epitaxially on Ni, whereas NdNi2 does not. To elucidate the microscopic origin of this contrasting behavior, we constructed atomistic models of Ni/Rare-earth (RE)Ni2 interfaces with well-defined crystallographic alignment and performed first-principles calculations based on density functional theory (DFT). The computed interfacial energies exhibit a clear correlation with lattice mismatch: larger mismatch leads to higher interfacial energy and reduced interface stability. Consequently, Ni/DyNi2 exhibits a significantly lower interfacial energy than Ni/NdNi2, consistent with experimental observations. A comparison between interfacial and strain energies for Ni/RENi2 (RE = Sc, Y, Nd, Gd, Dy, and Lu) reveals that the elemental dependence of interfacial stability is dominated by elastic strain rather than chemical bonding. Based on this insight, we developed a simple regression model using the absolute lattice mismatch as a descriptor, enabling qualitative predictions of stability for Ni/RENi2 interfaces with RE other than those examined in DFT.
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Materials Science

Accurate semiempirical analytical formulas for spontaneous polarization by crystallographic parameters of SrTiO3-BaTiO3 system by ab initio calculations

Yukio Watanabe

Spontaneous polarizations (PSs) of BaTiO3 and SrTiO3 under various conditions are calculated ab initio using different exchange-correlation functionals. The extensive theoretical sets of PS vs. ion positions are found to lie on a single curve, despite the chemical differences and the wide variations of PS and lattice parameters. This uncovers accurate simple analytical formulas of PS of SrTiO3-BaTiO3 system expressed by ion positions; a single formula predicts both macroscopic and atomic-scale PS of SrTiO3, BaTiO3 and SrTiO3-BaTiO alloys. The accuracy of the formula is demonstrated by the application to experiments, BaTiO3-SrTiO3 (-CaTiO3) alloys, Sr4Ti4O12 with PS // a-axis, a parallel domain, and a headon domain. In addition, the present results verify empirically that oxygen displacement is the primary identifier and the origin of PS of SrTiO3 and BaTiO3 and indicate that BaTiO3 and SrTiO3 may transforms into new state by an extremely large strain, e.g., -3%. Furthermore, the earlier prediction of headon domain without aid of defects was confirmed. The present procedures for finding formulas can be applied to other materials.
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Soft Condensed Matter

Programming Nonlinear Interfacial Mechanics of Synthetic Cells: Lipid Geometry and DNA Nanostructures

Kazutoshi Masuda and Miho Yanagisawa

Soft interfaces formed by lipid membranes are fundamental to living cells, synthetic cells, and membrane-based soft materials. However, a quantitative framework linking molecular organization with nonlinear interfacial mechanics remains elusive. Here, we establish an analytical framework that captures the nonlinear elastic response of lipid-membrane-coated synthetic cells under micropipette aspiration. Incorporating both area stretching and curvature bending enables the model to quantitatively reproduce the complete pressure-displacement response within the small-deformation regime. This approach reduces interfacial mechanics to two parameters: the in-plane area-stretching modulus and an out-of-plane bending-related term. Using this unified framework, we experimentally demonstrate that nonlinear interfacial mechanics can be programmed by altering the molecular geometry and effective dimensionality of adsorbed elements. The lipid molecular shape and curvature-dependent packing regulate in-plane stiffness, while DNA nanostructures, the other adsorbed element, introduce an orthogonal control axis via dimensionality: isolated motifs primarily enhance area stretching, whereas three-dimensional network architectures markedly reinforce bending resistance. Together, these results establish a general molecular design principle for programming interfacial mechanics and provide a quantitative foundation for engineering mechanically tunable synthetic cells and soft interfaces.
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Materials Science

Functionalities of Au2O, Au2O3, Au2O3-x, and nanosheets, including spontaneous polarization, using DFT and hybrid functional

Yukio Watanabe

We used density functional theories (DFT) to investigate the properties of Au2O and Au2O3-x (x = 00.08) to reveal their remarkable functionalities. Hybrid functional theories accurately estimate the band gap (Eg) of oxides, and the present hybrid functional calculations determined Eg values of 0.96 eV for Au2O and 2.86 eV for Au2O3, which is >300% of the commonly accepted Eg of Au2O3 (0.85 eV). Moreover, we discovered spontaneous polarization (PS) in Au2O3, which is unusually large and advantageous for catalysis. The PS was retained even in 2-nm-thick Au2O3 nanosheets, similar to hyperferroelectric, generating a potential of 0.6 eV despite screening caused by surface reconstruction, which is a novel screening mechanism. Below a thickness of 0.8 nm, the PS vanished, and inversion symmetry emerged at 0.4 nm, suggesting a new approach to finding a paraelectric phase. Au2O was supersoft under shear distortion.
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Statistical Mechanics · Cross-listed from astro-ph.GA

In-depth analysis of bar formation mechanisms of disk galaxies in halos of different concentrations

T. Worrakitpoonpon

We use $N$-body simulations to investigate the distinct bar formation processes in disks residing in halos of various concentrations. In a highly concentrated halo, the bar development is limited by the dominant multi-arm modes as a result of the swing amplification in the early stage. Only after the multi-arm modes decay, the bar growth proceeds mechanically owing to the particle trapping in continuation of that bar seed. In this scheme, the corotation resonance of the bar modes does not come into play at all, justified by a low amount of disk-halo angular momentum transfer and a modestly decreasing bar pattern speed. On the other hand, although reducing the halo concentration suggests the reduction of the preferred swing-amplified modes to be bi-symmetric, the bar formation in a lowly concentrated halo does not involve the swing amplification at all. Rather, the fast-growing linearly unstable bar modes of a single uniform frequency is solely the governing factor, attributed to a mild shearing. The bar modes trigger the corotation resonance since the beginning and such resonance is maintained until the end, which leads to a high amount of angular momentum transfer and a fast slowdown. For the intermediate halo concentration, the kinematical analyses of multiple non-axisymmetric modes suggests that the linear modes, the swing amplification, and the particle trapping are all present in the evolution chronology. To specify bars formed in the different halo concentrations, full analyses of the isophotal shape, the radial Fourier amplitude, and the resonance diagram can be of use.
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Materials Science

Magnetic field-induced non-trivial Lifshitz transition in TaCo2Te2

Suman Kalyan Pradhan, Xiaoming Ma, Jicheng Wang et al. (+14 more)

Magnetic-field-driven Lifshitz transitions are typically considered zero-temperature phenomena involving Fermi-surface reconstruction without symmetry breaking. Here, we report an unconventional Lifshitz transition in TaCo2Te2 that emerges exclusively within a narrow finite-temperature window under cooperative tuning by both temperature and magnetic field. Bulk-sensitive transport and thermoelectric measurements demonstrate continuous Fermi-surface renormalization at low temperatures, where the transition is sharply triggered by a critical magnetic field. Crucially, neutron diffraction reveals the absence of structural or magnetic phase transitions, while angle-resolved photoemission spectroscopy shows no spectral anomalies in electronic structure without magnetic field. These observations constrain the mechanism to a Zeeman-driven process invisible to equilibrium probes, establishing a paradigm where Fermi-surface topology is jointly controlled by temperature and magnetic field.
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All authors Suman Kalyan Pradhan, Xiaoming Ma, Jicheng Wang, Weiqi Liu, Yue Dai, Wenxing Chen, Xiaobai Ma, Wenyun Yang, Yu Wu, Zhaochu Luo, Raktim Datta, Arnab Bera, Samik DuttaGupta, Jinbo Yang, Yanglong Hou, Chang Liu, Rui Wu

Statistical Mechanics

Non-equilibrium symmetry of cyclic first-passage times

Daniel Maria Busiello, Shiling Liang and Simone Pigolotti

We study the sum of first passage times along an arbitrary cycle made up of N>2 states of a small physical system. We show that, if the system is at thermodynamic equilibrium, this sum follows the same probability distribution regardless of whether the cycle is explored clockwise or counterclockwise. Out of equilibrium, the distributions of clockwise and counterclockwise cyclic first passage times are related by a detailed fluctuation theorem. This result descends from a symmetry of clockwise and counterclockwise trajectories, which combines time reversal with swapping portions of the trajectories. We then relate the entropy produced along the cycle with the entropy production of the whole system using large deviation theory. Our results reveal a novel symmetry in stochastic systems, of potential broad applicability in non-equilibrium physics.
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Soft Condensed Matter

Chain-Length-Dependent Partitioning of 1-Alkanols in Raft-Like Lipid Membranes

Anirban Polley

Although 1-alkanols are widely used as anesthetics and membrane-active agents, the molecular basis of their chain-length-dependent cutoff behavior remains unclear. Here, we perform extensive atomistic molecular dynamics simulations to investigate the partitioning of 1-alkanols with varying chain lengths in a raft-like lipid bilayer composed of dipalmitoylphosphatidylcholine (DPPC), dioleoylphosphatidylcholine (DOPC), and cholesterol (Chol), which exhibits coexistence of liquid-ordered ($l_o$) and liquid-disordered ($l_d$) domains. We observe pronounced lateral heterogeneity in alkanol distribution, membrane thickness, number density, and lateral pressure profiles across coexisting phases. A distinct cutoff chain length, $n_{cutoff}=12$, is identified: alkanols with $n<n_{cutoff}$ preferentially partition into DOPC-rich $l_d$ domains, whereas alkanols with $n \ge n_{cutoff}$ preferentially localize within DPPC- and cholesterol-rich $l_o$ domains. This chain-length-dependent redistribution is accompanied by systematic reductions in the lateral pressure profile, membrane compressibility, and bending rigidity of the bilayer. The results provide a detailed molecular characterization of how alkanol chain length modulates membrane structure and mechanical response in laterally heterogeneous lipid membranes.
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Materials Science · Cross-listed from physics.optics

Pulse-driven photonic transitions and nonreciprocity in space-time modulated metasurfaces

Zeki Hayran, John B. Pendry, Prasad P. Iyer et al. (+1 more)

Time-varying photonic systems open new possibilities for controlling light, enabling photonic time crystals, time reflection and refraction, frequency conversion, synthetic gauge fields, optical nonreciprocity, among others. These effects emerge from the dynamic modulation of optical properties, which can mediate photonic transitions between eigenstates of different frequencies and/or wavevectors. To achieve such transitions, conventional approaches rely on periodic modulation schemes that demand ultrafast modulation rates and continuous energy input, posing significant practical challenges at optical frequencies. Here, we demonstrate that periodic-modulation-driven photonic transitions within the radiation continuum can be effectively mimicked using a single-period ultrafast pulse modulation, eliminating the need for sustained continuous modulation. By leveraging dispersion engineering in metasurfaces to tailor the density of states in the radiation continuum, we achieve controlled frequency transitions and theoretically demonstrate strong nonreciprocity for free-space waves as a key application. Our findings may guide future experimental research on time-varying photonics using materials such as transparent conductive oxides and semiconductors, expanding the possibilities for ultrafast and reconfigurable optical technologies. More broadly, our work may establish a practical and energy-efficient framework for dynamic photonic systems, with potential applications ranging from spatio-temporal wavefront manipulation to photonic computing and ultrafast signal processing.
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All authors Zeki Hayran, John B. Pendry, Prasad P. Iyer, Francesco Monticone

Materials Science

Thicker amorphous grain boundary complexions reduce plastic strain localization in nanocrystalline Cu-Zr

Esther C. Hessong, Nicolo Maria della Ventura, Tongjun Niu et al. (+6 more)

Amorphous grain boundary complexions have been shown to increase the plasticity of nanocrystalline alloys as compared to ordered grain boundaries. Here, the effect of an important structural descriptor, amorphous complexion thickness, on the plasticity and failure modes of nanocrystalline Cu-Zr is studied with in-situ compression testing, with over 50 micropillars tested. Two model materials were created that differ only in their complexion thickness, with one having a thicker complexion population than the other. The sample with thinner complexions was more likely to experience non-uniform plastic deformation in the form of localized plastic flow or shear banding. In contrast, the sample with thicker complexions displayed more homogeneous plasticity and higher damage tolerance; thicker amorphous complexions suppress localization by absorbing defects. This work demonstrates that increasing complexion thickness can be beneficial for stable plastic flow in nanocrystalline alloys, by improving resistance to strain localization and premature failure.
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All authors Esther C. Hessong, Nicolo Maria della Ventura, Tongjun Niu, Daniel S. Gianola, Hyosim Kim, Nan Li, Saryu Fensin, Brad L. Boyce, Timothy J. Rupert

Sunday 25 January

Materials Science · Cross-listed from nucl-th

"Observations on the possible electromagnetic nature of nucleon interactions and pions" – historical manuscript from 1969 by B. W. Ninham and C. Pask

Mathias Boström and Drew F. Parsons

This manuscript presents an historical perspective prepared by Barry Ninham and Colin Pask in 1969 on the connection between quantum electrodynamics theory and nucleon interactions. A new theory of strong interactions based on electromagnetic considerations is proposed. Energy and force range magnitudes are correctly given. A new theory of the pion emerges and the pion mass and lifetime are calculated. No strong interaction coupling constant is required.
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Soft Condensed Matter

Autonomous Multi-Agent AI for High-Throughput Polymer Informatics: From Property Prediction to Generative Design Across Synthetic and Bio-Polymers

Mahule Roy, Adib Bazgir, Arthur da Silva Sousa Santos et al. (+1 more)

We present an integrated multiagent AI ecosystem for polymer discovery that unifies high-throughput materials workflows, artificial intelligence, and computational modeling within a single Polymer Research Lifecycle (PRL) pipeline. The system orchestrates specialized agents powered by state-of-the-art large language models (DeepSeek-V2 and DeepSeek-Coder) to retrieve and reason over scientific resources, invoke external tools, execute domain-specific code, and perform metacognitive self-assessment for robust end-to-end task execution. We demonstrate three practical capabilities: a high-fidelity polymer property prediction and generative design pipeline, a fully automated multimodal workflow for biopolymer structure characterization, and a metacognitive agent framework that can monitor performance and improve execution strategies over time. On a held-out test set of 1,251 polymers, our PolyGNN agent achieves strong predictive accuracy, reaching R2 = 0.89 for glass-transition temperature (Tg ), R2 = 0.82 for tensile strength, R2 = 0.75 for elongation, and R2 = 0.91 for density. The framework also provides uncertainty estimates via multiagent consensus and scales with linear complexity to at least 10,000 polymers, enabling high-throughput screening at low computational cost. For a representative workload, the system completes inference in 16.3 s using about 2 GB of memory and 0.1 GPU hours, at an estimated cost of about $0.08. On a dedicated Tg benchmark, our approach attains R2 = 0.78, outperforming strong baselines including single-LLM prediction (R2 = 0.67), group-contribution methods (R2 = 0.71), and ChemCrow (R2 = 0.66). We further demonstrate metacognitive control in a polystyrene case study, where the system not only produces domain-level scientific outputs but continually monitors and optimizes its own behavior through tactical, strategic, and meta-strategic self-assessment.
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All authors Mahule Roy, Adib Bazgir, Arthur da Silva Sousa Santos, Yuwen Zhang

Materials Science · Cross-listed from physics.chem-ph

Advances in ion-doping of Ca-Mg silicate bioceramics for bone tissue engineering

Ashkan Namdar and Erfan Salahinejad

The use of bioceramics as hard tissue substitutes is extensive due to their excellent biocompatible and osteogenic behaviors. Among various bioceramics, Ca-Mg silicates are unique from the viewpoints of osteoinductive and mechanical properties, as well as their outstanding osteoconductive and angiogenic behaviors owing to the release of Si, Ca and Mg. Despite these distinct advantages, different compositions of these bioceramics still require mechanical and biological enhancements for further applications. For this purpose, doping with some ions like F-, Sr2+, Cu2+, Eu2+, Ba+, Ce3+ and some alkali cations has been proved to be a valued approach. This review attempts to bring together areas for the performance improvement of the further researched Ca-Mg silicates (i.e., diopside, akermanite, bredigite and monticellite) and the alteration of these compositions via ion-doping. It is concluded that a correct choice of dopants incorporated at the optimal concentration makes these silicates ideal bone substitutes competing or even superior to calcium phosphates (apatites) and bioglasses which are known as the most prominent bioceramics.
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Statistical Mechanics · Cross-listed from quant-ph

Impulsively Driven Fractional Relaxation: Exact Response, Scaling Laws, Frequency-Domain Signatures, and Memory-Induced Crossover Structures

Koichi Nakagawa

We investigate periodically impulsive fractional relaxation as a minimal model of nonlocal dissipative dynamics under repeated external stimulation. The free relaxation law is classical, but the driven problem introduces an additional timescale whose competition with the intrinsic fractional-memory scale generates nontrivial accumulation and crossover behavior. We derive the exact Laplace-domain and time-domain responses, establish the sparse-forcing scaling of the long-time averaged response, and obtain an analytical crossover interval proportional to the inverse fractional power of the relaxation coefficient. To separate established properties of Mittag–Leffler relaxation from the new effects of forcing, we explicitly compare the unforced, impulsive, and periodically driven settings. Extended long-time simulations verify the algebraic tail, while an independent L1 discretization provides a numerical benchmark for the exact solution. We further connect the relaxation kernel to measurable frequency-domain quantities through the Cole–Cole complex susceptibility and discuss interpretations in dielectric and viscoelastic relaxation, anomalous transport, non-Markovian open systems, and intermittent reinforcement. The resulting framework supplies an analytically solvable reference model for memory accumulation under repeated driving. The present analytical framework therefore provides a bridge between fractional relaxation theory and experimentally accessible time- and frequency-domain observables.
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Mesoscale and Nanoscale Physics

Hybridization of topologically distinct quartet modes in three-terminal graphene Josephson junctions

Asmaul Smitha Rashid, Le Yi, Takashi Taniguchi et al. (+4 more)

Multiterminal Josephson junctions offer a powerful playground for exploring exotic superconducting and topological phenomena beyond the reach of conventional two-terminal devices. In this work, we present the direct spectroscopic observation of Cooper quartet resonances, a signature of correlated tunneling of two Cooper pairs across the device, in a graphene three-terminal Josephson junction (3TJJ). Using tunneling spectroscopy, we visualize how Andreev bound states (ABS) evolve across a two-dimensional superconducting phase space, controlled by the two independent phase differences in the 3TJJ. These measurements reveal sharp local minima in the differential conductance spectra locked in a specific phase condition of superconducting phase variables. The resulting quantized trajectories around the compact torus of the superconducting phase variables reveal an underlying topological winding in the multipair transport. To interpret our results, we develop a theoretical model that connects the observed quartet resonances to the coherent hybridization of multiple ABS branches, a hallmark of the rich pairing process enabled by multiterminal geometries. Our results highlight the potential of multiterminal superconducting devices to host engineered superconducting states and pave the way for new approaches to topological band structure design based on phase-controlled, higher-order superconducting transport.
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All authors Asmaul Smitha Rashid, Le Yi, Takashi Taniguchi, Kenji Watanabe, Nitin Samarth, Régis Mélin, Morteza Kayyalha

Materials Science · Cross-listed from cs.LG

Multimodal Machine Learning for Soft High-k Elastomers under Data Scarcity

Brijesh FNU, Viet Thanh Duy Nguyen, Ashima Sharma et al. (+3 more)

Dielectric materials are critical building blocks for modern electronics such as sensors, actuators, and transistors. With rapid advances in soft and stretchable electronics for emerging human- and robot-interfacing applications, there is a growing need for high-performance dielectric elastomers. However, developing soft elastomers that simultaneously exhibit high dielectric constants (k) and low Young's moduli (E) remains a major challenge. Although individual elastomer designs have been reported, structured datasets that systematically integrate molecular sequence, dielectric, and mechanical properties are largely unavailable. To address this gap, we curate a compact, high-quality dataset of acrylate-based dielectric elastomers by aggregating experimental results from the past decade. Building on this dataset, we propose a multimodal learning framework leveraging large-scale pretrained polymer representations. These pretrained embeddings transfer chemical and structural knowledge from vast polymer corpora, enabling accurate few-shot prediction of dielectric and mechanical properties and accelerating data-efficient discovery of soft high-$k$ dielectric elastomers. Our data and implementation are publicly available at: https://github.com/HySonLab/Polymers
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All authors Brijesh FNU, Viet Thanh Duy Nguyen, Ashima Sharma, Md Harun Rashid Molla, Chengyi Xu, Truong-Son Hy

Soft Condensed Matter

Large temperature-up-jump simulations of a binary Lennard-Jones system

Aude Y. Amari, Lorenzo Costigliola and Jeppe C. Dyre

This paper presents simulations of the physical aging of a binary Kob-Andersen-type Lennard-Jones liquid following large temperature up-jumps from equilibrated states of high relaxation time. The purpose is to investigate how well the Tool-Narayanaswamy (TN) material-time concept works for this rather extreme case of aging. First the triangular relation of the potential energy is investigated. This is found to be well obeyed, making it possible to define a potential-energy-based material time $\xi$. We proceed to study aging toward equilibrium at the final temperature 0.48 for jumps from the two temperatures 0.43 and 0.37 (primarily), monitoring the following five quantities: the potential energy, the self-intermediate scattering function, the mean-square displacement, the dynamic susceptibility $\chi_4$, and the non-Gaussian parameter $\alpha_2$. The TN material-time prediction is that all time-autocorrelation functions should collapse to only depend on the material-time difference $\xi_2-\xi_1$. This is found to work better for the $0.43\to 0.48$ temperature jump than for the $0.37\to 0.48$ jump. Our findings thus confirm the general understanding that the TN aging formalism works best for systems that are never very far from equilibrium. This raises two questions for future work: Is the collapse significantly improved if each aging quantity is allowed its own material time? Can better collapse be obtained if the material-time is generalized to be locally defined (in order to reflect dynamic heterogeneity)?
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Materials Science

Crystal Representation in the Reciprocal Space

Osman Goni Ridwan, Hongfei Xue, Youxing Chen et al. (+2 more)

In crystallography, a structure is typically represented by the arrangement of atoms in the direct space. Furthermore, space group symmetry and Wyckoff site notations are applied to characterize crystal structures with only a few variables. While this representation is effective for data records and human learning, it lacks one-to-one correspondence between the crystal structure and its representation. This is problematic for many applications, such as crystal structure determination, comparison, and more recently, generative model learning. To address this issue, we propose to represent crystals in a four-dimensional (4D) reciprocal space featured by their Cartesian coordinates and scattering factors, which can naturally handle translation invariance and space group symmetry with the help of structure factors. In order to achieve rotational invariance, the 4D coordinates are then transformed into a power spectrum representation under the orthogonal spherical harmonic and radial basis. Hence, this representation captures both periodicity and symmetry of the crystal structure while also providing a continuous representation of the atomic positions and cell parameters in the direct space. Its effectiveness is demonstrated by applying it to several crystal structure matching and reconstruction tasks.
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All authors Osman Goni Ridwan, Hongfei Xue, Youxing Chen, Harish Cherukuri, Qiang Zhu

Quantum Gases

Quasicrystalline Analogue of the Haldane Model

Benedict Burgess and Nigel Cooper

We present a model for a topological quasicrystalline system which is suitable for realisation in cold-atom experiments. We define the model in terms of complex momentum-space couplings which break time-reversal symmetry (TRS), and detail how it may be experimentally realised using two-photon Raman couplings. In the weak-potential limit, we study the model analytically by calculating the bandstructure over a `quasi-Brillouin zone' (QBZ). We find symmetry-protected Dirac cones, which are gapped by a TRS-breaking term, resulting in a Chern number $\mathcal{C}=1$. This provides a direct analogy to the Haldane model, but now in a quasicrystalline setting. We also infer the number of states below the topological gap from the QBZ area. We verify our analysis with numerical calculations of periodic approximants to our system, constructing a phase diagram in parameter space which shows a topological region extending beyond the weak-potential regime. We also find examples of narrow Chern bands with the potential for hosting strongly-correlated physics. Our work raises questions about the nature of localisation and strongly-correlated states in Chern bands in quasiperiodic systems.
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Materials Science

Instability-driven mechanically locked states in functional oxide membranes

Varun Harbola, Thomas Emil le Cozannet, Denis Alikin et al. (+10 more)

Mechanical instabilities in thin solids offer a powerful route to engineer nonlinear responses, yet their controlled use in functional crystalline oxides has remained largely unexplored. Notably, by changing the aspect ratio of solids, the energy landscape around equilibrium can be modified to induce non-linearities under lateral stresses through non-lateral deformations. These nonlinear systems can develop multiple local energy minima where the system can settle and switch between states through the application of a driving force. Crucially, recent advances in oxide thin film growth have enabled the fabrication of freestanding oxide membranes, paving a viable path for their use in bistable architecture, particularly at the nanoscale. Here, we demonstrate that freestanding oxide membranes, such as SrTiO3 (STO) and BaTiO3 (BTO), relax into well-defined metastable buckling states when transferred onto lithographically defined cavities. The membrane deformation is determined by the interplay between built-in residual strain, bending stiffness, and cavity geometry, resulting in reproducible bistable states with distinct strain distributions. Using a combination of atomic force microscopy, in-contact Kelvin probe measurements, and finite-element modelling, we reveal that these mechanically locked states directly shape the electromechanical potential landscape of ferroelectric BaTiO3. We further demonstrate reversible snapthrough transitions between mechanically degenerate states, establishing complex oxides as deterministic, geometry-tunable building blocks for nonlinear nanoelectromechanical architectures. Our results illustrate a general strategy for exploiting mechanical instabilities to encode and manipulate functional responses in ultrathin crystalline membranes.
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All authors Varun Harbola, Thomas Emil le Cozannet, Denis Alikin, Shinhee Yun, Edwin Dollekamp, Andrea Roberto Insinga, Rasmus Bjørk, Nikolas Vitaliti, Thomas Sand Jespersen, Katja Isabelle Wurster, Dae-Sung Park, Jochen Mannhart, Nini Pryds

Superconductivity

Wave functions for the regular pentagonal two-dimensional quantum box and thin microstrip antenna

Tristan Langhorne, Erik E. Domenech, Juan Oliveros Gonzalez et al. (+1 more)

The general wave functions for the two-dimensional regular pentagonal quantum box and thin microstrip antenna are derived. As for the square, equilateral triangular, and circular disk-shaped boxes and antennas, there are two quantum nunbers $n$ and $m$. In those cases, $n\ge1 $ and $m\ge 0$ are both unlimited non-negative integers of any value. For the regular pentagon, only $n\ge1 $ is an unlimited positive quantum number, but $m_{\rm min}\le m\le 5$, where $m_{\rm min}=0$ for the pentagonal microstrip antenna with Neumann boundary conditions and $m_{\rm min}=1$ for the pentagonal quantum box with Dirichlet boundary conditions. Color-coded pictures of the wave functions for the regular pentagonal quantum box and microstrip antenna are presented for all allowed $m$ values and for $1\le n\le 2$ and for the microstrip antenna for all allowed $m$ values and $n=3$.
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All authors Tristan Langhorne, Erik E. Domenech, Juan Oliveros Gonzalez, Richard A. Klemm

Materials Science · Cross-listed from quant-ph

Colour Centre Formation in Silicon-On-Insulator for On-Chip Photonic Integration

Arnulf J. Snedker-Nielsen, David R. Gongora, Magnus L. Madsen et al. (+12 more)

Colour centres in silicon have great potential as single photon sources for quantum technologies. Some of them - like the T centre - also possess optically-active spins that enable spin-photon interfaces for generating entangled photons and multi-spin registers. This paper explores the generation of several types of colour centres in silicon for mass-manufacturable silicon-on-insulator quantum devices. We investigate how different processes in the device development affect the presence of the quantum emitters, including thermal annealing and fabrication steps for optical nanostructures. The study reveals coupled formation dynamics between different colour centres, identifies optimal parameters for annealing processes, and reports on the sensitivity to annealing duration and nanofabrication procedures for photonic integrated circuits. Furthermore, we discern stable optical signals from colour centres in silicon which have not been identified before.
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All authors Arnulf J. Snedker-Nielsen, David R. Gongora, Magnus L. Madsen, Christian H. Christiansen, Eike L. Piehorsch, Mathias Ø. Augustesen, Elvedin Memisevic, Sangeeth Kallatt, Rodrigo A. Thomas, Mark Kamper Svendsen, Peter Krogstrup Jeppesen, Marianne E. Bathen, Lasse Vines, Peter Granum, Stefano Paesani

Materials Science · Cross-listed from physics.optics

Experimental Realization of Optimized Ternary Mirror Coatings

V. Pierro, M. Granata, C. Michel et al. (+9 more)

We report on the first experimental realization of multi-material dielectric mirror coatings designed through a multi-objective optimization algorithm to simultaneously minimize thermal noise and optical losses. We validate this design strategy by fabricating and characterizing two distinct ternary systems: a SiNx -based proof-of-concept and a Ti:GeO2 -based system targeting lower optical losses. The performance of the SiN x coating shows remarkable agreement with predictions, demonstrating a noise amplitude spectral density reduction of 0.82 with respect to current reference coatings, and validating our design-to-fabrication pipeline. The Ti:GeO2 -based system achieves the crucial goal of sub-ppm absorption; its measured thermal noise, however, is higher than the theoretically predicted level of 0.71, extrapolated from single-layer material characterization. A dedicated tolerance analysis confirms that this discrepancy is not attributable to random thickness errors, emphasizing that further studies of the manufacturing process are needed to fully exploit this combination of materials. This work establishes a robust methodology for producing complex, high-performance optical coatings tailored for precision experiments.
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All authors V. Pierro, M. Granata, C. Michel, L. Pinard, B. Sassolas, D. Forest, N. Demos, S. Gras, M. Evans, I. M. Pinto, G. Avallone, V. Granata

Materials Science

An AI-ready fine-tuning framework for accurate machine-learning interatomic potentials in solid-solid battery interfaces

Xiaoqing Liu, Xinyu Yu, Yangshuai Wang et al. (+6 more)

Atomistic modeling of solid-solid battery interfaces is essential for understanding electro-chemo-mechanical coupling, but the complex interfacial chemistry and heterogeneous environments pose major challenges for quantum-accurate, data-efficient modeling. Herein, we propose an approach of fine-tuning with integrated replay and efficiency (FIRE), a general framework for universal machine-learning interatomic potentials by combining efficient configurational sampling with a replay-argumented continual strategy, achieving quantum-level accuracy at moderate cost. Across six solid-solid battery interface systems, FIRE consistently achieves root-mean-square errors in energy below 1 meV/atom and in force near 20 meV/angstrom, marking an order-of-magnitude improvement over existing models while requiring only 10% of the original datasets. In addition, the fine-tuned model successfully reproduces key mechanical and electrochemical properties of the materials, in close agreement with experimental data. The FIRE offers a generalizable and data-efficient approach for developing accurate interatomic potentials across diverse materials, enabling predictive simulations beyond the reach of first-principles methods.
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All authors Xiaoqing Liu, Xinyu Yu, Yangshuai Wang, Zhe-Tao Sun, Zedong Luo, Kehan Zeng, Teng Zhao, Shou-Hang Bo, Zhenli Xu

Mesoscale and Nanoscale Physics

Electrical and Thermal conductance through a Nodal Surface Semimetal-Insulator-Superconductor junction

Bhaskar Pandit, Debabrata Sinha and Satyaki Kar

Motivated by the unique dispersions close to the two dimensional band crossing in a topologically charged nodal surface semimetal (NSSM) spectrum, we perform theoretical analysis of quantum tunnelling through a junction consisting of such NSSM, an insulator and a s-wave superconductor (acronymed NSSM-I-SC junction). In particular, for excitation energies both more and less than the superconducting gap potential $\Delta$ we probe the normal and Andreev conductance for different incident orientations and thereby find the tunnelling electrical conductance through the heterostructure. The present work considers only the thin barrier limit which witness the conductance G to oscillate periodically with frequency $\pi$ as a function of the barrier strength, both in high and low doping limit. Such periodic behavior is also observed while calculating the thermal conductance $\kappa$ through the junction. Novelty of this problem is that the behavior of these G or $\kappa$ with insulator width are, in many respect, different compared to that from a normal metal - insulator - superconductor (NIS) junction on graphene or silicene. The findings can thus motivate experimentalists to culture renewed control over electric or thermal transport on topological materials.
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Materials Science

An autonomous living database for perovskite photovoltaics

Sherjeel Shabih, Hampus Näsström, Sharat Patil et al. (+16 more)

Scientific discovery is severely bottlenecked by the inability of manual curation to keep pace with exponential publication rates. This creates a widening knowledge gap. This is especially stark in photovoltaics, where the leading database for perovskite solar cells has been stagnant since 2021 despite massive ongoing research output. Here, we resolve this challenge by establishing an autonomous, self-updating living database (PERLA). Our pipeline integrates large language models with physics-aware validation to extract complex device data from the continuous literature stream, achieving human-level precision (>90%) and eliminating annotator variance. By employing this system on the previously inaccessible post-2021 literature, we uncover critical evolutionary trends hidden by data lag: the field has decisively shifted toward inverted architectures employing self-assembled monolayers and formamidinium-rich compositions, driving a clear trajectory of sustained voltage loss reduction. PERLA transforms static publications into dynamic knowledge resources that enable data-driven discovery to operate at the speed of publication.
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All authors Sherjeel Shabih, Hampus Näsström, Sharat Patil, Asmin Askin, Keely Dodd-Clements, Jessica Helisa Hautrive Rossato, Hugo Gajardoni de Lemos, Yuxin Liu, Florian Mathies, Natalia Maticiuc, Rico Meitzner, Edgar Nandayapa, Juan José Patiño López, Yaru Wang, Lauri Himanen, Eva Unger, T. Jesper Jacobsson, José A. Márquez, Kevin Maik Jablonka

Mesoscale and Nanoscale Physics

Tunable massive and acoustic plasmons in two-dimensional plasmonic crystals

I. V. Gorbenko, P. A. Gusikhin, V. Yu. Kachorovskii et al. (+1 more)

We theoretically investigate dispersion of plasma waves propagating in a lateral plasmonic crystal based on a two-dimensional electron system with grating gates. Two specific configurations are analyzed: a system with single grating gate having ungated gaps and a double-grating-gate system. We calculate the dispersion relations for the fundamental and several higher-order plasma modes, classifying them as either ${\it bright}$ or ${\it dark}$ excitations. At the boundaries of the Brillouin zones, the dispersion of both types of excitations is shown to be quadratic, justifying introduction of effective bright and dark plasmon masses. In the low-frequency limit, the plasmonic crystal spectrum exhibits an acoustic plasma mode characterized by a certain velocity. We demonstrate that the effective plasmon mass and acoustic velocity are highly sensitive to both the crystal geometry (specifically the lattice filling factor) and the gate voltages, enabling wide-range tunability.
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All authors I. V. Gorbenko, P. A. Gusikhin, V. Yu. Kachorovskii, V. M. Muravev

Mesoscale and Nanoscale Physics

Electric-current-assisted nucleation of zero-field hopfion rings

Xiaowen Chen, Dongsheng Song, Filipp N. Rybakov et al. (+9 more)

Magnetic hopfions are three-dimensional topological solitons – knotted, vortex-like spin configurations. In chiral magnets, hopfions can appear as isolated structures or they can be linked to skyrmion strings. Previous studies employed a sophisticated protocol and a special sample geometry to nucleate such hopfions linked to one or a few skyrmion strings. Here, we introduce an electric-current-assisted nucleation protocol that is simple and independent of the sample shape and size. The resulting hopfions exhibit extraordinary stability in the presence of both positive and negative magnetic fields, in perfect agreement with micromagnetic simulations. We also present a comprehensive framework for classifying hopfions, skyrmions, and merons by deriving the corresponding homotopy group.
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All authors Xiaowen Chen, Dongsheng Song, Filipp N. Rybakov, Nikolai S. Kiselev, Long Li, Wen Shi, Rui Wu, Xuewen Fu, Olle Eriksson, Stefan Bluegel, Haifeng Du, Fengshan Zheng

Materials Science

Scattering analysis of nano-scale chiral structures in optical vortex using Method of Moments

Chenxu Wang, Hideki Kawaguchi, Hiroaki Nakamura et al. (+2 more)

This paper presents a full 3D Method of Moments (MoM) simulation for analysis of scattering from nano-scale chiral ribbon structures under optical vortex illumination to aim to investigate electromagnetic mechanism of circular dichroism (CD) and optical vortex dichroism (VD). Both twist and helical nano-ribbons are modeled as dispersive materials scatterer. CD and VD are evaluated quantitatively by differences in scattering power. Numerical results demonstrate that angular momentum of optical light induces dichroic response effectively.
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All authors Chenxu Wang, Hideki Kawaguchi, Hiroaki Nakamura, Koichi Matsuo, Masahiro Katoh