CMP Journal 2025-07-28
Statistics
Nature Nanotechnology: 2
Nature Physics: 2
arXiv: 59
Nature Nanotechnology
Ultraclean monolayer amorphous carbon yields a high-precision proton beam
Original Paper | Synthesis of graphene | 2025-07-27 20:00 EDT
Huihui Lin, Jian Jiang, Yanxin Dou, Pin Lyu, Xiaocang Han, Yuan Meng, Yuanyuan He, Xin Zhou, Kangshu Li, Guoming Lin, Yu Teng, Jinxing Chen, Yang Meng, Thomas Osipowicz, Xiaoxu Zhao, Xiao Cheng Zeng, Jiong Lu
Ångström-scale polygonal rings in monolayer amorphous carbon (MAC) enhance its electronic and mechanical properties while providing unique ångström pores for precise subatomic species separation, essential for advancements in catalysis, energy and medicine. However, the absence of an industrial-scale synthesis method for intrinsic MAC has limited its technological applications compared with graphene and bulk amorphous materials. Herein, we report an industry-compatible disorder-to-disorder synthesis approach to achieve wafer-scale ultraclean MAC (UC-MAC) within a timescale of seconds, featuring optimized ångström polygons without detectable metal contamination, and nanosized pores. In contrast to metal-contaminated MAC, UC-MAC allows atomic-scale characterization of intrinsic electronic properties and functions as an ångström-scale membrane, facilitating the splitting of high-flux H2+ ions into a high-precision proton beam with minimal detrimental fragment-proton scattering events, about half and 40 times less than those from single-crystal graphene and commercial carbon thin films, respectively. The minimum possible membrane material thickness that can yield a highly sharpened proton beam with accurately modulated beam current is desired for proton therapy.
Synthesis of graphene, Two-dimensional materials
Ångström-resolution imaging of cell-surface glycans
Original Paper | Nanobiotechnology | 2025-07-27 20:00 EDT
Luciano A. Masullo, Karim Almahayni, Isabelle Pachmayr, Monique Honsa, Larissa Heinze, Sarah Fritsche, Heinrich Grabmayr, Ralf Jungmann, Leonhard Möckl
Glycobiology is rooted in the study of monosaccharides, ångström-sized molecules that are the building blocks of glycosylation. Glycosylated biomolecules form the glycocalyx, a dense coat encasing every human cell with central relevance–among others–in immunology, oncology and virology. To understand glycosylation function, visualizing its molecular structure is fundamental. However, the ability to visualize the molecular architecture of the glycocalyx has remained challenging. Techniques such as mass spectrometry, electron microscopy and fluorescence microscopy lack the necessary cellular context, specificity and resolution. Here we combine resolution enhancement by sequential imaging with metabolic labelling, enabling the visualization of individual sugars within glycans on the cell surface, thus obtaining images of the glycocalyx with a spatial resolution down to 9 Å in an optical microscope.
Nanobiotechnology, Nanophotonics and plasmonics, Super-resolution microscopy
Nature Physics
Capillary interactions drive the self-organization of bacterial colonies
Original Paper | Biological physics | 2025-07-27 20:00 EDT
Matthew E. Black, Chenyi Fei, Ricard Alert, Ned S. Wingreen, Joshua W. Shaevitz
Many bacteria inhabit thin water layers on solid surfaces. These thin films occur both naturally–in soils, on hosts and on textiles–and in the laboratory on agar hydrogels. In these environments, cells experience capillary forces, but it is unclear how these forces shape bacterial collective behaviour. Here we show that the water menisci formed around bacteria lead to capillary attraction between cells while still allowing them to slide past one another. We develop an experimental apparatus that allows us to control bacterial collective behaviour by varying the strength and range of capillary forces. Combining three-dimensional imaging and cell tracking with agent-based modelling, we demonstrate that capillary attraction organizes rod-shaped bacteria into densely packed nematic groups and influences their collective dynamics and morphologies. Our results suggest that capillary forces may be a ubiquitous physical ingredient in shaping microbial communities in partially hydrated environments.
Biological physics, Cellular motility, Microbiology
Predicting topological entanglement entropy in a Rydberg analogue simulator
Original Paper | Quantum simulation | 2025-07-27 20:00 EDT
Linda Mauron, Zakari Denis, Jannes Nys, Giuseppe Carleo
Predicting the dynamical properties of topological matter is a challenging task, not only in theoretical and experimental settings, but also computationally. Numerical studies are often constrained to studying simplified models and lattices. Here we propose a time-dependent correlated ansatz for the dynamical preparation of a quantum-spin-liquid state on a Rydberg atom simulator. Together with a time-dependent variational Monte Carlo technique, we can faithfully represent the state of the system throughout the entire dynamical preparation protocol. We are able to match not only the physically correct form of the Rydberg atom Hamiltonian but also the relevant lattice topology at system sizes that exceed current experimental capabilities. This approach gives access to global quantities such as the topological entanglement entropy, providing insight into the topological properties of the system. Our results confirm the topological properties of the state during the dynamical preparation protocol, and deepen our understanding of topological entanglement dynamics. We show that, while the simulated state exhibits local properties resembling those of a resonating-valence-bond state, in agreement with experimental observations, it lacks the latter’s characteristic topological entanglement entropy signature irrespective of the degree of adiabaticity of the protocol.
Quantum simulation, Topological defects
arXiv
Non-ideal subthreshold swing in aligned carbon nanotube transistors due to variable occupancy discrete charge traps
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-07-28 20:00 EDT
Saurabh S. Sawant, Teo Lara, Francois Leonard, Zhi Yao, Andrew Nonaka
Carbon nanotube transistors have been experimentally demonstrated to reach performance comparable and even surpassing that of silicon transistors. Further improvement requires addressing non-idealities arising from device fabrication that impact performance and reproducibility. One performance metric that determines energy efficiency is the subthreshold swing which is often observed to be 3-4 times larger than the ideal thermal limit. In this work, we present simulations indicating that a discrete number of variable occupancy hole trapping sites can explain the large subthreshold swing. Our simulations indicate that while three-dimensional trap distributions influence the subthreshold swing, only the traps in close proximity to the nanotubes have a significant impact. The results suggest that a density of trapping sites on the order of 0.5/nm$ ^2$ near the nanotubes is sufficient to significantly increase the subthreshold swing, requiring the removal or passivation of only a few sites per carbon nanotube.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
9 pages, 6 figures
Quantifying Coupled Dynamics in Phase-Space from State Distribution Snapshots
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-07-28 20:00 EDT
We quantify nonlinear interactions between coupled complex processes, when the system is subject to noise and not all its components are measurable. Our method is applicable even when the system cannot be continuously monitored over time, but is rather observed only in snapshots. Having only partial information about the local topology of the network and observations of relevant interacting variables is sufficient to translate qualitative knowledge of interactions into a quantitative characterization of the coupled dynamics. This approach turns a globally intractable problem into a sequence of solvable inference problems, to quantify complex interaction networks from incomplete snapshots of their statistical state.
Statistical Mechanics (cond-mat.stat-mech), Data Analysis, Statistics and Probability (physics.data-an)
Main text is 6.5 pages, Appendices 3.5 pages, 6 figures
Microscopic Fingerprint of Chiral Superconductivity
New Submission | Superconductivity (cond-mat.supr-con) | 2025-07-28 20:00 EDT
Xuefeng Wu, Xuan Hao, Zhuo Chen, Yuchang Cai, Minghao Wu, Congrun Chen, Kedong Wang, Fangfei Ming, Steven Johnston, Rui-Xing Zhang, Hanno H. Weitering
Chiral superconductors have long been theorized to break time-reversal symmetry and support exotic topological features such as Majorana modes and spontaneous edge currents, promising ingredients for quantum technologies. Although several unconventional superconductors may exhibit time-reversal symmetry breaking, clear microscopic evidence of chiral pairing has remained out of reach. In this work, we demonstrate direct real-space signatures of chiral superconductivity in a single atomic layer of tin on Si(111). Using quasiparticle interference imaging, we detected symmetry-locked nodal and antinodal points in the Bogoliubov quasiparticle wavefunction, tightly bound to atomic point defects in the tin lattice. These nodal features, along with their surrounding texture, form a distinct real-space pattern exhibiting a clear and exclusive hallmark of chiral superconductivity. Our findings, reinforced by analytical theory and numerical simulations, offer unambiguous evidence of chiral pairing in a two-dimensional material.
Superconductivity (cond-mat.supr-con), Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Materials Science (cond-mat.mtrl-sci), Strongly Correlated Electrons (cond-mat.str-el)
5 + 8 pages, 5 + 6 figures
Adaptive Neural Quantum States: A Recurrent Neural Network Perspective
New Submission | Disordered Systems and Neural Networks (cond-mat.dis-nn) | 2025-07-28 20:00 EDT
Jake McNaughton, Mohamed Hibat-Allah
Neural-network quantum states (NQS) are powerful neural-network ansätzes that have emerged as promising tools for studying quantum many-body physics through the lens of the variational principle. These architectures are known to be systematically improvable by increasing the number of parameters. Here we demonstrate an Adaptive scheme to optimize NQSs, through the example of recurrent neural networks (RNN), using a fraction of the computation cost while reducing training fluctuations and improving the quality of variational calculations targeting ground states of prototypical models in one- and two-spatial dimensions. This Adaptive technique reduces the computational cost through training small RNNs and reusing them to initialize larger RNNs. This work opens up the possibility for optimizing graphical processing unit (GPU) resources deployed in large-scale NQS simulations.
Disordered Systems and Neural Networks (cond-mat.dis-nn), Strongly Correlated Electrons (cond-mat.str-el), Machine Learning (cs.LG), Computational Physics (physics.comp-ph), Quantum Physics (quant-ph)
14 pages, 7 figures, 3 tables. Link to GitHub repository: this https URL
Strong enhancements to superconducting properties of 1D systems from metallic reservoirs
New Submission | Superconductivity (cond-mat.supr-con) | 2025-07-28 20:00 EDT
J. E. Ebot, Sam Mardazad, Lorenzo Pizzino, Johannes S. Hofmann, Thierry Giamarchi, Adrian Kantian
Using a 1D bilayer system comprised of pairing and metallic layers, the present work proves the striking power of reservoir-mediated boosting of superconductivity. Employing many-body numerics on large systems at zero and finite temperature, we unravel the complex processes by which the tuning of the metal parameters can impact the effective pairing strength as well as the long-range pair-pair-coupling mediated by the metal. It is these two processes that in turn can strongly enhance superconducting susceptibility and thermal superconducting correlation length over those of the isolated system. We show that in this way, even a 1D system can come very close to achieving superconducting long-range order.
Superconductivity (cond-mat.supr-con), Strongly Correlated Electrons (cond-mat.str-el)
6+4 pages, 3+5 figures
Propagating Neutral Modes in an Intervalley Coherent State
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-07-28 20:00 EDT
Richen Xiong, Yi Guo, Chenxin Qin, Fanzhao Yin, Taige Wang, Samuel L. Brantly, Junhang Qi, Jinfei Zhou, Zihan Zhang, Melike Erdi, Kenji Watanabe, Takashi Taniguchi, Shu Zhang, Seth Ariel Tongay, Andrea F. Young, Liang Fu, Chenhao Jin
The emergence of neutral collective modes is a hallmark of correlated quantum phases but is often challenging to probe experimentally. In two-dimensional flatband systems, charge responses have been intensively investigated, yet neutral excitations remain largely unexplored. In particular, intervalley coherent state (IVC) features a neutral Goldstone mode due to spontaneously broken valley U(1) symmetry. While IVC state has been proposed as a unifying theme across graphene- and semiconductor-based systems, its defining feature - the neutral Goldstone mode - remains elusive in experiment. Here we investigate space-and-time-resolved transport of neutral modes in twisted WSe2 moiré superlattices through a novel ultrafast imaging technique. We uncover two new propagating collective modes with very different velocities, which emerge near the van Hove singularity (VHS) in both intermediate- (3.54 degree) and large-angle (5 degree) twisted WSe2. The fast-propagating mode has a surprisingly large speed of ~3 km/s and is consistent with a Goldstone mode for an IVC state, while the slow-moving mode is likely a gapped amplitude mode. They can be understood as the spin-valley analogues of collective modes of a superfluid, whose propagation are imaged for the first time in a condensed matter system. Our study sets a new paradigm for probing charge-neutral modes in quantum materials and offers key insights into the interplay between charge and spin-valley physics in moiré superlattices.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Strongly Correlated Electrons (cond-mat.str-el), Quantum Physics (quant-ph)
Rubber Friction: Theory, Mechanisms, and Challenges
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-07-28 20:00 EDT
Rubber friction is of major practical importance in applications such as tires, rubber seals, and footwear. This review article focuses on the theory and experimental studies of rubber friction on substrates with random roughness. We examine both steady sliding and accelerated motion, with particular attention to the origins of the breakloose friction force and the influence of pre-slip, elasticity, and flash temperature on friction dynamics. We further discuss rolling friction for cylinders and spheres, as well as sliding friction for triangular sliders on dry and lubricated rubber surfaces. Theoretical predictions are compared with experimental results obtained using different materials, geometries, and environmental conditions, highlighting the importance of accounting for multiscale roughness. Open challenges, such as the role of adhesion enhancement, energy dissipation due to crack opening, and the physical origin of the short-distance roughness cut-off, are discussed.
Soft Condensed Matter (cond-mat.soft), Classical Physics (physics.class-ph)
Towards Accurate Thermal Property Predictions in Uranium Nitride using Machine Learning Interatomic Potential
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-28 20:00 EDT
Beihan Chen (1), Zilong Hua (2), Jennifer K. Watkins (2), Linu Malakkal (2), Marat Khafizov (3), David H. Hurley (2), Miaomiao Jin (1) ((1) Pennsylvania State University, (2) Idaho National Lab, (3) Ohio State University)
We present a combined computational and experimental investigation of the thermal properties of uranium nitride (UN), focusing on the development of a machine learning interatomic potential (MLIP) using the moment tensor potential (MTP) framework. The MLIP was trained on density functional theory (DFT) data and validated against various quantities including energies, forces, elastic constants, phonon dispersion, and defect formation energies, achieving excellent agreement with DFT calculations, prior experimental results and our thermal conductivity measurement. The potential was then employed in molecular dynamics (MD) simulations to predict key thermal properties such as melting point, thermal expansion, specific heat, and thermal conductivity. To further assess model accuracy, we fabricated a UN sample and performed new thermal conductivity measurements representative of single-crystal properties, which show strong agreement with the MLIP predictions. This work confirms the reliability and predictive capability of the developed potential for determining the thermal properties of UN.
Materials Science (cond-mat.mtrl-sci)
Defect Engineering the Interacting Many-body SSH Model
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-07-28 20:00 EDT
Lin Wang, Thomas Luu, Ulf-G. Meißner
The ability to engineer topologically distinct materials opens the possibility of enabling novel phenomena in low-dimensional nano-systems, as well as manufacturing novel quantum devices. One of the simplest examples, the SSH model with both even and odd number of sites, demonstrates the connection between localized edge states and the topology of the system. We show that the SSH model hosts localized spin centers due to the interplay between the localized edge states and the on-site Hubbard interaction. We further show how one can engineer any number of localized spin centers within the chain by careful addition of defects. These spin centers are paired in spin-singlet or spin-triplet channels within each block separated by the defects, and together they construct a chain of spin qubits. As this system is realizable experimentally, our findings provide a novel way for manipulating and engineering spin qubits in physical systems.
Strongly Correlated Electrons (cond-mat.str-el)
20 pages, 8 figures
Observation of Magnetic Devil’s Staircase-Like Behavior in Quasiperiodic Qubit Lattices
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-28 20:00 EDT
The devil’s staircase (DS) phenomenon is a fractal response of magnetization to external fields, traditionally observed in periodic ferromagnetic systems, where the commensurability between spin arrangements, lattice parameters, and external magnetic fields governs abrupt changes in magnetization. Its occurrence in aperiodic, fractal-type systems has remained largely unexplored, despite their natural compatibility with such phenomena. Using a quantum annealing device, we uncover a wealth of abrupt magnetic transitions between spin manifolds driven by increasing external magnetic fields within a simple yet effective Ising-model framework. In contrast to periodic systems, where DS arises from long-range competing interactions, our findings reveal that short-range, purely antiferromagnetic couplings in aperiodic geometries produce equally rich ground-state magnetization patterns. We demonstrate that while magnetic textures are determined by the lattice size, their formation remains remarkably robust and independent of scale, with commensurability emerging locally. Our results challenge the prevailing view that DS behavior is limited to periodic systems and establish quasiperiodic geometries as a natural host for this phenomenon.
Materials Science (cond-mat.mtrl-sci), Quantum Physics (quant-ph)
8 pages, 4 figures
Phys. Rev. B 112, 024435 - Published 24 July, 2025
Topological magneto-optics in the non-coplanar antiferromagnet Co_{1/3}NbS_2: Imaging and writing chiral magnetic domains
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-07-28 20:00 EDT
E. Kirstein, H. Park, I. Martin, J. F. Mitchell, N. Ghimire, S. A. Crooker
Despite its tiny net magnetization, the antiferromagnetic (AFM) van der Waals material Co$ _{1/3}$ NbS$ 2$ exhibits a large transverse Hall conductivity $ \sigma{xy}$ even at zero applied magnetic field, which arises, as recently shown, from the topological nature of its non-coplanar ``tetrahedral’’ AFM order. This triple-Q magnetic order can be regarded as the short-lengthscale limit of a magnetic skyrmion lattice, and has an intrinsic spin chirality. Here we show, using optical wavelengths spanning the ultraviolet to infrared (400-1000 nm), that magnetic circular dichroism (MCD) provides an incisive optical probe of the topological AFM order in Co$ _{1/3}$ NbS$ _2$ . Measurements as a continuous function of photon energy are directly compared with first-principles calculations, revealing the influence of the underlying quantum geometry on optical conductivity. Leveraging the power and flexibility of optical methods, we use scanning MCD microscopy to directly image chiral AFM domains, and demonstrate writing of chiral AFM domains.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Materials Science (cond-mat.mtrl-sci)
8 pages, 6 figures
X-ray Diffraction and Electrical Transport Imaging of Superconducting Superhydride (La,Y)H10
New Submission | Superconductivity (cond-mat.supr-con) | 2025-07-28 20:00 EDT
Abdul Haseeb Manayil Marathamkottil, Kui Wang, Nilesh P. Salke, Muhtar Ahart, Alexander C. Mark, Ross Hrubiak, Stella Chariton, Dean Smith, Vitali B. Prakapenka, Maddury Somayazulu, Nenad Velisavljevic, Russell J. Hemley
We report the synthesis and characterization of (La0.9Y0.1)H10 superhydrides exhibiting coexisting cubic Fm-3m and hexagonal P63/mmc clathrate phases observed over the pressure range from 168 GPa down to 136 GPa. Using synchrotron-based X-ray diffraction imaging (XDI) at the upgraded Advanced Photon Source (APS-U), we spatially resolved micron-scale distributions of these phases, revealing structural inhomogeneity across the sample. Four-probe DC resistance measurements confirmed superconductivity, with two distinct transitions: an onset at 244 K associated with the cubic phase and a second near 220 K linked to the hexagonal phase. Notably, resistance profiles collected from different current and voltage permutations showed variations in transition width and onset temperature that correlated with the spatial phase distribution mapped by XDI. These findings demonstrate a direct connection between local structural domains and superconducting behavior. Yttrium substitution is found to influence both the phase behavior and superconducting properties of LaH10-type clathrate hydrides. More broadly, this study highlights the utility of spatially correlating structural and electrical transport measurements in materials exhibiting heterogeneity under pressure, including hydride superconductors.
Superconductivity (cond-mat.supr-con)
X-ray Emission Spectropolarimetry of Strongly Anisotropic Single Crystal Systems using a Rowland Circle Geometry
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-07-28 20:00 EDT
Jared E. Abramson, Charles A. Cardot, Josh J. Kas, John J. Rehr, Werner Kaminsky, Herwig Michor, Marta Roman, Petra Becker, Gerald T. Seidler
Polarization dependence has historically seen extensive use in x-ray spectroscopy to determine magnetic and local geometric properties, but more broadly as a way to gain extra sensitivity to electronic structure at the level of individual magnetic orbitals. This is often done in the context of x-ray absorption through techniques like x-ray magnetic circular dichroism or x-ray linear dichroism, but it has seen little application to x-ray emission. Here we explore the information contained in the polarized emission of two 3d transition metal systems across both core-to-core (CtC) and valence-to-core emission (VtC) lines. We demonstrate how the Rowland circle geometry can be used as a spectropolarimeter, and apply it to the x-ray emission spectroscopy of spin-1/2 Cu(II) and spin-0 Ni(II) ions in LiVCuO4 and DyNiC2, respectively. From this we explore how the polarized XES interrogates of the occupied density of states at the valence level, either as a second order effect through Coulomb exchange (CtC x-ray emission) or by direct transitions (VtC x-ray emission). We find that the polarized x-ray emission can provide insights into the valence electron orbital occupation, in much the same way that is achievable with polarized absorption or angle-resolved photoemission spectroscopy techniques. Finally, we highlight how the individually polarized dipole emission spectra can be extracted from a linearly independent suite of directed emission spectra, allowing for polarized measurements at high Bragg angle with lower experimental broadening.
Strongly Correlated Electrons (cond-mat.str-el), Chemical Physics (physics.chem-ph)
Magnetic Field Induced Nonlinear Transport in LaTiO$_3$/SrTiO$_3$ Interfaces
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-07-28 20:00 EDT
Aidan Steineman, Maxim Khodas, Maxim Dzero
Motivated by the recent experimental measurements of the nonlinear longitudinal resistance of the spin-orbit coupled electron gas in the (111) LaTiO$ _3$ /SrTiO$ _3$ interfaces under external in-plane magnetic field [G. Tuvia \emph{et al.}, Phys. Rev. Lett. 132, 146301 (2024)], we formulate a theory of nonlinear electronic transport based on the analysis of the quantum kinetic equation for the Wigner distribution function. Specifically, we evaluate the magnetic field dependence of the second harmonic of the current density at arbitrary values of the magnetic field. The magnitude of the second harmonic increases linearly with the magnetic field at small fields. Upon further increase of the magnetic field, the second harmonic response reaches its maximum value. We find that the position of the peak and its width strongly depend on the relaxation rate due to disorder. Importantly, we discover that the direction of the nonlinear contribution to the current can be completely reversed when the magnetic field reaches a certain critical value.
Strongly Correlated Electrons (cond-mat.str-el), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
8 pages, 3 figures
Quantum diffusion in the Harper model under polychromatic time-perturbation
New Submission | Disordered Systems and Neural Networks (cond-mat.dis-nn) | 2025-07-28 20:00 EDT
Hiroaki S. Yamada, Kensuke S. Ikeda
Quantum dynamics of the Harper model with self-duality exhibits localized, diffusive, and ballistic states depending on the potential strength $ V$ . By adding time-dependent harmonic perturbations composed of $ M$ incommensurate frequencies, we show that all states of the Harper model transition to quantum diffusive states as the perturbation strength $ \epsilon$ increases for $ M \geq 3$ . The transition schemes and diffusion behaviors are discussed in detail and the phase diagram in the $ (\epsilon,V)$ parameter space is presented.
Disordered Systems and Neural Networks (cond-mat.dis-nn), Quantum Physics (quant-ph)
13 pages, 19 figures
Continuous and discontinuous shape transitions in the spatial distribution of self-propelling particles in power-law potential wells
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-07-28 20:00 EDT
Abhik Samui, Manoj Gopalakrishnan
We study the stationary states of an active Brownian particle and run-and-tumble particle in a two dimensional power-law potential well, in the limit where translational diffusion is negligible. The potential energy of the particle is taken to have the form $ U(r)\propto r^{n}$ , where $ n\geq 2$ and even. We derive an exact equation for the positional probability distribution $ \phi({\bf r})$ in two dimensions, and solve for the same, under the assumption that the particle’s orientation angle is a Gaussian variable. We show that $ \phi({\bf r})$ has compact support and undergoes a phase transition-like change in shape as the active velocity increases. For active Brownian particle, our theory predicts a continuous transition in shape for $ n=2$ and a discontinuous transition for $ n>2$ , both of which agree with simulation results. In the strongly active regime, the orientational probability distribution is unimodal near the outer boundary but becomes bimodal towards the interior, signifying orbiting motion. The unimodal-bimodal transition in the angular distribution is nearly absent for run-and-tumble particle.
Soft Condensed Matter (cond-mat.soft), Statistical Mechanics (cond-mat.stat-mech), Biological Physics (physics.bio-ph)
Prediction of Mechanical Properties and Thermodynamic Stability of Ti-N system using MTP Interatomic Potential
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-28 20:00 EDT
Pradeep Kumar Rana, Atharva Vyawahare, Rohit Batra, Satyesh Kumar Yadav
Ti-N material system have range of compounds with different stoichiometry like Ti2N, Ti3N2, Ti6N5, Ti4N3 alongwith Ti , TiN and solid solutions of N in Ti with a maximum of 23% solubility. In this work, we develop an interatomic potential based on moment tensor potential (MTP) that could reliably predict mechanical properties and thermodynamic stability of all Ti-N system. Taking into account the structural similarity and dissimilarity of various Ti-N system to choose training dataset was crucial for development of the potential. Root mean square error (RMSE) in prediction of formation energy using MTP potential compared to one calculated using density functional theory (DFT) for training dataset is 2.1 meV/atom and for testing dataset is 6.8 meV/atom. The frequency of absolute error in formation energy peaks at a maximum value of 3.8 meV/atom for system that was part of training dataset, while it peaks at 7.6 meV/atom for systems that are not part of the training dataset. Furthermore, the distribution and variability of elastic constants across compositions are systematically evaluated, revealing trends consistent with DFT benchmarks. The developed potential was used to predict energy of new phases in Ti-N system. We show that structures with N/Ti ratios ranging from 0 to 1 can be thermodynamically stable. A maximum deviation of 10 meV/atom from the convex hull plot of formation energy 0K was observed for a few system.
Materials Science (cond-mat.mtrl-sci)
Spinon Singlet: Microscopic Mechanism of $d$-Wave Pairing in a Partially-Filled Stripe
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-07-28 20:00 EDT
Jia-Long Wang, Shi-Jie Hu, Xue-Feng Zhang
Significant research advances have led to a consensus that the Fermi-Hubbard model and its extended variants are archetypal frameworks for elucidating the intertwined relationship between stripe orders and superconductivity in hole-doped high-$ T_c$ materials. Notably, the Hubbard quantum simulator has recently achieved several remarkable breakthroughs, e.g., being successfully cooled down to the cryogenic regime and enabling the observation of stable fluctuating stripes. However, the microscopic mechanism behind $ d$ -wave pairing of electrons in the presence of stripes at low temperatures remains poorly understood due to the intricate interplay among the strongly correlated effects and non-negligible thermal fluctuations. Here, we conduct a close investigation of a partially-filled stripe in the representative $ t$ -$ J$ and Fermi-Hubbard models with both numerical and analytical methods. Analogous to quantum gas microscopy, the perfect sampling technique allows us to obtain the high-confidence statistics of the Fock basis states appearing in the ground-state wavefunction. In a refreshing physical paradigm, these data demonstrate that two spinons with opposite chiralities tend to spontaneously pair into a singlet state, which naturally gives rise to the $ d$ -wave pairing pattern. Then, using the effective theory of quantum colored string, we reconstruct the wavefunction and determine the nature of spinon pairing and its connection to the $ d$ -wave pairing pattern. Furthermore, spinon singlet pairs enable the establishment of a long-range pair-pair correlation between double stripes. Our work offers new insights into the role of stripe orders in mediating $ d$ -wave superconductivity and paves the way for further exploration of multi-stripe-mediated pairing mechanisms in the Fermi-Hubbard model.
Strongly Correlated Electrons (cond-mat.str-el), Quantum Gases (cond-mat.quant-gas), Quantum Physics (quant-ph)
5 pages, 5 figures, comments are welcome and more information at this http URL
Antibonding and Electronic Instabilities in GdRu2X2 (X = Si, Ge, Sn): A New Pathway Toward Developing Centrosymmetric Skyrmion Materials
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-07-28 20:00 EDT
Dasuni N. Rathnaweera, Xudong Huai, K. Ramesh Kumar, Sumanta Tewari, Michał J. Winiarski, Richard Dronskowski, Thao T. Tran
Chemical bonding is key to unlocking the potential of magnetic materials for future information technology. Magnetic skyrmions are topologically protected nano-sized spin textures that can enable high-density low-power spin-based electronics. Despite increasing interest in the discovery of new skyrmion hosts and their characterization, the electronic origins of the skyrmion formation remain unknown. Here, we study GdRu2X2 (X = Si, Ge, Sn) as a model system to study the connection among chemical bonding, electronic instability, and the critical temperature and magnetic field at which skyrmions evolve. The nature of the electronic structure of GdRu2X2 is characterized by chemical bonding, Fermi surface analysis, and density of energy function. As X-p orbitals become more extended from Si-3p to Ge-4p and Sn-5p, improved interactions between the Gd spins and the [Ru2X2] conduction layer and increased destabilizing energy contributions are obtained. GdRu2Si2 possesses a Fermi surface nesting (FSN) vector [Q = (q, 0, 0)], whereas GdRu2Ge2 displays two inequivalent FSN vectors [Q = (q, 0, 0); QA = (q, q, 0)] and GdRu2Sn2 features multiple Q vectors. In addition, competing ferromagnetic and antiferromagnetic exchange interactions in the Gd plane become more pronounced as a function of X. These results reveal some correlation among the electronic instability, the competing interaction strength, and the temperature and magnetic field conditions at which the skyrmions emerge. This work demonstrates how chemical bonding and electronic structure enable a new framework for understanding and developing skyrmions under desired conditions that would otherwise be impossible.
Strongly Correlated Electrons (cond-mat.str-el), Materials Science (cond-mat.mtrl-sci)
Atomic-Scale Heterogeneity of Hydrogen in Metal Hydrides Revealed by Electron Ptychography
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-28 20:00 EDT
Pengcheng Li, Chenglin Pua, Zehao Dong, Zhengxiong Su, Tao Liu, Chao Cai, Huahai Shen, Lin Gu, Zhen Chen
Hydrogen plays critical roles in materials science, particularly for advancing technologies in hydrogen storage and phase manipulation, while also posing challenges like hydrogen embrittlement. Understanding its behavior, vital for improving material properties, requires precise determination of atomic-scale distribution-a persistent challenge due to hydrogen’s weak electron scattering and high mobility, as well as the limitations of conventional transmission electron microscopy. We demonstrate that multislice electron ptychography (MEP) overcomes these constraints through three key advances: exceptional sensitivity for hydrogen occupancy, three-dimensional quantification, and picometer-level precision in atomic positioning. Experimentally, MEP resolves heterogeneous hydrogen distributions and quantifies hydrogen-induced lattice displacements with picometer precision in multi-principal-element alloy hydrides. This work demonstrates MEP as a transformative method for directly probing hydrogen atoms in solids, unlocking fundamental understanding of hydrogen’s impact on material properties.
Materials Science (cond-mat.mtrl-sci), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
32 pages, 4 main figures, and 13 SI figures
Pressure-mediated crystalline g-C3N4 with enhanced spatial charge transport for solar H2 evolution and photocathodic protection of 304 stainless steels
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-28 20:00 EDT
Xiaochun Gao, Shaoqi Hou, Dawei Su
Conjugated polymeric g-C3N4 has emerged as a leading semiconductor for solar-to-chemical energy conversion due to its unique electronic band structure, robust physicochemical stability, and environmental benignity. However, defect engineering-while effective at enhancing visible-light absorption and charge separation-often introduces excessive dangling bonds and lattice disorder, which exacerbate carrier recombination and impair light harvesting. High crystallinity offers a complementary route to improve spatial charge transport, yet strategies that concurrently optimize crystallinity and surface defects remain underexplored. Here we report a pressure-mediated ion thermal synthesis of high-crystalline g-C3N4 (CCN-P) using a NaCl/KCl eutectic salt under elevated pressure. The molten salt facilitates in-plane and cross-plane crystal growth, while applied pressure reduces interlayer spacing and shortens photocarrier pathways. This dual modulation yields CCN-P with balanced surface defects (-CN and -NHx), an electron-trapping resistance (Rtrap) of 11.36 k{\Omega} cm2 and a photocarrier decay rate constant of 0.013 s-1. CCN-P achieves a hydrogen evolution rate of 2168.8 {\mu}mol g-1 h-1 and delivers 78.5% dark photocathodic protection of 304 stainless steel over 7500 s, outperforming bulk and conventionally crystalline g-C3N4. This straightforward pressure-ion thermal approach provides a versatile platform for tailoring crystalline frameworks and defect distributions in polymeric semiconductors for efficient solar energy conversion.
Materials Science (cond-mat.mtrl-sci)
Real-space second Chern number using the kernel polynomial method
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-07-28 20:00 EDT
We evaluate the real-space second Chern number of four-dimensional Chern insulators using the kernel polynomial method. Our calculations are performed on a four-dimensional system with $ 30^4$ sites, and the numerical results agree well with theoretical expectations. Moreover, we show that the method is capable of capturing the disorder effects. This is evidenced by the phase diagram obtained for disordered systems, which agrees well with predictions from the self-consistent Born approximation. Furthermore, we extend the method to six dimensions and perform an exploratory real-space calculation of the third Chern number. Although finite-size effects prevent full quantization, the numerical results show qualitative agreement with theoretical expectations. The study represents a step forward in the real-space characterization of higher-dimensional topological phases.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Atomic-scale confinement of strongly charged 180 degree domain wall pairs in ZrO2
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-28 20:00 EDT
Nashrah Afroze, Hamoon Fahrvandi, Guodong Ren, Pawan Kumar, Christopher Nelson, Sarah Lombardo, Mengkun Tian, Ping-Che Lee, Jiayi Chen, Manifa Noor, Kisung Chae, Sanghyun Kang, Prasanna Venkat Ravindran, Matthew Bergschneider, Gwan Yeong Jung, Pravan Omprakash, Gardy K. Ligonde, Nujhat Tasneem, Dina Triyoso, Steven Consiglio, Kanda Tapily, Robert Clark, Gert Leusink, Jayakanth Ravichandran, Shimeng Yu, Andrew Lupini, Andrew Kummel, Kyeongjae Cho, Duk-Hyun Choe, Nazanin Bassiri-Gharb, Josh Kacher, Rohan Mishra, Jun Hee Lee, Asif Khan
Self organized polar textures can occur in ferroelectric materials across multiple length scales, from nanometer scale vortices and skyrmions, to mesoscopic stripe domains, and macroscopic twin patterns, making these phenomena central to condensed matter physics and nanotechnology. Silicon compatible ferroelectrics such as HfO2 and ZrO2 spontaneously form alternating stacks of two dimensional (2D) polar and nonpolar half unit cell layers, effectively confining dipoles to isolated, single atomic plane layers. However, the arrangement of dipoles within each polar plane is generally considered uniform. Here, by utilizing scanning transmission electron microscopy (STEM) of an ultrathin ZrO2 film in the plan view orientation, we show that within these irreducibly narrow polar layers, the dipole organization can be strikingly non-uniform, forming atomically thin, dimensionally confined, charged 180 degree domain walls, at most a few unit cells long, alternating between head to head and tail to tail configurations. Head to head and tail to tail walls each adopt completely distinctive interfacial structures and confine the in-plane domains to a sub nm2 footprint, making them one of the smallest domains to be reported in any polar material. This work represents the first experimental observation of antipolar ferroic ordering via strongly charged domain walls, while being nested within the self organized polar nonpolar layering, revealing a novel hierarchical self-organization of polar textures at the atomic scale, and opening new pathways to atomically dense memories and domain wall nanoelectronics in silicon compatible, simple binary oxides.
Materials Science (cond-mat.mtrl-sci)
4 main figures, 10 supplementary figures
Stoichiometric and Non-stoichiometric Cesium Potassium Antimonide Photocathodes: Ab-initio Insights into its Properties for Photoemission
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-28 20:00 EDT
Sandip Aryal, Gaoxue Wang, Enrique R. Batista
Alkali-metal antimonides, especially cesium-potassium-antimonide (CsK2Sb), are strong candidates for next-generation photocathodes in linear accelerators due to their low work-function, fast response, high quantum yield, and ability to operate under visible light. In this study, first-principles methods are used to examine the structural, electronic, optical, and surface properties of CsK2Sb relevant to its photoemission performance. Our results for CsK2Sb show strong absorption in the visible range consistent with experimental observations. The computed work-functions for the stable surfaces are significantly lower than the commonly used metallic photocathodes. This material exhibits electron and hole mobilities of 111.86 cm2/Vs and 3.24 cm2/Vs, respectively. Since real materials inherently contain intrinsic defects, we analyze native point defects in CsK2Sb and identified Cs and K vacancies as most likely. These defects introduce mid-gap states, modify the absorption spectrum, and may significantly influence photoemission behavior. This work provides valuable insights into optimizing CsK2Sb for high-efficiency photocathode applications.
Materials Science (cond-mat.mtrl-sci)
Accuracy and Limitations of Machine-Learned Interatomic Potentials for Magnetic Systems: A Case Study on Fe-Cr-C
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-28 20:00 EDT
E.O. Khazieva, N.M. Chtchelkatchev, R.E. Ryltsev
Machine-learned interatomic potentials (MLIPs) have become the gold standard for atomistic simulations, yet their extension to magnetic materials remains challenging because spin fluctuations must be captured either explicitly or implicitly. We address this problem for the technologically vital Fe-Cr-C system by constructing two deep machine learning potentials in DeePMD realization: one trained on non-magnetic DFT data (DP-NM) and one on spin-polarised DFT data (DP-M). Extensive validation against experiments reveals a striking dichotomy. The dynamic, collective properties, viscosity and melting temperatures are reproduced accurately by DP-NM but are incorrectly estimated by DP-M. Static, local properties, density, and lattice parameters are captured excellently by DP-M, especially in Fe-rich alloys, whereas DP-NM fails. This behaviour is explained by general properties of paramagnetic state: at high temperature, local magnetic moments self-average in space and time, so their explicit treatment is unnecessary for transport properties but essential for equilibrium volumes. Exploiting this insight, we show that a transfer-learning protocol, pre-training on non-magnetic DFT and fine-tuning on a small set of spin-polarised data, reduces the computational cost to develop magnetic MLIPs by more than an order of magnitude. Developing general-purpose potentials that capture static and dynamic behaviors throughout the whole composition space requires proper accounting for temperature-induced spin fluctuations in DFT calculations and correctly incorporating spin degrees of freedom into classical force fields.
Materials Science (cond-mat.mtrl-sci), Chemical Physics (physics.chem-ph), Computational Physics (physics.comp-ph)
9 pages, 9 figures
Kibble-Zurek mechanism for dissipative discrete time crystals
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-07-28 20:00 EDT
Roy D. Jara Jr., Jayson G. Cosme
We demonstrate that the Kibble-Zurek mechanism (KZM) holds for open systems transitioning from a disordered phase to a discrete time crystal (DTC). Specifically, we observe the main signatures of the KZM when the system is quenched into a DTC, which are the characteristic power-law scaling with quench time of the number of spatial defects and the transition delay measured from the time at which the system crosses the critical point. We show analytically that this universal behavior can be traced back to how systems that can be mapped onto a dissipative linear parametric oscillator (DLPO) satisfy the adiabatic-impulse (AI) approximation, evinced by the divergence of the relaxation time of the DLPO near a critical point. We verify our predictions in both the classical and quantum regimes by considering two systems: the Sine-Gordon model, which is a paradigmatic system for emulating classical DTCs; and the open Dicke lattice model, an array of spin-boson systems subjected to quantum fluctuations. For both systems, the DTCs can be tuned from a ferromagnetic to an antiferromagnetic order by varying the driving frequency, thus allowing us to test the validity of KZM for arbitrary spatiotemporal ordering.
Statistical Mechanics (cond-mat.stat-mech), Quantum Gases (cond-mat.quant-gas), Pattern Formation and Solitons (nlin.PS), Quantum Physics (quant-ph)
All-Dry Transfer of Graphene Film by Van der Waals Interactions
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-28 20:00 EDT
Seong-Jun Yang, Shinyoung Choi, Francis Okello Odongo Ngome, Ki-Jeong Kim, Si-Young Choi, Cheol-Joo Kim
We report a method that uses van der Waals interactions to transfer continuous, high-quality graphene films from Ge(110) to a different substrate held by hexagonal boron nitride carriers in a clean, dry environment. The transferred films are uniform and continuous with low defect density and few charge puddles. The transfer is effective because of the weak interfacial adhesion energy between graphene and Ge. Based on the minimum strain energy required for the isolation of film, the upper limit of the interfacial adhesion energy is estimated to be 23 meV per carbon atom, which makes graphene/Ge(110) the first as-grown graphene film that has an substrate adhesion energy lower than typical van der Waals interactions between layered materials. Our results suggest that graphene on Ge can serve as an ideal material platform to be integrated with other material systems by a clean assembly process.
Materials Science (cond-mat.mtrl-sci)
35 pages, 18 figures
Nano Letters 19 (2019) 3590-3596
Step-directed Epitaxy of Uni-directional Hexagonal Boron Nitride on Vicinal Ge(110)
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-28 20:00 EDT
Ju-Hyun Jung, Chao Zhao, Seong-Jun Yang, Jun-Ho Park, Woo-Ju Lee, Su-Beom Song, Jonghwan Kim, Chan-Cuk Hwang, Seung-Hwa Baek, Feng Ding, Cheol-Joo Kim
Insulating hexagonal boron nitride (hBN) films with precisely controlled thickness are ideal dielectric components to modulate various interfaces in electronic devices. To achieve this, high-quality hBN with controlled atomic configurations must be able to form pristine interfaces with various materials in devices. However, previously reported large-scale hBN films with uniform thickness either are polycrystalline or are not suitable for atomically clean assembly via mechanical exfoliation, limiting their applications in device technology. Here, we report the large-scale growth of monolayer single crystalline hBN films on Ge(110) substrates by using chemical vapor deposition (CVD). Vicinal Ge(110) substrates are used for the step-directed epitaxial growth of hBN, where Ge atomic steps act as the hBN nucleation sites, guiding the uni-directional alignments of multiple hBN domains. Density functional theory (DFT) calculations reveal that the optimum hydrogen passivations on both hBN edges and Ge surfaces enable the epitaxial coupling between hBN and the Ge step edges and the single crystallinity of the final hBN films. Using epitaxially grown monolayer hBN films, we fabricate a few hBN films with controlled stacking orders and pristine interfaces through a layer-by-layer assembly process. These films function as high-quality dielectrics to enhance carrier transport in graphene and MoS2 channels.
Materials Science (cond-mat.mtrl-sci)
38 pages,16 figures
Small Structures 5 (2024) 2400297
Phases of a Bose-Einstein condensate of microwave-shielded dipolar molecules
New Submission | Quantum Gases (cond-mat.quant-gas) | 2025-07-28 20:00 EDT
Chiara J. Polterauer, Robert E. Zillich
Bose-Einstein condensation of dipolar molecules can be achieved by shielding loss channels with microwave fields. The microwave coupling can be approximated by effective dipole-dipole interactions with a short-range repulsion. We study properties and stability of these molecular Bose gases with a many-body variational method, the hypernetted-chain Euler-Lagrange method for a wide range of densities and repulsion strengths of the microwave shield. We find a homogeneous gas-like phase which, however, is unstable at low density against density waves: at a critical density, which depends on the repulsion strength, the dipolar fluid undergoes a phase transition to a layer phase. Thus, if the molecular condensate is expanded adiabatically by decreasing the confinement strength, it will spontaneously form layers at the critical density. These quasi-two-dimensional layers can be self-bound, hence form two-dimensional liquids. By varying the microwave shield, the predicted equilibrium densities span more than an order of magnitude.
Quantum Gases (cond-mat.quant-gas)
11 pages, 9 figures
A Riemann-Hilbert Approach to Slavnov Overlaps in the Lieb-Liniger model
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-07-28 20:00 EDT
We provide a method to compute Slavnov overlaps in the Lieb-Liniger model using the steepest descent method of the Riemann-Hilbert problem. To do so, we employ the Matsuo-Kostov Representation of the Slavnov overlaps to write an integral equation for the respective resolvent, and then represent this equation as a Riemann-Hilbert problem. To demonstrate the validity and applicability of the method by computing the Anderson orthogonality catastrophe in the $ c\to\infty$ limit, corresponding to free-fermion.
Strongly Correlated Electrons (cond-mat.str-el), Mathematical Physics (math-ph)
Multifractality and statistical localization in the sparse Barrat-Mézard trap model
New Submission | Disordered Systems and Neural Networks (cond-mat.dis-nn) | 2025-07-28 20:00 EDT
We study within a paradigmatic model for glassy dynamics, the Barrat-Mézard trap model, the effect of a nontrivial network structure in the connectivity among traps. Sparseness of this network has recently been shown to lead to divergences in the bulk of the spectrum of the associated master operator [1, 2]. We analyse here specifically the properties of the relaxation modes that contribute to these spectral divergences. We characterize the statistics of the corresponding wavefunctions and demonstrate that they are localized with multifractal properties. The localization patterns are unrelated to the spatial (network) topology, however, and instead fall within the recently introduced class of statistical localization phenomena [3]. To rationalize these results we develop an effective model that successfully explains both the spectral divergences and the power law tails in the wavefunction entries, and provides a clear physical picture of why the localization is statistical rather than spatial.
Disordered Systems and Neural Networks (cond-mat.dis-nn)
13 pages, 10 figures
Highly efficient coherent amplification of zero-field spin waves in YIG nano-waveguides
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-07-28 20:00 EDT
K. O. Nikolaev, S. R. Lake, B. Das Mohapatra, G. Schmidt, S. O. Demokritov, V. E. Demidov
Transmission and processing of information at the nanoscale using spin waves and their quanta - magnons, offers numerous advantages and opportunities that make it a promising next-generation technology for integrated electronics. The main challenges that still need to be addressed to ensure high competitiveness of magnonic devices include finding ways to efficiently amplify spin waves in nanostructures and developing nanocircuits that can operate without the need for an external bias magnetic field. Here we demonstrate how these two challenges can be solved using nano-waveguides fabricated from a low-loss magnetic insulator. We show that by using local parametric pumping with a power of only a few milliwatts, one can achieve coherent amplification of spin-wave pulses by more than two orders of magnitude at zero bias magnetic field. Our results provide a simple solution to problems that have long prevented the implementation of efficient integrated magnonic circuits.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Applied Physics (physics.app-ph)
Sensing magnonic quantum superpositions using a bosonic mode as the probe
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-07-28 20:00 EDT
Bashab Dey, Sonu Verma, Mathias Weiler, Akashdeep Kamra
Sensing quantum superpositions of a magnonic mode has been accomplished using a superconducting qubit by realizing an effective dispersive interaction between the two systems. Here, we theoretically demonstrate that a seemingly classical bosonic mode can be utilized as a probe for sensing quantum superpositions of a magnon mode, while outperforming a qubit in various regards as the sensor. Considering another magnon mode in an antiferromagnet as the probe mode, we delineate the required dispersive coupling emerging directly from antiferromagnetic exchange interaction. When a phonon is used as the probe mode, we derive the effective dispersive coupling emerging from the lowest-order nonlinear magnon-phonon interactions. Our two considered examples provide the general design principles for identifying and utilizing a bosonic probe mode for sensing quantum superpositions in a physical platform of interest.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Entanglement across scales: Quantics tensor trains as a natural framework for renormalization
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-07-28 20:00 EDT
Stefan Rohshap, Jheng-Wei Li, Alena Lorenz, Serap Hasil, Karsten Held, Anna Kauch, Markus Wallerberger
Understanding entanglement remains one of the most intriguing problems in physics. While particle and site entanglement have been studied extensively, the investigation of length or energy scale entanglement, quantifying the information exchange between different length scales, has received far less attention. Here, we identify the quantics tensor train (QTT) technique, a matrix product state-inspired approach for overcoming computational bottlenecks in resource-intensive numerical calculations, as a renormalization group method by analytically expressing an exact cyclic reduction-based real-space renormalization scheme in QTT language, which serves as a natural formalism for the method. In doing so, we precisely match the QTT bond dimension, a measure of length scale entanglement, to the number of rescaled couplings generated in each coarse-graining renormalization step. While QTTs have so far been applied almost exclusively to numerical problems in physics, our analytical calculations demonstrate that they are also powerful tools for mitigating computational costs in semi-analytical treatments. We present our results for the one-dimensional tight-binding model with n-th-nearest-neighbor hopping, where the 2n rescaled couplings generated in the renormalization procedure precisely match the QTT bond dimension of the one-particle Green’s function.
Strongly Correlated Electrons (cond-mat.str-el), Mathematical Physics (math-ph), Computational Physics (physics.comp-ph)
30 pages (16 pages without appendix), 12 figures
Magnetoelectric coupling and its impact on the multicaloric effect
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-28 20:00 EDT
Kentaro Ino, Keisuke Matsuura, Tetsuya Nomoto, Takashi Kurumaji, Yoshinori Tokura, Fumitaka Kagawa
The multicaloric effect, which represents the reversible entropy change that occurs when both external magnetic and electric fields are applied, is an interesting phenomenon characteristic to multiferroics. Targeting the multicaloric effect in the typical multiferroic (Fe$ _{0.95}$ Zn$ _{0.05}$ )$ _2$ Mo$ _3$ O$ _8$ , we experimentally evaluate the isothermal entropy change due to a magnetoelectric cross-correlation. A pronounced cross-correlation-derived isothermal entropy change is found at the magnetic ordering temperature. By exploring the literature, we suggest that a magnetic phase transition may tend to involve a considerably larger cross-correlation-derived entropy change than that derived from the linear magnetoelectric effect.
Materials Science (cond-mat.mtrl-sci), Strongly Correlated Electrons (cond-mat.str-el)
34 pages, 10 figures
Phys. Rev. B 112, 024434 (2025)
The Josephson effect in Fibonacci superconductors
New Submission | Superconductivity (cond-mat.supr-con) | 2025-07-28 20:00 EDT
Ignacio Sardinero, Jorge Cayao, Keiji Yada, Yukio Tanaka, Pablo Burset
We theoretically investigate the Josephson effect between two proximized Fibonacci quasicrystals. A quasiperiodic modulation of the chemical potential on a superconducting substrate induces topological gaps and edge modes with energies above the superconducting gap. We reveal that these edge modes develop superconducting correlations which significantly impact the Josephson current, and we term them Fibonacci-Andreev bound states. Notably, the contribution from these edge modes can be controlled by the Fibonacci sequence arrangement, known as phason angle, and can dominate the Josephson effect over the conventional subgap Andreev bound states in short junctions. The interplay between the Josephson effect and nontrivial edge modes in quasiperiodic systems presents new opportunities for exploring exotic superconducting phenomena in quasicrystals.
Superconductivity (cond-mat.supr-con), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
14 pages, 10 figures
$1/f^{3/2}$ Power Spectrum at the Phonon Bottleneck
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-07-28 20:00 EDT
The common observation of a `$ 1/f^\alpha$ ‘ power spectrum with $ \alpha<2$ constitutes one of the enduring mysteries of condensed matter physics. Here it is shown that a $ 1/f^{\alpha}$ power spectrum, with $ \alpha = 3/2$ , can arise when an ensemble of two–level systems is coupled to a heat bath by means of a system of Bosonic quasiparticles. The model considered is the classic model of Faughnan and Strandberg of the phonon bottleneck, and the anomalous relaxation is associated with an approximate non-equilibrium steady state of the phonons maintained by slow spin relaxation. It is shown that a frequency-dependent susceptibility can be defined in the steady state and that the prediction $ \alpha=3/2$ , or the equivalent stretched exponential relaxation with exponent $ \beta = 2-\alpha = 1/2$ , is consistent with existing experimental data. These results give an insight into the origins of anomalous relaxation in condensed matter and the practical behaviour of two-level systems.
Statistical Mechanics (cond-mat.stat-mech)
5 pages, 5 figures
Phase transitions in voting simulated by an intelligent Ising model
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-07-28 20:00 EDT
Guanyu Xu, Jiahang Chen, Xin Zhou, Yanting Wang
Voting is an important social activity for expressing public opinions. By conceptually considering a group of voting agents to be intelligent matter, the impact of real-time information on voting results is quantitatively studied by an intelligent Ising model, which is formed by adding nonlinear instantaneous feedback of the overall magnetization to the conventional Ising model. In the new model, the interaction strength becomes a variable depending on the total magnetization rather than a constant, which mimics the scenario that the decision of an individual during vote influenced by the dynamically changing polling result during the election process. Our analytical derivations along with Mote Carlo simulations reveal that, with a positive feedback, the intelligent Ising model exhibits phase transitions at any finite temperatures, a feature lacked in the conventional one-dimensional Ising model. In all dimensions, by varying the feedback strength, the system changes from going through a second-order phase transition to going through a first-order phase transition with increasing temperature, and the two types of phase transitions are connected by a tricritical point. This study on the one hand demonstrates that the intelligent matter with a nonlinear adaptive interaction can exhibit qualitatively different phase behaviors from conventional matter, and on the other hand shows that, during voting, even unbiased feedback may possibly induce spontaneous symmetry breaking, leading to a biased outcome where one side of the vote becomes favored.
Statistical Mechanics (cond-mat.stat-mech), Soft Condensed Matter (cond-mat.soft)
19 pages, 5 Figures
Machine Learning Band Gap Predictions: Linking Quasiparticle Self-Consistent GW and LDA-Derived Partial Density of States
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-28 20:00 EDT
Shota Tankano, Takao Kotani, Masao Obata, Kazunori Sato, Harutaka Saito, Tatsuki Oda
Accurately calculating band gaps for given crystal structures is highly desirable. However, conventional first-principles calculations based on density functional theory (DFT) within the local density approximation (LDA) fail to predict band gaps accurately. To address this issue, the quasi-particle self-consistent GW (QSGW) method is often employed as it is one of the most reliable theoretical approaches for predicting band gaps. Despite its accuracy, QSGW requires significant computational resources. To overcome this limitation, we propose combining QSGW with machine learning. In this study, we applied QSGW to 1,516 materials from the Materials Project [this https URL] and used machine learning to predict QSGW band gaps as a function of the partial density of states (PDOS) in LDA. Our results demonstrate that the proposed model significantly outperforms linear regression approaches with linearly-independent descriptor generation [this https URL]. This model is a prototype for predicting material properties based on PDOS.
Materials Science (cond-mat.mtrl-sci)
Stabilization of the collinear plateau phase by thermal fluctuations in the disordered triangular lattice antiferromagnet Rb${(1-x)}$K${x}$Fe(MoO$_4$)$_2$
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-07-28 20:00 EDT
V.N. Glazkov, I.A. Krastilevskiy
The triangular lattice antiferromagnet RbFe(MoO$ _4$ )$ 2$ orders antiferromagnetically in a planar 120$ ^\circ$ -structure below $ T\textrm{N}\approx 4$ K. A striking feature of RbFe(MoO$ _4$ )$ 2$ magnetic phase diagram is the presence of collinear ``1/3-plateau’’ magnetic phase, which is stabilized by thermal and quantum fluctuations at magnetization $ M\approx \frac{1}{3} M\textrm{sat}$ . Static disorder caused by impurities is predicted to act against the effect of fluctuations and to suppress collinear plateau phase (Maryasin and Zhitomirsky, PRL 111, 247201 (2013)). Balance between dynamic'' thermal and quantum fluctuations and static’’ impurity-induced disorder is temperature-sensitive, which allows thermal fluctuations to take over the effect of static disorder and leads to the revival of the fluctuation-stabilized ``1/3-plateau’’ phase on heating. Here we present experimental results directly confirming this prediction and demonstrating re-establishment of the plateau-like phase in the diluted Rb$ _{(1-x)}$ K$ _{x}$ Fe(MoO$ _4$ )$ _2$ sample at moderate dilution level $ x=15$ % on heating as the effect of thermal fluctuations increases.
Strongly Correlated Electrons (cond-mat.str-el)
10 pages, 8 figures
Incommensurate magnetic order arising from frustrated interchain interactions in the spin-1/2 chain compound AgCuVO$_4$
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-07-28 20:00 EDT
A. Hromov, A. Zorko, M. Gomilšek, I. Puente Orench, L. Keller, T. Shiroka, A. Prokofiev, M. Pregelj
Quantum spin chains with competing interactions offer a platform where low dimensionality and frustration–both acting to suppress magnetic order–intersect. We studied magnetic ordering in the spin-1/2 chain compound AgCuVO$ 4$ using muon spin spectroscopy and neutron diffraction. Long-range magnetic order emerges at $ T_N = 2.0(1)$ K, which is $ \sim$ 1/200 of the dominant intrachain coupling $ J$ and $ \sim$ 1/15 of the interchain interactions. The collinear incommensurate amplitude-modulated magnetic structure features a reduced ordered moment of 0.13(2) $ \mu\mathrm{B}$ , confined to the $ ab$ plane and modulated along the $ c$ axis–perpendicular to the spin chains–indicating frustrated interchain couplings. The low $ T_N$ , small moment, and incommensurate order highlight strong frustration, positioning AgCuVO$ _4$ as a model system for exploring frustration in quantum spin chains.
Strongly Correlated Electrons (cond-mat.str-el)
6 pages, 4 figures
Micromechanics of compressive and tensile forces in partially-bonded granular materials
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-07-28 20:00 EDT
Abrar Naseer, Karen E. Daniels, Tejas G. Murthy
In granular media, the presence of even small amounts of interparticle cohesion manifests as an increase in the bulk strength and stiffness, effects that are typically associated with an increase in the average number of constraints per particle. By performing an ensemble of isotropic compression experiments, all starting from the same initial particle configuration but with varying fraction of bonded particles, we use photoelastic force measurements to identify the causes of this phenomenon at the particle-scale and meso-scale. As a function of the percentage of bonded particles, we measure a small decrease in the critical packing fraction at which jamming occurs. Above jamming, the local pressure increases predominantly for the bonded particles, measured relative to the unbonded case, through approximately equal contributions of both tensile and compressive forces. Histograms of the magnitude of the interparticle forces become broader for systems with more bonded particles. We measure both pressure and coordination number as a function of distance from a bonded dimer, both of which are locally enhanced for nearest neighbors, indicating that dimers appear to act as areas of concentrated force and connectivity that improve rigidity.
Soft Condensed Matter (cond-mat.soft)
6 pages, 4 figures, 4 pages supplementary material, 4 figures
Dirac points annihilation and its obstruction characterized by Euler number and quaternionic charges in kagome lattice
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-07-28 20:00 EDT
M. Finck, D. Solnyshkov, J. Dubois, G. Malpuech
We investigate the topological phenomenon of Dirac point annihilation and its obstruction in three-band, real symmetric Hamiltonians with time-reversal symmetry, and their relation to the Euler number, a well-known topological invariant. For this purpose, we study the example of the kagome lattice using a simple tight-binding model. By tuning the parameters of the lattice continuously, we illustrate situations where two Dirac points are able to annihilate, and others, where this annihilation is topologically obstructed. For a system with no gaps between the three bands, like in the kagome lattice, the Euler number of two bands is ill-defined on the whole Brillouin zone, which requires the introduction of the so-called ``patch” Euler number on a subregion without additional degeneracies coming from the third band. A non-zero patch Euler number means that the annihilation of the Dirac points is impossible. We also illustrate another point of view, using homotopy theory, associating the Dirac points with quaternionic charges. We prove that the non-abelian braiding of the Dirac points in k-space conjugates their quaternionic charge and explains the possible obstruction to the annihilation of Dirac points. Finally, we show that the proposed deformation of the kagome lattice can be achieved in realistic photonic systems.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Mathematical Physics (math-ph)
Shape-dependent direction reversal in anisotropic catalytic microswimmers
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-07-28 20:00 EDT
Solenn Riedel, Mengshi Wei, Daniela J. Kraft
The propulsion direction of active particles is a key feature in self-propelled systems and depends on the propulsion mechanism and environmental conditions. Here, using 3D micro-printed catalytically active particles, we experimentally show that the propulsion direction can change with increasing fuel concentration when the active particle possesses an anisotropic shape. We find that discs, tori, and bent rods reverse their direction of motion with increasing hydrogen peroxide concentration–moving with their inert side forward at low concentrations and with their catalytic side forward at high concentrations. In contrast, spheres and straight rods do not exhibit this reversal. We observe that direction reversal is independent of the base material composition of the swimmer and its size, and only occurs for anisotropic particles where, due to their elongated shape, the location of the solute concentration maximum is unstable and can be shifted by substrate-induced confinements. Our measurements suggest that in addition a change in the platinum-catalyzed reaction of hydrogen peroxide occurs, to which particles with elongated shapes that induce sufficient confinement are more sensitive.
Soft Condensed Matter (cond-mat.soft), Materials Science (cond-mat.mtrl-sci), Chemical Physics (physics.chem-ph)
Eliminating leading and subleading corrections to scaling in the three-dimensional XY universality class
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-07-28 20:00 EDT
We study the $ (q+1)$ -state clock model on the simple cubic lattice by using Monte Carlo simulations. In addition to the nearest neighbor coupling we consider a next-to-next-to-nearest neighbor coupling. For a certain range of the parameters, the phase transition of the model shares the XY universality class. Leading corrections to scaling are studied by using finite size scaling of dimensionless quantities, such as the Binder cumulant $ U_4$ . The spatial unisotropy, which causes subleading corrections, is studied by computing the exponential correlation length $ \xi_{exp}$ in the high temperature phase for different directions. In the case of the $ q$ -state clock model it turns out that by tuning the ratio of the two coupling constants, we can eliminate either leading or subleading corrections to scaling. These points on the critical line are close to each other. Hence in the improved model, where leading corrections to scaling vanish, also subleading corrections are small. By using a finite size scaling analysis of our high statistics data we obtain $ \eta=0.03816(2)$ and $ y_t =1/\nu=1.48872(5)$ as estimates of the critical exponents.
Statistical Mechanics (cond-mat.stat-mech), High Energy Physics - Lattice (hep-lat)
42 pages, 9 figures
Controlling Topological Defects in Polar Fluids via Reinforcement Learning
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-07-28 20:00 EDT
Abhinav Singh, Petros Koumoutsakos
Topological defects in active polar fluids exhibit complex dynamics driven by internally generated stresses, reflecting the deep interplay between topology, flow, and non-equilibrium hydrodynamics. Feedback control offers a powerful means to guide such systems, enabling transitions between dynamic states. We investigated closed-loop steering of integer-charged defects in a confined active fluid by modulating the spatial profile of activity. Using a continuum hydrodynamic model, we show that localized control of active stress induces flow fields that can reposition and direct defects along prescribed trajectories by exploiting non-linear couplings in the system. A reinforcement learning framework is used to discover effective control strategies that produce robust defect transport across both trained and novel trajectories. The results highlight how AI agents can learn the underlying dynamics and spatially structure activity to manipulate topological excitations, offering insights into the controllability of active matter and the design of adaptive, self-organized materials.
Soft Condensed Matter (cond-mat.soft), Artificial Intelligence (cs.AI), Machine Learning (cs.LG)
Fermi liquid and isotropic superconductivity of Hund scenario for bilayer nickelates
New Submission | Superconductivity (cond-mat.supr-con) | 2025-07-28 20:00 EDT
Recent experiments on bulk and thin film bilayer nickelate high-$ T_c$ superconductors urge for clarification of their pairing mechanism. Debates exist on whether the hybridization or the Hund’s coupling between the nickel $ d_{x^2-y^2}$ and $ d_{z^2}$ orbitals plays a primary role in driving the superconductivity. Here, we study the Hund scenario and make comparisons with the hybridization scenario using the same dynamic Schwinger boson approach. Our calculations reveal several key features of the Hund-driven superconductivity, including an isotropic $ s$ -wave gap, a lower maximum $ T_c$ , and Fermi liquid normal states, that differ from the hybridization-driven mechanism. We attribute these differences to their distinct low-energy dynamics. Comparison with recent experiments suggests that the Hund scenario alone is not enough to explain the bilayer nickelate superconductivity in both bulk and thin films.
Superconductivity (cond-mat.supr-con)
Stability and Symmetry-Assured Crystal Structure Generation for Inverse Design of Photocatalysts in Water Splitting
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-28 20:00 EDT
Zhilong Song, Chongyi Ling, Qiang Li, Qionghua Zhou, Jinlan Wang
Generative models are revolutionizing materials discovery by enabling inverse design-direct generation of structures from desired properties. However, existing approaches often struggle to ensure inherent stability and symmetry while precisely generating structures with target compositions, space groups, and lattices without fine-tuning. Here, we present SSAGEN (Stability and Symmetry-Assured GENerative framework), which overcomes these limitations by decoupling structure generation into two distinct stages: crystal information (lattice, composition, and space group) generation and coordinate optimization. SSAGEN first generates diverse yet physically plausible crystal information, then derives stable and metastable atomic positions through universal machine learning potentials, combined global and local optimization with symmetry and Wyckoff position constraints, and dynamically refined search spaces. Compared to prior generative models such as CDVAE, SSAGEN improves the thermodynamic and kinetic stability of generated structures by 148% and 180%, respectively, while inherently satisfying target compositions, space groups, and lattices. Applied to photocatalytic water splitting (PWS), SSAGEN generates 200,000 structures-81.2% novel-with 3,318 meeting all stability and band gap criteria. Density functional theory (DFT) validation confirms 95.6% structures satisfy PWS requirements, with 24 optimal candidates identified through comprehensive screening based on electronic structure, thermodynamic, kinetic, and aqueous stability criteria. SSAGEN not only precisely generates materials with desired crystal information but also ensures inherent stability and symmetry, establishing a new paradigm for targeted inverse design of functional materials.
Materials Science (cond-mat.mtrl-sci)
Human-AI Synergy in Adaptive Active Learning for Continuous Lithium Carbonate Crystallization Optimization
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-28 20:00 EDT
Shayan S. Mousavi Masouleh, Corey A. Sanz, Ryan P. Jansonius, Cara Cronin, Jason E. Hein, Jason Hattrick-Simpers
As demand for high-purity lithium surges with the growth of the electric vehicle (EV) industry, cost-effective extraction from lower-grade North American sources like the Smackover Formation is critical. These resources, unlike high-purity South American brines, require innovative purification techniques to be economically viable. Continuous crystallization is a promising method for producing battery-grade lithium carbonate, but its optimization is challenged by a complex parameter space and limited data. This study introduces a Human-in-the-Loop (HITL) assisted active learning framework to optimize the continuous crystallization of lithium carbonate. By integrating human expertise with data-driven insights, our approach accelerates the optimization of lithium extraction from challenging sources. Our results demonstrate the framework’s ability to rapidly adapt to new data, significantly improving the process’s tolerance to critical impurities like magnesium from the industry standard of a few hundred ppm to as high as 6000 ppm. This breakthrough makes the exploitation of low-grade, impurity-rich lithium resources feasible, potentially reducing the need for extensive pre-refinement processes. By leveraging artificial intelligence, we have refined operational parameters and demonstrated that lower-grade materials can be used without sacrificing product quality. This advancement is a significant step towards economically harnessing North America’s vast lithium reserves, such as those in the Smackover Formation, and enhancing the sustainability of the global lithium supply chain.
Materials Science (cond-mat.mtrl-sci), Other Condensed Matter (cond-mat.other), Human-Computer Interaction (cs.HC), Machine Learning (cs.LG), Data Analysis, Statistics and Probability (physics.data-an)
Quantum Droplets of Light in Semiconductor Microcavities
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-07-28 20:00 EDT
Matteo Caldara, Olivier Bleu, Francesca Maria Marchetti, Jesper Levinsen, Meera M. Parish
Quantum droplets are dilute self-bound configurations of bosons that result from the balance between a mean-field attraction and a repulsion induced by quantum fluctuations. Such droplets have been successfully realized in cold atomic gases and represent a signature of their quantum nature. Here, we predict the existence of a similar droplet phase in a solid-state system, involving polaritons formed from the strong coupling between excitons (bound electron-hole pairs) and photons in a semiconductor microcavity. We consider a spin mixture of exciton-polaritons near a biexciton Feshbach resonance, which allows one to tune the interspecies interactions to be attractive and comparable in magnitude to the intraspecies repulsion. We find that self-bound quantum droplets are achievable for realistic parameters in atomically thin semiconductors, and that they can be detected via their excitation spectrum and spatial profile. This exotic phase could potentially lead to polariton condensation at lower thresholds and it opens an alternative avenue to achieve the long-sought quantum polaritonic regime.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Quantum Gases (cond-mat.quant-gas)
8+14 pages | 3+4 figures | Comments are welcome!
Atomically clean free-standing two-dimensional materials through heating in ultra-high vacuum
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-28 20:00 EDT
Philipp Irschik, David Lamprecht, Shrirang Chokappa, Clemens Mangler, Carsten Speckmann, Thuy An Bui, Manuel Längle, Lado Filipovic, Jani Kotakoski
Surface contamination not only influences but in some cases even dominates the measured properties of two-dimensional materials. Although different cleaning methods are often used for contamination removal, commonly used spectroscopic cleanliness assessment methods can leave the level of achieved cleanliness ambiguous. Despite two decades of research on 2D materials, the true cleanliness of the used samples is often left open to interpretation. In this work, free-standing monolayer graphene and hexagonal boron nitride are annealed at different temperatures in a custom-built ultra-high vacuum heating chamber, connected to a scanning transmission electron microscope via a vacuum transfer line, enabling atomically resolved cleanliness characterization as a function of annealing temperature, while eliminating the introduction of airborne contamination during sample transport. While annealing at 200 °C already reduces contamination significantly, it is not until 400 °C or higher, where over 90% of the free-standing monolayer areas are atomically clean. At this point, further contamination removal is mainly limited by defects in the material and metal contamination introduced during the sample transfer or growth. The achieved large, atomically clean areas can then be used for further nanoscale engineering steps or device processing, facilitating interaction with the material rather than contamination.
Materials Science (cond-mat.mtrl-sci)
51 pages, 4 figures in main text and 21 figures in supplement
Time-energy tradeoff in stochastic resetting using optimal control
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-07-28 20:00 EDT
Rémi Goerlich, Kristian Stølevik Olsen, Hartmut Löwen, Yael Roichman
Stochastic resetting is a driving mechanism that is known to minimize the first passage time to reach a target, at the cost of energy expenditure. The choice of the physical implementation of each resetting event determines the tradeoff between the acceleration of the search process and its energetic cost. Here, we present an optimal transport protocol that balances the duration and the energetic cost of each resetting event. This protocol drives a harmonically trapped Brownian particle between two equilibrium states within a finite time and with minimal energetic cost. An explicit comparison with other types of finite-time protocols further shows its specific thermodynamic properties. Its cost is both a lower bound on the cost of unoptimized shortcut protocols and an upper bound on the cost of optimal protocols which do not ensure final equilibrium. When applying the optimal transport protocol to implement stochastic resetting, a single lower time-energy bound is reached: this protocol allows to reach the best tradeoff between energetic cost and search time.
Statistical Mechanics (cond-mat.stat-mech), Soft Condensed Matter (cond-mat.soft)
Measurement and Qualitative Explanation of Decay Lengths of Attractive and Repulsive Forces between Natural and Artificial Atoms
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-07-28 20:00 EDT
Marco Weiss, Fabian Stilp, Max Reinhart, Franz J. Giessibl
Artificial atoms, such as quantum corrals, offer an excellent platform to study fundamental interactions between localized quantum states and nanoscale probes. We performed atomic force microscopy measurements inside square quantum corrals on Cu(111) using CO- and metal-terminated tips. Using chemically unreactive CO-terminated tips repulsive Pauli forces can be probed, while metallic tips are attracted to the localized quantum states due to chemical bonding. We found distinct exponential decay constants of 46 pm for the repulsive and 66 pm for the attractive forces. Attractive and repulsive interactions between two natural atoms show significantly shorter decay lengths. While natural atoms feature states with a broad range of decay lengths, including very short ones from deeply bound states, quantum corrals are lacking such deeply bound and highly localized states, resulting in longer decay lengths. These results offer a new route to understand and design atomic-scale interactions in low-dimensional quantum structures and devices.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
The gauge theory dual of the bilayer XY model with second order Josephson coupling
New Submission | Superconductivity (cond-mat.supr-con) | 2025-07-28 20:00 EDT
We formulate a duality transformation for a bilayer XY model where the layers are coupled by second order Josephson effect, which favors inter-layer phase difference of either $ 0$ or $ \pi$ . The model may represent a bilayer superconductor or a spin-1 ferromagnetic Bose gas in the easy-plane limit. The second order Josephson term is mapped to a U(1) gauge field, known to be trivially confining in two dimensions, and we argue that a Coulomb-gas analysis is not applicable to the dual theory. Instead, we appeal to the vast knowledge of gauge theory and infer that the only phase transition out of low-temperature ordered phase is an Ising transition driven by condensation of $ \mathbb{Z}_2$ domain wall loops. The domain wall loops can be seen as a surviving vestige of single-layer vortex-anti-vortex pair, heavily deformed by the second order Josephson coupling. A theoretical or computational method that concentrates on point defects would most likely miss out on these excitations and reach erroneous results. Our dual theory offers a clear, intuitive picture of how the second order Josephson coupling induces confinement of vortices and drastically changes the physics.
Superconductivity (cond-mat.supr-con)
From weakly interacting spinons to tightly bound triplons in the frustrated quantum spin-Peierls chain
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-07-28 20:00 EDT
Pyeongjae Park, Bo Xiao, Karolina Górnicka, Andrew F. May, Jiaqiang Yan, Ryoichi Kajimoto, Mitsutaka Nakamura, Matthew B. Stone, Gábor B. Halász, Andrew D. Christianson
Fractionalized quasiparticles and their confinement into emergent bound states lie at the heart of modern quantum magnetism. While the evolution into magnonic bound states has been well characterized, experimental insight into the analogous transition to triplons remains limited. Here, using high-resolution neutron spectroscopy and state-of-the-art spin dynamics simulations, we uncover the transformation from weakly interacting spinons to tightly bound triplons in the spin-Peierls compound CuGeO3. Quantitative comparisons between the measured spectra and tensor network simulations reveal substantial next-nearest-neighbor frustration and weak external dimerization, placing the system deep within the spontaneously dimerized regime and near the exactly solvable Majumdar-Ghosh point. We further show an energy- and temperature-dependent evolution between two contrasting quasiparticle regimes: deconfined spinons with markedly suppressed interactions by frustration, and coherent triplonic bound states with no observable spinon degrees of freedom. Remarkably, triplon character persists into the two-particle regime, forming a structured two-triplon continuum with a spectral feature associated with a van Hove singularity at its lower boundary. These findings challenge the conventional view that robust triplons require strong external dimerization and demonstrate how the interplay between frustration and dimerization can reshape fractionalization and confinement.
Strongly Correlated Electrons (cond-mat.str-el), Materials Science (cond-mat.mtrl-sci)
13 pages, 4 figures
Solute Segregation Activates Unconventional Grain Boundary Disconnections
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-28 20:00 EDT
Disconnections, now recognized as key mediators of grain boundary (GB) kinetics in polycrystals, have traditionally been associated with thermal or mechanical activation. Here, using atomistic simulations across multiple binary alloys (Al-Ni, Al-Fe, etc.), we reveal a distinct disconnection formation mechanism solely activated by interstitial solute segregation. This process exhibits a zero-nucleation energy barrier, contrasting sharply with conventional disconnection nucleation. We identify two segregation-induced disconnection types: (i) annihilable disconnections that promote GB migration and annihilate with continued segregation, and (ii) permanent disconnections with stable dipoles that resist shear, inducing GB amorphization and sliding rather than conventional shear-coupled motion. The permanent disconnections generate localized stress fields that further drive solute accumulation and, at higher concentrations, facilitate precipitation. These disconnections, unprecedented in pure systems, follow unique nucleation pathways as confirmed by dichromatic pattern analysis and persist across diverse crystal structures. This work establishes solute segregation as a route for barrier-free disconnection formation, fundamentally altering our understanding of GB kinetics in alloys.
Materials Science (cond-mat.mtrl-sci)
maintext: 13 pages, 4 figures; supplemental: 12 pages, 9 figures
Equivariant machine learning of Electric Field Gradients – Predicting the quadrupolar coupling constant in the MAPbI$_3$ phase transition
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-28 20:00 EDT
Bernhard Schmiedmayer, J.W. Wolffs (Jop), Gilles A. de Wijs, Arno P.M. Kentgens, Jonathan Lahnsteiner, Georg Kresse
We present a strategy combining machine learning and first-principles calculations to achieve highly accurate nuclear quadrupolar coupling constant predictions. Our approach employs two distinct machine-learning frameworks: a machine-learned force field to generate molecular dynamics trajectories and a second model for electric field gradients that preserves rotational and translational symmetries. By incorporating thermostat-driven molecular dynamics sampling, we enable the prediction of quadrupolar coupling constants in highly disordered materials at finite temperatures. We validate our method by predicting the tetragonal-to-cubic phase transition temperature of the organic-inorganic halide perovskite MAPbI$ _3$ , obtaining results that closely match experimental data.
Materials Science (cond-mat.mtrl-sci)
11 pages, 7 figures
Gradient-based grand canonical optimization enabled by graph neural networks with fractional atomic existence
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-28 20:00 EDT
Mads-Peter Verner Christiansen, Bjørk Hammer
Machine learning interatomic potentials have become an indispensable tool for materials science, enabling the study of larger systems and longer timescales. State-of-the-art models are generally graph neural networks that employ message passing to iteratively update atomic embeddings that are ultimately used for predicting properties. In this work we extend the message passing formalism with the inclusion of a continuous variable that accounts for fractional atomic existence. This allows us to calculate the gradient of the Gibbs free energy with respect to both the Cartesian coordinates of atoms and their existence. Using this we propose a gradient-based grand canonical optimization method and document its capabilities for a Cu(110) surface oxide.
Materials Science (cond-mat.mtrl-sci), Machine Learning (cs.LG)
Interplay of non-Hermitian skin effect and electronic correlations in the non-Hermitian Hubbard model via Real-space dynamical mean field theory
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-07-28 20:00 EDT
Chakradhar Rangi, Juana Moreno, Ka-Ming Tam
Non-Hermitian quantum systems, characterized by their ability to model open systems with gain and loss, have unveiled striking phenomena such as the non-Hermitian skin effect (NHSE), where eigenstates localize at boundaries under open boundary conditions. While extensively studied in non-interacting systems, the interplay between NHSE and strong electron correlations remains largely unexplored. Here, we investigate the non-Hermitian Hubbard model with asymmetric hopping, employing real-space dynamical mean-field theory (R-DMFT), a novel extension to such non-Hermitian correlated models-to capture both local correlations and spatial inhomogeneities. By analyzing the end-to-end Green’s function as probes of directional amplification, we demonstrate that strong correlations can suppress the skin effect, leading to a crossover from boundary-dominated to correlation-driven dynamics. Our systematic study reveals that correlations dominate at small to intermediate strength of asymmetric hopping, inducing exponential decay in the end-to-end Green’s function, but higher strength of asymmetric hopping can restore amplification even at strong interaction. These results illuminate the tunable interplay between correlations and non-Hermitian physics, suggesting avenues for engineering non-reciprocal transport in correlated open quantum systems.
Strongly Correlated Electrons (cond-mat.str-el), Other Condensed Matter (cond-mat.other)
8 pages, 4 figures