CMP Journal 2025-10-27
Statistics
Nature: 3
Nature Nanotechnology: 1
Nature Reviews Materials: 1
Physical Review Letters: 3
arXiv: 53
Nature
Direct deaminative functionalization with N-nitroamines
Original Paper | Synthetic chemistry methodology | 2025-10-26 20:00 EDT
Guangliang Tu, Ke Xiao, Xiaoping Chen, Haoran Xu, Haifeng Zeng, Fangjiang Zhang, Xiaosong Xue, Xiaheng Zhang
Amines are among the most common functional groups in bioactive molecules1. Despite this prevalence, conventional means of converting aromatic amines rely heavily on diazonium intermediates2, which pose significant safety risks due to the explosive nature of these salts3,4. Here, we report a direct deaminative strategy through the formation of N-nitroamines, allowing the direct conversion of inert aromatic C-N bonds into an array of other functional groups, C-X (C-Br, C-Cl, C-I, C-F, C-N, C-S, C-Se, C-O) and C-C bonds. This operationally simple, general protocol establishes a unified strategy for one-pot deaminative cross-couplings by integrating deaminative functionalization with transition-metal-catalyzed arylation, thereby streamlining synthesis and late-stage functionalization. The key advantages of this transformation over other deaminative functionalization methods lies in its versatility across nearly all classes of medicinally relevant heteroaromatic amines, as well as electronically and structurally diverse aniline derivatives, regardless of the position of the amino group. Mechanistic studies, supported by both experimental observations and theoretical analysis, suggest that the aryl cation equivalent reactivity of N-nitroamines is generally favoured in this deaminative process. This study highlights the significant potential of the direct deamination approach in synthetic chemistry, offering a safer alternative to the traditionally explosive and hazardous aryldiazonium chemistry.
Synthetic chemistry methodology
A matrix-confined molecular layer for perovskite photovoltaic modules
Original Paper | Solar cells | 2025-10-26 20:00 EDT
Yugang Liang, Guodong Chen, Yao Wang, Yu Zou, Menglei Feng, Yanming Wang, Bowei Li, Yuljae Cho, Yide Chang, Tianle Liu, Taiyang Zhang, Yongbing Lou, Ranran Xu, Lei Lu, Ni Zhang, Ke Meng, Chen Zhu, Chuying Ouyang, Yanfeng Miao, Yongsheng Guo, Yuetian Chen, Yixin Zhao
Metal halide perovskites with remarkable optoelectronic properties have become a competitive candidate for supporting the efficiency progression of photovoltaics. As the latest record on power conversion efficiency (PCE) of research-cells being comparable to the commercialized silicon cells1-3, the industrialization of perovskite solar cells (PSCs) is on the horizon4,5. Most high-efficiency inverted perovskite solar cells using self-assembled molecules (SAMs) face the challenges due to their aggregation and hydrophobicity. Here we report a “SAM-in-matrix” strategy to distribute partial SAMs into a stable matrix of tris(pentafluorophenyl)borane, which could break the original molecular stacking-induced aggregation. 2D lattice Monte Carlo simulation and experimental results reveal that such strategy can form efficient charge transport channels. This SAM-in-matrix hole transport layer (HTL)-based devices demonstrate universally higher efficiencies for various SAMs with compact surface coverage, decent conductivity, and greatly reduced buried nanovoids. Moreover, this strategy shows prominent applicational potential for scalable production. The SAM-in-matrix HTL on FTO/NiOx substrate facilitates the formation of large-area perovskite films with good crystalline quality and enhanced conductivity of NiOx. 1 m × 2 m large-area perovskite solar module is thus achieved with a certified record efficiency of 20.05%.
Solar cells
All-perovskite tandem solar cells with dipolar passivation
Original Paper | Solar cells | 2025-10-26 20:00 EDT
Renxing Lin, Han Gao, Jing Lou, Jian Xu, Mengran Yin, Pu Wu, Chenshuaiyu Liu, Yijia Guo, Enzuo Wang, Shuncheng Yang, Runnan Liu, Dong Zhou, Changzeng Ding, Anh Bui, Ni Yin, Daniel H. Macdonald, Changqi Ma, Qi Chen, Ke Xiao, Xin Luo, Ye Liu, Ludong Li, Yongxi Li, Chao Chang, Hairen Tan
Non-radiative recombination loss at the hole transport layer (HTL)/perovskite interface in the narrow-bandgap (NBG) subcell constrains the power-conversion efficiency (PCE) of all-perovskite tandem solar cells 1,2. Minimizing charge recombination at the buried interface of lead-tin (Pb-Sn) based NBG perovskite solar cells have proven particularly challenging, as conventional long-chain amine-based passivation strategies often induce carrier transport losses, thereby limiting both the fill factors (FF) and short-circuit current density (Jsc) 3-5. Here, we developed a dipolar passivation strategy that reduces the trap density at the buried interface of mixed Pb-Sn perovskite while simultaneously enabling precise energy level alignment at the HTL/perovskite interface. This dipolar-induced passivation enhances ohmic contact, facilitating efficient hole injection into the HTL and repelling electrons from the HTL/Pb-Sn perovskite interface. This approach extends the carrier diffusion length to 6.2 μm and enables a substantial enhancement in the PCE of Pb-Sn perovskite solar cells, achieving 24.9% along with an open-circuit voltage (Voc) of 0.911 V, a Jsc of 33.1 mA cm-2 and a high FF of 82.6%. Furthermore, the dipolar passivation effectively mitigates contact losses in the NBG subcell induced by the interconnecting layer of tandem devices, contributing to an outstanding PCE of 30.6% (certified stabilized 30.1%) in all-perovskite tandem solar cells.
Solar cells
Nature Nanotechnology
A quantum resistance memristor for an intrinsically traceable International System of Units standard
Original Paper | Electronic and spintronic devices | 2025-10-26 20:00 EDT
Gianluca Milano, Xin Zheng, Fabio Michieletti, Giuseppe Leonetti, Gabriel Caballero, Ilker Oztoprak, Luca Boarino, Özgür Bozat, Luca Callegaro, Natascia De Leo, Isabel Godinho, Daniel Granados, Itir Koymen, Mariela Menghini, Enrique Miranda, Luís Ribeiro, Carlo Ricciardi, Jordi Suñe, Vitor Cabral, Ilia Valov
The recent revision of the International System of Units (SI)–which fixed the numerical values of nature’s fundamental constants–has opened new perspectives for practical realizations of SI units. Here we demonstrate an intrinsic resistance standard based on memristive nanoionic cells that operate in air at room temperature and are directly accessible to end users. By driving these devices into the quantum conductance regime and using an electrochemical-polishing-based programming strategy, we achieved quantum conductance levels that can be exploited as intrinsic standard values. An interlaboratory comparison confirmed metrological consistency, with deviations of -3.8% and 0.6% from the agreed SI values for the fundamental quantum of conductance, G0, and 2G0, respectively. These results lay the groundwork for the implementation of national metrology institute services on chip and for the development of self-calibrating measurement systems with zero-chain traceability.
Electronic and spintronic devices, Electronic devices
Nature Reviews Materials
Dimensionality engineering of perovskites for stable heterojunction-based photovoltaics
Review Paper | Solar cells | 2025-10-26 20:00 EDT
Randi Azmi, Drajad Satrio Utomo, Yanping Liu, Shynggys Zhumagali, Stefaan De Wolf
Commercial solar cells require long-term operational stability. Despite their high performance, perovskite solar cells degrade owing to defects, impurities and mobile ions in the bulk and at the surface of their photo-absorbing 3D metal-halide perovskite films. Compared with 3D perovskites, low-dimensional (LD) perovskites exhibit greater phase stability and superior ambient, light and thermal stability. Notably, by forming 3D/LD heterostructures, these LD layers can also passivate defective 3D perovskite surfaces through surface reconstruction. However, this approach can increase energy mismatch and structural disorder at the contact interfaces owing to excess unbonded ligands. The LD perovskite capping layers can also feature mixed phases, random orientations and other inhomogeneities, which can create charge recombination channels, jeopardize charge transport and undermine long-term stability. Moreover, the monovalent ammonium-based ligands (phenethylammonium and butylammonium) commonly used to create 3D/LD heterojunctions are relatively unstable owing to weak van der Waals interactions btween the organic sheets and the inorganic framework, as well as their relatively low acid dissociation constant (pKa), which make them prone to deprotonation. To improve stability, it is thus imperative to use suitable organic ligands that form strong coordination bonds with the inorganic framework – ideally multivalent amines with high pKa values. Here, we review instability mechanisms at 3D/LD interfaces and discuss mitigation strategies, focusing on ligand chemistry and the fabrication of phase-pure, homogeneous LD capping layers to improve 3D/LD perovskite heterostructure stability.
Solar cells
Physical Review Letters
Apparent $w<-1$ and a Lower ${S}_{8}$ from Dark Axion and Dark Baryons Interactions
Article | Cosmology, Astrophysics, and Gravitation | 2025-10-27 06:00 EDT
Justin Khoury, Meng-Xiang Lin, and Mark Trodden
We show that a simple coupling between dark energy and dark matter can simultaneously address two distinct hints at new physics coming from cosmological observations. The first is the recent evidence from the DESI project and supernovae observations that the dark energy equation of state is evolvi…
Phys. Rev. Lett. 135, 181001 (2025)
Cosmology, Astrophysics, and Gravitation
Free Energy Source of the Mirror Instability: Nonresonant Particles
Article | Plasma and Solar Physics, Accelerators and Beams | 2025-10-27 06:00 EDT
Xudong Guo, Jinsong Zhao, Kristopher G. Klein, and Huasheng Xie
The mirror instability is a fundamental phenomenon in plasma physics. Given the historical discussion regarding the role of resonant particles in driving this instability--which is at odds with its presence in magnetohydrodynamic (MHD) models that only describe fluid plasma behavior--we seek to clarif…
Phys. Rev. Lett. 135, 185201 (2025)
Plasma and Solar Physics, Accelerators and Beams
Body-Centered-Cubic Phase Transformation in Gold at TPa Pressures
Article | Condensed Matter and Materials | 2025-10-27 06:00 EDT
Amy L. Coleman, Saransh Singh, Tom E. Lockard, Ian K. Ocampo, Amy E. Lazicki, Martin G. Gorman, Stefano Racioppi, Andrew G. Krygier, Christopher E. Wehrenberg, Rasool Ahmad, Marius Millot, Sebastien Hamel, Sirus Han, Mary Kate Ginnane, Damian C. Swift, Stanimir A. Bonev, Eva Zurek, Thomas S. Duffy, Jon H. Eggert, James McNaney, and Raymond F. Smith
In situ x-ray diffraction at both the National Ignition Facility and Omega-EP Laser Facility has been utilized to determine the crystallographic state of ramp and shock-ramp compressed gold up to 1.2 TPa ( atmospheres). In this Letter, we describe a series of experiments that e…
Phys. Rev. Lett. 135, 186101 (2025)
Condensed Matter and Materials
arXiv
A Universal Chern Model on Arbitrary Triangulations
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-10-27 20:00 EDT
Given a triangulation of a closed orientable surface, we consider the lattice with sites at the vertices, edges and facets of the triangulation. Borrowing from mathematics literature, we introduce on this lattice a pair of tight-binding Hamiltonians derived from the boundary and Poincaré duality maps of finite simplicial manifolds. These Hamiltonians have been proved to have clean topological spectral gaps carrying non-trivial Chern numbers in the limit of infinite refinement of the triangulation. We confirm this via numerical simulations, and demonstrate how these models enable topological edge modes at the surfaces of real-world objects. Furthermore, we describe a metamaterial whose dynamics reproduces that of the proposed model, thus bringing the topological metamaterials closer to real-world applications.
Strongly Correlated Electrons (cond-mat.str-el), Materials Science (cond-mat.mtrl-sci), Mathematical Physics (math-ph), Operator Algebras (math.OA)
Fluxoid solitons in superconducting tapered tubes and bottlenecks
New Submission | Superconductivity (cond-mat.supr-con) | 2025-10-27 20:00 EDT
Tim Kokkeler, Mateo Uldemolins, Francisco Lobo, F. Sebastian Bergeret, Elsa Prada, Pablo San-Jose
A thin-walled tubular superconductor develops a quantized fluxoid in the presence of an axial magnetic field. The fluxoid corresponds to the number of phase windings of the superconducting order parameter and is topological in nature. When the tube has a radius variation along the axial direction, forming a bottleneck structure between sections with different radius, a fluxoid mismatch can appear depending on the applied magnetic field. The bottleneck then becomes a topological boundary and is host to topologically protected solutions for the order parameter, dubbed fluxoid solitons, that are free to move around bottlenecks with cylindrical symmetry. Fluxoid solitons are a new type of vortex with non-quantized flux, loosely related to Pearl vortices in thin superconducting films and fluxons in Corbino Josephson junctions. We characterize their properties as a function of system parameters using the self-consistent quasiclassical theory of diffusive superconductors. We consider both short bottleneck structures and long tapered tubes, where multiple trapped fluxoid solitons adopt elaborate arrangements dictated by their mutual repulsion.
Superconductivity (cond-mat.supr-con)
15 pages (2 appendices and 7 figures)
$\mathbb{Z}_2$ lattice gauge theories: fermionic gauging, transmutation, and Kramers-Wannier dualities
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-10-27 20:00 EDT
We generalize the gauging of $ \mathbb{Z}_2$ symmetries by inserting Majorana fermions, establishing parallel duality correspondences for bosonic and fermionic lattice systems. Using this fermionic gauging, we construct fermionic analogs of $ \mathbb{Z}_2$ gauge theories dual to the transverse-field Ising model, interpretable as Majorana stabilizer codes. We demonstrate a unitary equivalence between the $ \mathbb{Z}_2$ gauge theory obtained by gauging the fermion parity of a free fermionic system and the conventional $ \mathbb{Z}_2$ gauge theory with potentially nonlocal terms on the square lattice with toroidal geometry. This equivalence is implemented by a linear-depth local unitary circuit, connecting the bosonic and fermionic toric codes through a direction-dependent anyonic transmutation. The gauge theory obtained by gauging fermion parity is further shown to be equivalent to a folded Ising chain obtained via the Jordan–Wigner transformation. We clarify the distinction between the recently proposed Kramers–Wannier dualities and those obtained by gauging the $ \mathbb{Z}_2$ symmetry along a space-covering path. Our results extend naturally to higher-dimensional $ \mathbb{Z}_2$ lattice gauge theories, providing a unified framework for bosonic and fermionic dualities and offering new insights for quantum computation and simulation.
Strongly Correlated Electrons (cond-mat.str-el), Statistical Mechanics (cond-mat.stat-mech), High Energy Physics - Lattice (hep-lat), Quantum Physics (quant-ph)
6+17 pages. This work is dedicated to C. N. Yang
The generic Mott transition in the sine-Gordon model through an embedded worm algorithm
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-10-27 20:00 EDT
Oscar Bouverot-Dupuis, Laura Foini, Alberto Rosso
The generic Mott transition in one-dimensional quantum systems can be described by the sine-Gordon model with a tilt via bosonization. Because the configuration space of the sine-Gordon model separates into distinct topological sectors, standard local Monte Carlo schemes are limited to very small system sizes. To overcome this limitation, we introduce the smooth worm (SmoWo) Monte Carlo algorithm which enlarges the configuration space to allow smooth transitions between topological sectors. The method combines worm updates with event-chain Monte Carlo moves. We explicitly prove its validity and quantify its performance. Thanks to the substantial acceleration achieved by the SmoWo algorithm, we are able to simulate large system sizes, providing a precise picture of the different phases and critical behaviour of the sine-Gordon model.
Strongly Correlated Electrons (cond-mat.str-el)
35 pages, 20 figures
Tensor-Network study of Ising model on infinite hyperbolic dodecahedral lattice
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-10-27 20:00 EDT
We propose a tensor-network-based algorithm to study the classical Ising model on an infinitely large hyperbolic lattice with a regular 3D tesselation of identical dodecahedra. We reformulate the corner transfer matrix renormalization group (CTMRG) algorithm from 2D to 3D to reproduce the known results on the cubic lattice. Consequently, we generalize the CTMRG to the hyperbolic dodecahedral lattice, which is an infinite-dimensional lattice. We analyze the spontaneous magnetization, von Neumann entropy, and correlation length to find a continuous non-critical phase transition on the dodecahedral lattice. The phase transition temperature is estimated to be $ T_{\rm pt} \approx 4.66$ . We find the magnetic critical exponents $ \beta= 0.4999$ and $ \delta=3.007$ that confirm the mean-field universality class in accord with predictions of Monte Carlo and high-temperature series expansions. The algorithm can be applied to arbitrary multi-state spin models.
Statistical Mechanics (cond-mat.stat-mech)
14 pages, 15 figures, 2 tables
Floating zone growth of high-purity MgO substrate single crystals
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-10-27 20:00 EDT
Christo Guguschev, Michael Schulze, Andrea Dittmar, Detlef Klimm, Kaspars Dadzis, Thomas Schroeder, Knut Peters, Aakash Pushp
MgO single crystals with diameters between 3.5 and 5 mm and lengths up to 40 mm were grown by the optical floating zone technique (OFZ). Despite challenging material properties such as the high melting point of 2825 °C, very high evaporation rate and perfect {100} cleaving characteristics, crack-free crystals were grown at high growth rates exceeding 40 mm/h and at high thermal gradients. Chemical investigations revealed that the OFZ technique is suitable for the preparation of substrate crystals with a purity of 5N to facilitate the development of novel demonstrator devices based on epitaxially grown thin films. The achieved purity level is improved by more than one order of magnitude if compared to commercial MgO substrate single crystals graded as high purity.
Materials Science (cond-mat.mtrl-sci)
Landau Polarons as Generators of Quantum-Coherent States
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-10-27 20:00 EDT
Arnab Ghosh, Patrick Brosseau, Dmitry N. Dirin, Rui Tao, Maksym V. Kovalenko, Patanjali Kambhampati
Since Landau’s theory, polarons have been understood as quasiparticles in which charges are dressed by the lattice field, yet decades of transport and spectroscopic studies have yielded only static indirect renormalizations. Whether such dressing can dynamically reorganize electronic spectra to generate new quantum-coherent states has remained unresolved. Here we use femtosecond coherent multidimensional spectroscopy on size and composition controlled perovskite quantum dots to track polaronic field-induced dynamics in real time, revealing their consequences. We observe a delayed condensation into a confined spectrum of coherent states on 50-150 fs timescales, with couplings between these states evolving dynamically on the same timescale. The splittings are robust, exhibit anomalous linear size dependence, exceed single-particle splittings and manifest at 300 K. A Raman-constrained spin-boson Hamiltonian captures both the anomalous scaling and dynamical onset, establishing polarons as generators of coherent manifolds that enable collective quantum phenomena including superradiance, superfluorescence and superabsorption.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Materials Science (cond-mat.mtrl-sci), Quantum Physics (quant-ph)
Elastic moduli of blue phases of cholesteric liquid crystals with low chirality
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-10-27 20:00 EDT
A new theoretical approach has been developed to describe the elastic properties of cubic blue phases of cholesteric liquid crystals (LCs). Blue phases are three-dimensional periodic chiral liquids with local anisotropy of the average orientation of molecules, and due to their periodicity, they have lattice elastic moduli characteristic of ordinary crystalline solids. The rigid tensor approximation, which works well at low chirality parameter ($ \kappa\ll1$ ), was used to calculate the elastic moduli of the experimentally observed blue phases $ O^8$ (BPI) and $ O^2$ (BPII). It is shown that in the one-constant approximation for Frank moduli of LCs ($ K_{11}=K_{22}=K_{33}$ ), the cubic lattice of blue phases has isotropic elasticity, and the Lamé’s first parameter $ \lambda_\mathrm{L}$ and Poisson’s ratio $ \nu$ are equal to zero. It is found that the sign of the Poisson’s ratio is determined by the ratio of elastic moduli $ K_0/K_1$ ; in particular, when $ K_0>K_1$ , the Poisson’s ratio is negative.
Soft Condensed Matter (cond-mat.soft)
12 pages, 4 figures
Photoinduced Metal-to-Insulator Transitions in 2D Moiré Devices
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-10-27 20:00 EDT
Yiliu Li, Esteban Rojas-Gatjens, Yinjie Guo, Birui Yang, Dihao Sun, Luke Holtzman, Juseung Oh, Katayun Barmak, Cory R. Dean, James C. Hone, Nathaniel Gabor, Eric A. Arsenault, Xiaoyang Zhu
Photoexcitation has been utilized to control quantum matter and to uncover metastable phases far from equilibrium. Among demonstrations to date, the most common is the photo-induced transition from correlated insulators to metallic states; however, the reverse process without initial orders has not been observed. Here, we show ultrafast metal-to-insulator transition in gate-doped WS2/WSe2 and WSe2/WSe2 moiré devices using photo-thermionic hole injection from graphite gates. The resulting correlated insulators are metastable, with lifetimes exceeding microseconds. These findings establish an effective mechanism for the ultrafast control of correlated electronic phases in van der Waals heterostructures.
Strongly Correlated Electrons (cond-mat.str-el)
13 pages, 4 figures, SI
Ultrafast Charge-Doping via Photo-Thermionic Injection in van der Waals Devices
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-10-27 20:00 EDT
Yiliu Li, Esteban Rojas-Gatjens, Yinjie Guo, Birui Yang, Dihao Sun, Luke Holtzman, Juseung Oh, Katayun Barmak, Cory R. Dean, James C. Hone, Nathaniel Gabor, Eric A. Arsenault, Xiaoyang Zhu
Van der Waals (vdW) heterostructures of two-dimensional (2D) materials have become a rich playground for the exploration of correlated quantum phases, and recent studies have begun to probe their non-equilibrium dynamics under femtosecond laser excitation. In a time-resolved experiment, optical excitation of the multilayer structure can lead not only to rich dynamic responses from the target layers, such as moiré interfaces, but also to additional device functionality from the layer degree of freedom. Here, we investigate optical excitation in a prototypical moiré device of dual-gated twisted WSe2 bilayers, with few-layer graphite gates and hexagonal boron nitride (hBN) spacers. We establish an ultrafast photodoping mechanism in the moiré bilayer from photo-thermionic emission of the graphite gates. Using transient reflectance experiments, we reveal photo-induced hole injection evidenced by: (i) a shift of gate voltages at which optical signatures of correlated insulators are observed, (ii) a persistent optical signature indicative of charge diffusion at microsecond timescales and local charge buildup from pulse-to-pulse accumulation, and (iii) photoinduced absorption due likely to transient formation of correlated insulators. We further demonstrate that the injected holes can be selectively controlled by tuning the excitation energy, fluence, and gate bias.
Strongly Correlated Electrons (cond-mat.str-el)
16 pages, 4 figures, SI
Characterizing Neon Thin Film Growth with an NbTiN Superconducting Resonator Array
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-10-27 20:00 EDT
Kyle Matkovic, Patrick Russell, Andrew Palmer, Eric Helgamo, Lukas Delventhal, Kun Zuo, Kundan Surse, Rajib Rahman, Maja C. Cassidy
Electrons levitating above the surface of solid neon have recently emerged as a promising platform for high-quality qubits. The morphology and uniformity of the neon growth in these systems is crucial for qubit performance in a scalable architecture. Here we report on the controlled growth and characterization of thin solid neon films using multiplexed superconducting microwave resonators. By monitoring changes in the resonant frequency and internal quality factor ($ Q_i$ ) of an array of frequency multiplexed quarter-wave coplanar waveguide resonators, we quantify the spatial uniformity of the film. A pulsed gas deposition protocol near the neon triple point results in repeatable film formation, generating measurable shifts in frequency and variations in $ Q_i$ across the resonator array. Notably, introducing a post-deposition anneal at 12 K for one hour improves the film homogeneity, as shown by the reduced resonator-to-resonator variance in frequency and $ Q_i$ , consistent with enhanced wetting. These results demonstrate resonator-based metrology as an in-situ tool for characterising neon film growth, directly supporting the development of electron on inert quantum solid qubit platforms.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Quantum Physics (quant-ph)
Chocolate suspensions as a model for jamming and nonlinear rheology
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-10-27 20:00 EDT
Michel Orsi, Veeraj Shah, Mahesh Padmanabhan, Thomas Curwen, Jeffrey F. Morris
We investigate the rheology of dark chocolate pastes in both industrially relevant pre-refined form and simplified model systems. Steady and oscillatory shear experiments reveal yielding, pronounced shear-thinning, and stress-dependent hysteresis governed by solid loading. Fitting the viscosity data with the Maron-Pierce model provides stress-dependent maximum flowable fractions $ \phi_{\rm{m}}(\sigma)$ , defining yield loci in the $ (\phi, \sigma)$ plane. Their variation with stress quantifies the coupled roles of friction and adhesion in setting flow limits. Large-amplitude oscillatory shear tests characterize transitions from elastic to viscous behavior and identify distinct recovery pathways near jamming. Contact-stress decomposition separates hydrodynamic and frictional contributions, confirming that adhesive contact networks dominate stress transmission in pre-refined pastes. These results establish chocolate pastes as dense, adhesive suspensions whose flow is controlled by the interplay of friction and adhesion, offering quantitative benchmarks for constitutive modeling and linking chocolate processing to the broader physics of constraint rheology.
Soft Condensed Matter (cond-mat.soft), Fluid Dynamics (physics.flu-dyn)
The spinterface mechanism for the chiral-induced spin selectivity effect: A Critical Perspective
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-10-27 20:00 EDT
Subhajit Sarkar, Amos Sharoni, Oliver L. A. Monti, Yonatan Dubi
The chiral-induced spin selectivity (CISS) effect, whereby chiral molecules preferentially transmit electrons of one spin orientation, remains one of the most intriguing and debated phenomena at the interface of spintronics, molecular electronics, and quantum materials. Despite extensive experimental observations across diverse platforms - including transport junctions, photoemission, and enantioselective chemistry - a comprehensive theoretical framework is still lacking. In this perspective, we critically examine the spinterface mechanism as a unifying explanation for the CISS effect. The spinterface model, which hypothesizes a feedback interaction between electron motion in chiral molecules and fluctuating surface magnetic moments, is shown to quantitatively reproduce experimental data across various systems and conditions. We contrast it with some existing theoretical models, highlighting key experimental features. Importantly, we also address open questions and criticisms of this model, including the nature of surface magnetism, the role of dissipation, and the applicability of the mechanism to non-helical or electrode-free systems. By offering falsifiable predictions and reconciling theory with experimental raw data, this work aims to sharpen the dialogue surrounding the microscopic origin of CISS and stimulate further experimental and theoretical progress.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Materials Science (cond-mat.mtrl-sci), Chemical Physics (physics.chem-ph), Quantum Physics (quant-ph)
Published online in ACS Nano on 21st October, 2025
The geometry and dynamics of annealed optimization in the coherent Ising machine with hidden and planted solutions
New Submission | Disordered Systems and Neural Networks (cond-mat.dis-nn) | 2025-10-27 20:00 EDT
Federico Ghimenti, Adithya Sriram, Atsushi Yamamura, Hideo Mabuchi, Surya Ganguli
The coherent Ising machine (CIM) is a nonconventional hardware architecture for finding approximate solutions to large-scale combinatorial optimization this http URL operates by annealing a laser gain parameter to adiabatically deform a high-dimensional energy landscape over a set of soft spins, going from a simple convex landscape to the more complex optimization landscape of interest. We address how the evolving energy landscapes guides the optimization dynamics against problems with hidden planted solutions. We study the Sherrington-Kirkpatrick spin-glass with ferromagnetic couplings that favor a hidden configuration by combining the replica method, random matrix theory, the Kac-Rice method and dynamical mean field theory. We characterize energy, number, location, and Hessian eigenspectra of global minima, local minima, and critical points as the landscape evolves. We find that low energy global minima develop soft-modes which the optimization dynamics can exploit to descend the energy landscape. Even when these global minima are aligned to the hidden configuration, there can be exponentially many higher energy local minima that are all unaligned with the hidden solution. Nevertheless, the annealed optimization dynamics can evade this cloud of unaligned high energy local minima and descend near to aligned lower energy global minima. Eventually, as the landscape is further annealed, these global minima become rigid, terminating any further optimization gains from annealing. We further consider a second optimization problem, the Wishart planted ensemble, which contains a hidden planted solution in a landscape with tunable ruggedness. We describe CIM phase transitions between recoverability and non-recoverability of the hidden solution. Overall, we find intriguing relations between high-dimensional geometry and dynamics in analog machines for combinatorial optimization.
Disordered Systems and Neural Networks (cond-mat.dis-nn), Statistical Mechanics (cond-mat.stat-mech), Optics (physics.optics)
Multistability of interstitial magnesium and its carrier recombined migration in gallium nitride
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-10-27 20:00 EDT
Yuansheng Zhao, Kenji Shiraishi, Tetsuo Narita, Atsushi Oshiyama
We present density-functional-theory calculations which provide a microscopic picture of the recombination-enhanced migration of interstitial Mg in GaN. We determine stable structures and migration pathways with accurate HSE approximation to the exchange-correlation energy, and also computed recombination rates using the obtained energy spectrum and wavefunctions. It is found that the migration between the most stable octahedral sites (Mg$ _{\textrm{O}}$ ) via newly found interstitial complex structure shows the lowest migration energy in which one or two electrons are captured during the migration, that the most stable charge state of 2+ changes to 1+ or neutral, and that by this recombination of carriers the migration barrier is significantly reduced. Starting from Mg$ _{\textrm{O}}^{2+}$ , Mg captures an electron becoming the 1+ charge state and overcomes the barrier of 1.65 eV, much reduced from 2.23 eV in case of the migration with the 2+ charge state kept. Moreover, further electron capture is realized accompanied by substantial structural relaxation, thus Mg becoming neutral. Detailed HSE calculations for this second capture show that the migration barrier is 1.55 eV, thus clarifying the important role of the carrier recombination for Mg migration in GaN. These findings are corroborated by the present quantitative calculations of recombination rates based on electronic Hamiltonian constructed from our DFT-obtained energy spectrum. The timescale of the recombination is clarified to be in or under the timescale of the migration with typical electron density and the enhancement is expected to be significant.
Materials Science (cond-mat.mtrl-sci)
Paramagnetic electron-nuclear spin entanglement in HoCo2Zn20
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-10-27 20:00 EDT
Takafumi Kitazawa, Yasuyuki Shimura, Takahiro Onimaru, Shun Tsuchida, Katsunori Kubo, Yoshinori Haga, Hironori Sakai, Yoshifumi Tokiwa, Shinsaku Kambe, Yo Tokunaga
We investigated electron-nuclear spin entanglement in the paramagnetic ground state of the Ho-based cubic compound HoCo2Zn20. From analyses of magnetization and specific heat data, we determined the cubic crystalline electric field (CEF) parameters, the magnetic exchange constant, and the hyperfine coupling constant between the 4f magnetic moment and the 165Ho nuclear spin. Our results show that the Gamma5 CEF ground state is split by the hyperfine coupling, with an energy width of 1.3 K at 0 T, and that the true paramagnetic ground state is a quasi-sextet arising primarily from entanglement between the f-electron effective spin S = 1 and the 165Ho nuclear spin I = 7/2. We further demonstrate that, depending on the CEF parameters, the paramagnetic ground state can switch to an electron-nuclear coupled dectet. These findings underscore the importance of accurately identifying the electron-nuclear level scheme for understanding the low-temperature properties of rare-earth compounds containing spin-active nuclei.
Strongly Correlated Electrons (cond-mat.str-el)
15 pages, 11 figures
One-dimensional moiré engineering in zigzag graphene nanoribbons on hBN
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-10-27 20:00 EDT
Ryosuke Okumura, Naoto Nakatsuji, Takuto Kawakami, Mikito Koshino
We study the structural relaxation and electronic properties of a one-dimensional (1D) moiré system composed of a zigzag graphene nanoribbon (GNR) placed on a hexagonal boron nitride (hBN) substrate. Using an effective grid model derived from continuum elasticity theory, we calculate the relaxed atomic structure of the GNR/hBN system for various twist angles and ribbon widths. The relaxation gives rise to a characteristic 1D domain structure consisting of alternating commensurate AB$ ‘$ regions and two distinct types of domain boundaries. At finite twist angles, the ribbon adopts a wavy shape, locally tracing the hBN zigzag direction but occasionally sliding to adjacent atomic rows. The resulting moiré potential strongly modulates the electronic structure: the zero-energy zigzag edge states are modulated by the local stacking, leading to densely packed subbands in the AB$ ‘$ domains and sharply localized domain-wall states in the energy gaps between domain plateaus, which together realize gate-tunable one-dimensional arrays of quantum-confined electronic states. Our results demonstrate that moiré modulation in GNR/hBN heterostructures provides a versatile platform for electronic structure engineering and the design of 1D moiré nanodevices.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
13 pages, 8 figures
Versatile tunable optical injection of chiral polarized Weyl fermions in a magnetic Weyl semimetal Co3Sn2S2
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-10-27 20:00 EDT
Zipu Fan, Junchao Ma, Jinying Yang, Yan Sun, Zhuocheng Lu, Shuxia Chen, Delang Liang, Dehong Yang, Chang Xu, Qinsheng Wang, Anlian Pan, Ji Feng, Enke Liu, JinLuo Cheng, Dong Sun
Precise probe and control of various quantum degrees of freedom in novel quantum matter are central to understanding fundamental quantum physics and hold promise for innovative routes to encode and process information. Chirality is one such degree of freedom that has recently attracted intense research interest, especially for Weyl fermions in topological Weyl semimetals. The coupling of chiral degrees of freedom through light-matter interactions and the versatile control of these couplings through external fields can lead to precise quantum control of Weyl fermions. In this work, we demonstrate the observation of light chirality-dependent photocurrent in the mid-infrared regime. Excitation wavelength-dependent measurements reveal that the photocurrent originates from the injection of chiral polarized Weyl fermions by chiral polarized mid-infrared photons. The optical process that generates unbalanced chiral polarized Weyl fermions is determined to be a third-order nonlinear photocurrent process. Compared with nonmagnetic Weyl semimetals, such coupling is versatilely tunable in magnetic Weyl semimetals with the magnetization direction and external electric field in addition to the chirality of light. Our results are not only directly applicable to tunable circular-polarization-sensitive photodetection in the mid-infrared regime, but also pave the way toward functional quantum devices that utilize the chiral quantum degrees of freedom of Weyl fermions.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Unveiling the BEC-droplet transition with Rayleigh superradiant scattering
New Submission | Quantum Gases (cond-mat.quant-gas) | 2025-10-27 20:00 EDT
Mithilesh K. Parit, Mingchen Huang, Ziting Chen, Yifei He, Haoting Zhen, Gyu-Boong Jo
Light scattering plays an essential role in uncovering the properties of quantum states through light-matter interactions. Here, we explore the transition from Bose-Einstein condensate (BEC) to droplets in a dipolar $ ^{166}$ Er gas by employing superradiant light scattering as both a probing and controlling tool. We observe that the efficiency of superradiant scattering exhibits a non-monotonic behavior akin to the rate of sample expansion during the transition, signaling its sensitivity to the initial quantum state, and in turn, revealing the BEC-droplet transition. Through controlled atom depletion via superradiance, we analyze the sample’s expansion dynamics and aspect ratio to identify the BEC-droplet phases distinctly, supported by Gaussian variational ansatz calculations. Finally, using these two approaches, we track how the BEC-droplet transition points shift under varying magnetic field orientations. Our work opens new avenues for studying quantum states through superradiance, advancing our understanding of both the BEC-droplet crossover and its coherence properties.
Quantum Gases (cond-mat.quant-gas), Quantum Physics (quant-ph)
6 pages, 4 figures, supplementary notes
Temperature-Dependent Spectroscopy of Cr3+:YGG Nanophosphors with Multisite Emission
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-10-27 20:00 EDT
An important feature of Cr3+ is the ability to tune the absorption and emission spectra by changing the host. However, in some cases, different emission spectra can be detected in samples with similar Racah parameters. The present paper reports changes in the luminescence properties of Cr3+:YGG nanocrystals. Cr3+:YGG nanocrystals were synthesized by a modified Pechini method to obtain nanocrystals containing two fractions of Cr3+:YGG nanocrystals with different lattice parameters and crystalline sizes. The increase in the concentration of Cr3+ ions leads to a redshift of the 4T2g emission from 750 nm to 850 nm for luminescence spectra measured at 80K. In contrast, room temperature luminescence spectra showed similarity in the shape of the emission spectra. The calculated crystal field strength was found to increase with the concentration of Cr3+ ions, so the detected patterns in low-temperature luminescence spectra were explained by energy transfer chain processes.
Materials Science (cond-mat.mtrl-sci)
Chaika, M. (2025). Temperature-Dependent Spectroscopy of Cr3+: YGG Nanophosphors with Multisite Emission. Materials Research Bulletin, 113841
Optimal spin-charge interconversion in graphene through spin-pseudospin entanglement control
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-10-27 20:00 EDT
Joaquín Medina Dueñas, Santiago Giménez de Castro, Jose H. Garcia, Stephan Roche
The electrical generation of spin signals is of central interest for spintronics, where graphene stands as a relevant platform as its spin-orbit coupling (SOC) is tuned by proximity effects. Here, we propose an enhancement of spin-charge interconversion in graphene by controlling the intraparticle entanglement between the spin and pseudospin degrees of freedom. We demonstrate that, although the spin alone is not conserved in Rashba-Dirac systems, a combined spin-pseudospin operator is conserved. This conserved quantity represents the interconversion between pure spin and pseudospin textures to a spin-pseudospin entangled structure, where Kane-Mele SOC tunes this balance. By these means, we achieve spin-charge interconversion of 100% efficiency via the Rashba-Edelstein effect. Quantum transport simulations in disordered micron-size systems demonstrate the robustness of this effect, and also reveal a disorder resilient spin Hall effect generated by the interplay between Rashba and Kane-Mele SOC. Our findings propose a platform for maximally efficient spin-charge interconversion, and establish spin-pseudospin correlations as a mechanism to tailor spintronic devices.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Materials Science (cond-mat.mtrl-sci), Computational Physics (physics.comp-ph)
Toward more performant eye safe lasers: effect of increasing sensitizer amount in Yb3+,Er3+:YAG transparent ceramic on its spectral characteristics
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-10-27 20:00 EDT
Agnieszka Szysiak, Robert Tomala, Helena Węglarz, Juraj Kajan, Mirosław Słobodzian, Mykhailo Chaika
Developing efficient Er3+,Yb3+:YAG eye-safe lasers is a priority of modern laser technology. This paper focuses on the influence of the concentration of Yb3+ ions on the spectroscopic properties of Er3+,Yb3+:YAG transparent ceramics. Four samples with different concentrations of Yb3+ ions were prepared by solid-state reaction sintering. The study revealed the influence of Yb3+ ions on the microstructure and the sintering process. A high concentration of Yb3+ ions leads to the formation of Y3+-rich impurity phases and causes segregation of Er3+ and Yb3+ and Si4+ into these phases. The influence of Yb3+ ions on the shape of emission spectra and the lifetimes of both Er3+ and Yb3+ ions was shown. Changes in the spectroscopic properties were ascribed to increase in neat transfer between Yb3+ and Er3+ ions. IQE of Er3+ and Yb3+ luminescence were calculated, and optimal Er3+/Yb3+ ions ratio were proposed
Materials Science (cond-mat.mtrl-sci)
Szysiak, A., e.all (2025). Toward more performant eye safe lasers: Effect of increasing sensitizer amount in Yb3+, Er3+: YAG transparent ceramic on its spectral characteristics. Journal of the European Ceramic Society, 45(11), 117365
Tracer Diffusion in Granular Suspensions: Testing the Enskog Kinetic Theory with DSMC and Molecular Dynamics
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-10-27 20:00 EDT
Antonio M. Puertas, Rubén Gómez González
We investigate the diffusion of an intruder in a granular gas, with both components modeled as smooth hard spheres, both immersed in a low viscosity carrier fluid to form a particle-laden suspension. In this system, dissipative particle collisions coexist with the action of a solvent. The latter is modeled via a viscous drag force and a stochastic Langevin-like force proportional to the background fluid temperature. Building on previous kinetic theory and random-walk results of the tracer diffusion coefficient [R. Gómez González, E. Abad, S. Bravo Yuste, and V. Garzó, Phys. Rev. E \textbf{108}, 024903 (2023)], where random-walk predictions were compared with Chapman–Enskog results up to the second Sonine approximation, we assess the robustness of the Enskog framework by incorporating molecular dynamics (MD) simulations, using direct simulation Monte Carlo (DSMC) results as an intermediate reference. In particular, we focus on the intruder velocity autocorrelation function, considering intruders different masses (from 0.01 to 100 times the mass of the granular particles), and analyse the behavior of the intruder temperature and diffusion coefficient. Our results clarify the influence of the friction parameter and the conditions under which Enskog kinetic theory reliably describes intruder diffusion in granular suspensions.
Soft Condensed Matter (cond-mat.soft)
18 pages, 10 figures
Relativistic spin-Hall effect in an external magnetic field in Al and Pt
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-10-27 20:00 EDT
Yu.N. Chiang (Tszyan), M.O. Dzyuba
The relativistic Rashba contribution to the spin-Hall effect in external electric and magnetic fields in Al and Pt was investigated. Schemes of edge accumulation of spins are proposed that take into account the flip of spins when they do not coincide with the direction of the magnetic field. Based on the obtained experimental data on the spin-Hall effect, an assessment of the spin-orbit interaction in the studied paramagnets was made.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Tensor Renormalization-Group study of the surface critical behavior of a frustrated two-layer Ising model
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-10-27 20:00 EDT
Christophe Chatelain (LPCT)
Two replicas of a 2D Ising model are coupled by frustrated spin-spin interactions. It is known that this inter-layer coupling is marginal and that the bulk critical behavior belongs to the Ashkin-Teller (AT) universality class, as the $ J_1$ -$ J_2$ Ising model. In this work, the surface critical behavior is studied numerically by Tensor Renormalization-Group calculations. The Bond-Weight Tensor Renormalization Group algorithm is extended to tackle systems with boundaries. It is observed that the two-fold degeneracy of the surface magnetic scaling dimension of the AT model is lifted in the frustrated two-layer Ising model (F2LIM). The splitting is explained by the breaking of the $ {\mathbb Z}_2$ -symmetry under spin reversal of a single Ising replica in the F2LIM. The two distinct surface magnetic scaling dimensions $ x_1^s$ and $ x_2^s$ of the F2LIM satisfies a simple duality relation $ x_1^s=1/4x_2^s$ .
Statistical Mechanics (cond-mat.stat-mech)
Altermagnetism in an interacting model of Kagome materials
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-10-27 20:00 EDT
Alejandro Blanco Peces, Jaime Merino
The Hubbard model on the Kagome lattice is a widely used interacting model for describing the electronic properties of various transition metal-based Kagome materials. We find altermagnetism driven by Coulomb interaction in the Kagome Hubbard model at Dirac filling with no spin-orbit coupling nor explicit spatial symmetry breaking present. We show how this insulating altermagnet is relevant to other lattices with larger unit cells such as the Lieb-Kagome lattice. The ALM found displays a characteristic magnon splitting which can be detected in inelastic neutron scattering experiments on interacting Kagome materials.
Strongly Correlated Electrons (cond-mat.str-el)
7 pages, 4 figures, + Supplementary Material (7 pages, 5 figures)
Controlling bubble and skyrmion lattice order and dynamics via stripe domain engineering in ferrimagnetic Fe/Gd multilayers
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-10-27 20:00 EDT
Tim Titze (1), Sabri Koraltan (2,3), Timo Schmidt (4), Mailin Matthies (1), Amalio Fernández-Pacheco (2), Dieter Suess (3), Manfred Albrecht (4), Stefan Mathias (1,5), Daniel Steil (1) ((1) I. Physikalisches Institut, Universität Göttingen, Göttingen, Germany, (2) Institute of Applied Physics, TU Wien, Vienna, Austria, (3) Physics of Functional Materials, Faculty of Physics, University of Vienna, Austria, (4) Institute of Physics, University of Augsburg, Augsburg, Germany, (5) International Center for Advanced Studies of Energy Conversion (ICASEC), Universität Göttingen, Göttingen, Germany)
Ferrimagnetic Fe/Gd multilayers host maze-like stripe domains that transform into a disordered bubble/skyrmion lattice under out-of-plane magnetic fields at ambient temperature. Femtosecond magneto-optics distinguishes these textures via their distinct coherent breathing dynamics. Crucially, applying a brief in-plane ``set’’ magnetic field to the stripe state enhances both frequency and amplitude of the bubble/skyrmion lattice breathing mode. Lorentz transmission electron microscopy, magnetic force microscopy, and micromagnetic simulations reveal that this enhancement arises from field-aligned stripes nucleating a dense, near-hexagonal bubble/skyrmion lattice upon out-of-plane field application, with strong indications for a pure skyrmion lattice. Thus, modifying the initial domain configuration by in-plane fields enables precise control of coherent magnetization dynamics on picosecond to nanosecond timescales and potentially even of topology.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Materials Science (cond-mat.mtrl-sci)
8 pages, 7 figures
Faradaic and capacitive charging of an electrolyte-filled pore in response to a small applied potential
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-10-27 20:00 EDT
Timur Aslyamov, Massimiliano Esposito, Mathijs Janssen
Electrochemical devices often charge both through Faradaic reactions and electric double layer formation. Here, we study these coupled processes in a model system of a long electrolyte-filled pore subject to a small suddenly-applied potential, close to the equilibrium potential $ \Psi^\text{eq}$ at which there is no net Faradaic charge transfer. Specifically, we solve the coupled Poisson-Nernst-Planck and Frumkin-Butler-Volmer equations by asymptotic approximations, using the pore’s small inverse aspect ratio as the small parameter. In the early-time limit, the reaction-diffusion equations yield an extended Faradaic transmission line model that includes a voltage source, $ \Psi_\text{eq}$ , biasing the Faradaic reactions, captured by the resistance $ R_F$ . In the long-time limit, the model exhibits a nontrivial potential of zero charge, $ \Psi_\text{pzc} = \Psi_\text{eq}[1 - \hat{Z}(0)/R_F]$ , where $ \hat{Z}(0)$ is the experimentally accessible zero-frequency impedance of the system. This expression provides a new means to experimentally measure the Faradaic contribution to $ \Psi_\text{pzc}$ .
Statistical Mechanics (cond-mat.stat-mech), Soft Condensed Matter (cond-mat.soft), Chemical Physics (physics.chem-ph)
15 pages, 5 figures
High Pressure Superconducting transition in Dihydride BiH$_2$ with Bismuth Open-Channel Framework
New Submission | Superconductivity (cond-mat.supr-con) | 2025-10-27 20:00 EDT
Liang Ma, Xin Yang, Mei Li, Pengfei Shan, Ziyi Liu, Jun Hou, Sheng Jiang, Lili Zhang, Chuanlong Lin, Pengtao Yang, Bosen Wang, Jianping Sun, Yang Ding, Huiyang Gou, Haizhong Guo, Jinguang Cheng
Metal hydrides MHx with low hydrogen content are not expected to show high-Tc superconductivity owing to the low hydrogen-derived electronic density of states at Fermi level and the limited hydrogen contribution to electron-phonon coupling strength. In this work, we report on the successful synthesis of a novel bismuth dihydride superconductor, Cmcm-BiH$ _2$ , at approximately 150 GPa, and the discovery of superconductivity with Tc about 62 K at 163 GPa, marking the first instance of superconductor among the MH$ _2$ -type metal dihydrides. Cmcm-BiH$ _2$ adopts a unique host-guest type structure, in which the Bi atoms via weak Bi-Bi covalent bonds form a three-dimensional open-channel framework that encapsulates H$ _2$ -like molecules as guests, thereby broadening the structural diversity of hydrides under high pressures. The occurrence of superconductivity is evidenced by a sharp drop of resistivity to zero and the characteristic downward shift of Tc under applied magnetic fields. Notably, Cmcm-BiH$ _2$ remains stable down to at least 97 GPa during decompression, with the calculated lowest pressure for dynamic stability of 10 GPa. In-depth analysis reveals that the covalent bismuth open-channel structure forms metallic conduction channels, dominates the electronic states near the Fermi level, and contributes approximately 51% of the total $ lambda$ in Cmcm-BiH$ _2$ , distinguishing it from known high-pressure hydride superconductors. These findings highlight the critical role of non-hydrogen elements in producing superconductivity and open new avenues for the design and optimization of high-Tc hydride superconductors.
Superconductivity (cond-mat.supr-con)
Koopman Mode Decomposition of Thermodynamic Dissipation in Nonlinear Langevin Dynamics
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-10-27 20:00 EDT
Daiki Sekizawa, Sosuke Ito, Masafumi Oizumi
Nonlinear oscillations are commonly observed in complex systems far from equilibrium, such as living organisms. These oscillations are essential for sustaining vital processes, like neuronal firing, circadian rhythms, and heartbeats. In such systems, thermodynamic dissipation is necessary to maintain oscillations against noise. However, due to their nonlinear dynamics, it has been challenging to determine how the characteristics of oscillations, such as frequency, amplitude, and coherent patterns across elements, influence dissipation. To resolve this issue, we employ Koopman mode decomposition, which recasts nonlinear dynamics as a linear evolution in a function space. This linearization allows the dynamics to be decomposed into temporal oscillatory modes coherent across elements, with the Koopman eigenvalues determining their frequencies. Using this method, we decompose thermodynamic dissipation caused by nonconservative forces into contributions from oscillatory modes in overdamped nonlinear Langevin dynamics. We show that the dissipation from each mode is proportional to its frequency squared and its intensity, providing an interpretable, mode-by-mode picture. In the noisy FitzHugh–Nagumo model, we demonstrate the effectiveness of this framework in quantifying the impact of oscillatory modes on dissipation during nonlinear phenomena like stochastic resonance and bifurcation. For instance, our analysis of stochastic resonance reveals that the greatest dissipation at the optimal noise intensity is supported by a broad spectrum of frequencies, whereas at non-optimal noise levels, dissipation is dominated by specific frequency modes. Our work offers a general approach to connecting oscillations to dissipation in noisy environments and improves our understanding of diverse oscillation phenomena from a nonequilibrium thermodynamic perspective.
Statistical Mechanics (cond-mat.stat-mech)
Strain-induced structural change and nearly-commensurate diffuse scattering in the model high-temperature superconductor HgBa$2$CuO${4+δ}$
New Submission | Superconductivity (cond-mat.supr-con) | 2025-10-27 20:00 EDT
Mai Ye, Wenshan Hong, Tom Lacmann, Mehdi Frachet, Igor Vinograd, Gaston Garbarino, Sofia-Michaela Souliou, Michael Merz, Rolf Heid, Amir-Abbas Haghighirad, Yuan Li, Matthieu Le Tacon
We investigate the strain response of underdoped HgBa$ 2$ CuO$ {4+\delta}$ (Hg1201), by synchrotron X-ray diffraction and corresponding simulations of thermal diffuse scattering. The compression in the crystallographic $ a$ direction leads to relatively small expansion in the $ b$ and $ c$ directions, with Poisson ratios $ \nu{ba}$ =0.16 and $ \nu{ca}$ =0.11, respectively. However, the Cu-O distance in the $ c$ direction exhibits a notable 0.9% increase at 1.1% $ a$ -axis compression. We further find strain-induced diffuse scattering which corresponds to a new type of two-dimensional charge correlation. Interestingly, this signal is insensitive to the onset of superconductivity and instead corresponds to a short-range, nearly commensurate modulation with a wave vector close to (0.5, 0, 0) and a correlation length of approximately four unit cells. It closely resembles the charge order theoretically predicted in the phase diagram of the spin-liquid model with resonating valence bonds on a square lattice.
Superconductivity (cond-mat.supr-con)
Universal Thickness-Dependent Absorption in Solids at the Nanoscale
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-10-27 20:00 EDT
Bhumika Chauhan, Nikhil Singh, Subhrajit Dalai, Abhisek Saidarsan, Sayantan Patra, Sourabh Jain, Aparna Deshpande, Ashish Arora
Through systematic experimental and theoretical studies of layer-thickness-dependent absorption in semiconducting MoSe$ _2$ and WS$ _2$ across the visible to near-infrared spectral range, we demonstrate a universal absorption behavior in solids at nanoscale thicknesses. With increasing thickness, a non-monotonic evolution of absorption integrated over the measured spectral region is revealed which is accompanied by pronounced oscillatory features. This strongly deviates from the expected Beer-Lambert law. The observed behavior has origins in the electromagnetic interference effects taking place between the two surfaces of the thin crystals. The present work on 2D semiconductors is extendable to all kinds of solids such as conventional semiconductors (e.g. Si, GaAs, GaN, InP), (semi)metals (e.g. Al, Ag, Au, c-HOPG) and 2D magnetic materials (e.g. CrSBr and NiPS$ _3$ ). Our results provide fundamental insights into light-matter interactions in solids at the nanoscale and are vital for optimally designing the new generation of absorption-based flexible optoelectronic devices.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Optics (physics.optics)
11 pages, 4 figures in main text, 12 figures in supplementary materials
Lossy phononic metamaterials for valley manipulation
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-10-27 20:00 EDT
Shunda Yin, Qiuyan Zhou, Yuxiang Xi, Weiyin Deng, Wei Chen, Jiuyang Lu, Manzhu Ke, Zhengyou Liu
Non-Hermitian physics characterized by complex band spectra has established a new paradigm in condensed matter systems and metamaterials. Recently, non-Hermitian gain and nonreciprocity are deliberately introduced to valley manipulation, leading to various phenomena beyond the Hermitian scenarios, such as the amplified topological whispering gallery modes as an acoustic laser. In contrast, pure loss is inevitable in practice and generally regarded as a detrimental factor. Here, we reveal that the coupling loss can manipulate valley degrees of freedom in a phononic metamaterial. Three distinct valley-related effects, including valley-resolved nonreciprocity that functions as a valley filter, valley-dependent skin effects where bulk states from different valleys localize at opposite boundaries, and valley-projected edge states with boundary-dependent lifetimes that leads to an anomalous beam splitting, are demonstrated through theoretical analysis and airborne sound experiments. Owing to the easy preparation of loss, our findings shed light on both non-Hermitian and valley physics and may facilitate innovative applications of valley-related devices.
Materials Science (cond-mat.mtrl-sci)
18 pages,4 figures
Suppressing excitations using quantum-Brachistochrone and nearest-neighbour interactions
New Submission | Other Condensed Matter (cond-mat.other) | 2025-10-27 20:00 EDT
S John Sharon Sandeep, Dibyajyoti Sahu, Suhas Gangadharaiah
We examine excitation suppression in the transverse-field Ising model (TFIM), where finite-time drive across a quantum critical point is assisted by the presence of a time-dependent coupling parameter. While conventional counterdiabatic protocols are designed to eliminate excitations, they often require complex many-body terms that are difficult to realize experimentally. In contrast, our approach employs a local, time-dependent modulation of an existing coupling term in the Hamiltonian. Within the framework of quantum optimal control, we find that under a linear ramp of the transverse field, the optimal evolution of the second parameter follows a non-monotonic trajectory. For the TFIM, this protocol yields higher fidelity and improved robustness against noise compared to several orders of approximate counterdiabatic driving. Furthermore, we provide an analytical demonstration of anti-Kibble-Zurek scaling in the presence of noise acting on either the transverse field or the longitudinal coupling. These results highlight the potential of this approach for developing simple, noise-resilient protocols for finite-time quantum state preparation.
Other Condensed Matter (cond-mat.other), Quantum Physics (quant-ph)
15 pages, 10 figures
Optimal superconductivity in twisted bilayer WSe$_2$ where the Van Hove singularity crosses half-filling
New Submission | Superconductivity (cond-mat.supr-con) | 2025-10-27 20:00 EDT
Michał Zegrodnik, Waseem Akbar, Andrzej Biborski, Louk Rademaker
The recent discovery of unconventional superconductivity has pointed to twisted WSe$ _2$ bilayer as a versatile platform for studying the correlated and topological phases of matter. Here we analyze the effect of the displacement field and electron interactions on the formation of a topological paired state in twisted WSe$ _2$ . Our approach is based on the effective single band $ t$ -$ J$ -$ U$ model supplemented with intersite Coulomb interaction term and treated within the Gutzwiller approximation. We show that the superconducting phase is stabilized in a small range of displacement fields where the Van Hove singularity crosses half-filling, which is in qualitative agreement with recent experimental data. According to our analysis, such a circumstance comes as a result of a subtle interplay between the large density of states of the Van Hove singularity, in combination with the renormalization effects that appear in the weak-to-moderate correlations regime. The two factors create favorable conditions for the SC pairing only in a small area of the phase diagram.
Superconductivity (cond-mat.supr-con), Strongly Correlated Electrons (cond-mat.str-el)
Spin filtering on demand via localized states in an atomic-scale resonant tunneling magnetic tunnel junction
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-10-27 20:00 EDT
Maciej Bazarnik, Anika Schlenhoff
Spin filtering and its back-action spin transfer torque (STT) are key ingredients of latest spintronic devices based on magnetic tunnel junctions (MTJs). Resonant tunneling (RT), implemented by design or occurring as parasitic effects, is known to crucially affect macroscopic device performance, but direct experimental access to its individual microscopic processes has remained difficult. Here we apply the RT scheme from MTJs to spin-polarized scanning tunneling microscopy (SP-STM) for ultimate miniaturization obtained by addressing distinct sites on individual nanomagnets. Combined with energy selectivity, our experimental model set-up enables to study the spin filtering capabilities of RT through an individual spin-split vacuum resonance state and of the corresponding STT exerted on the nanomagnet. We find, that the sign and magnitude of the STT follow the effective spin-polarization of the resonance state, which, as we show, can by tailored on demand either by adjusting the applied bias or the current injection point on the nanostructure. We anticipate, that our atomic-scale RT-MTJ approach and the discovery of a versatile tunable spin-filter at smallest scale will prove invaluable for studying and designing next generation MTJs potentially based on recently discovered 2D van-der-Waals magnets or altermagnets.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Applied Physics (physics.app-ph)
2D Excitonics with Atomically Thin Lateral Heterostructures
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-10-27 20:00 EDT
S. Shradha, R. Rosati, H. Lamsaadi, J. Picker, I. Paradisanos, Md T. Hossain, L. Krelle, L. F. Oswald, N. Engel, D. I. Markina, K. Watanabe, T. Taniguchi, P. K. Sahoo, L. Lombez, X. Marie, P. Renucci, V. Paillard, J.-M. Poumirol, A. Turchanin, E. Malic, B. Urbaszek
Semiconducting transition metal dichalcogenides (TMDs), such as MoSe$ _2$ and WSe$ _2$ , exhibit unique optical and electronic properties. Vertical stacking of layers of one or more TMDs, to create heterostructures, has expanded the fields of moiré physics and twistronics. Bottom-up fabrication techniques, such as chemical vapor deposition, have advanced the creation of heterostructures beyond what was possible with mechanical exfoliation and stacking. These techniques now enable the fabrication of lateral heterostructures, where two or more monolayers are covalently bonded in the plane of their atoms. At their atomically sharp interfaces, lateral heterostructures exhibit additional phenomena, such as the formation of charge-transfer excitons, in which the electron and hole reside on opposite sides of the interface. Due to the energy landscape created by differences in the band structures of the constituent materials, unique effects such as unidirectional exciton transport and excitonic lensing can be observed in lateral heterostructures. This review outlines recent progress in exciton dynamics and spectroscopy of TMD-based lateral heterostructures and offers an outlook on future developments in excitonics in this promising system.
Materials Science (cond-mat.mtrl-sci)
16 pages, 9 figures
An Experimental Validation of Reconfigurable Intelligent Surfaces Achieving Pulse Width-Modulated Singular Reflection Angles Without External Power Sources
New Submission | Other Condensed Matter (cond-mat.other) | 2025-10-27 20:00 EDT
Eisuke Omori, Kairi Takimoto, Atsuko Nagata, Ashif Fathnan, Shinya Sugiura, Hiroki Wakatsuchi
In this study, we introduce a design concept that leverages pulse width variation to enable a reconfigurable intelligent surface (RIS) and to autonomously switch reflection properties between two angles without any active control system. Our RIS alters its beam pattern from a singular specular reflection to another unique singular anomalous reflection when the incoming waveform changes from a short pulse to a continuous wave, even at the same frequency. Unlike conventional RISs, our passive control mechanism eliminates the requirements of active components and precise symbol-level synchronization with the transmitting antennas, reducing the system complexity level while offering dynamic material adaptability. We numerically show that the proposed RIS design is capable of varying the received magnitude of an incident wave by a factor of ten, which is also experimentally validated for the first time. Employing binary phase-shift keying (BPSK) modulation, we further report that the communication characteristics can be varied by 7 dB or more, which indicates that the proposed design is not limited to a single frequency component as long as the bandwidth of the given signal is covered by that of the RIS design. These results may present new opportunities for exploring and deploying pulse width-dependent RISs in practical scenarios involving next-generation communication systems.
Other Condensed Matter (cond-mat.other)
11 pages, 12 figures
Probing and modeling cell-cell communication in 2D biomimetic tissues
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-10-27 20:00 EDT
Cécile Marie Vincent, Sapna Ravindran, Alexis Michel Prevost, Léa-Laetitia Pontani, Olivier Bénichou, Elie Wandersman
In tissues, cells in direct physical contact with each other can exchange ions or molecules via protein clusters called gap junctions that form channels across the membranes of adjacent cells. Here, we use a simplified biomimetic approach, coupled with theoretical modeling, to unravel the physical mechanisms controlling such transport. Tissues are mimicked with 2D hexagonal networks of monodisperse aqueous droplets connected by lipid membranes called Droplet Interface Bilayers (DIBs), decorated with $ \alpha$ -Hemolysin ($ \alpha$ HL) transmembrane proteins forming nanopores through heptamerization in the membrane. The diffusion of calcein across 2D DIB networks is thoroughly studied using epifluorescence microscopy at various $ \alpha$ HL concentrations. The results are successfully confronted with a Continuous Time Random Walk model in hexagonal networks, with an average waiting time increasing nonlinearly with the concentration of pore monomers.
Soft Condensed Matter (cond-mat.soft), Biological Physics (physics.bio-ph)
8 pages, 5 figures
Examining the Spin Structure of Altermagnetic Candidate MnTe Grown with Near Ideal Stoichiometry
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-10-27 20:00 EDT
Qihua Zhang, Christopher J. Jensen, Alexander J. Grutter, Sandra Santhosh, William D. Ratcliff, Julie A. Borchers, Thomas W. Heitmann, Narendirakumar Narayanan, Timothy R. Charlton, Mingyu Yu, Ke Wang, Wesley Auker, Nitin Samarth, Stephanie Law
Altermagnets are a recently-discovered class of materials with magnetic ordering that have a zero net magnetization and a momentum-dependent spin splitting in their band structure, arising from a collinear spin arrangement with alternating polarizations in the crystal lattice. The nickeline-structured manganese telluride ({\alpha}-MnTe) is an attractive altermagnet candidate due to its predicted large spin splitting energy and a transition temperature near 300K. In this work, we present a thorough investigation of the spin structure of {\alpha}-MnTe thin films grown by molecular beam epitaxy with very high crystal quality and low residual magnetization. The epitaxial {\alpha}-MnTe films have a full-width-at-half-maximum of 0.1° as measured by x-ray-diffraction rocking curves and a root-mean-square roughness below 1 nm. Neutron diffraction measurements confirm the antiferromagnetic order in the {\alpha}-MnTe film and show a Néel temperature of 307 K. Polarized neutron reflectometry detects a vanishingly small net magnetization which may be confined to the MnTe/InP interface, highlighting the near-ideal stoichiometry in the sample. In vacuo angle resolved photoemission spectroscopy reveals that the bulk band spectrum of the MnTe films is consistent with the weak altermagnetic order as theoretically predicted and observed for the high symmetry nodal plane in the center of the Brillouin zone. This study establishes optimized growth conditions for the synthesis of stoichiometric {\alpha}-MnTe thin films which exhibit exceptional structural and magnetic ordering, thereby providing a robust platform for the precise characterization of their altermagnetic properties.
Materials Science (cond-mat.mtrl-sci)
Exciton-based sensing of remote electron correlations in 2D heterostructures
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-10-27 20:00 EDT
Tobias M. R. Wolf, Tian Xie, Chenhao Jin, Allan H. MacDonald
Many monolayer transition metal dichalcogenides, including MoS$ _2$ , MoSe$ _2$ , WS$ _2$ , and WSe$ _2$ , are direct bandgap two-dimensional (2D) semiconductors with sharp optical resonances at excitonic bound state frequencies. Recent experiments have demonstrated that excitonic resonance frequencies in multilayer van der Waals stacks are altered by long-range Coulomb interactions with electrons in nearby but electrically isolated 2D materials. These modulations have been successfully used to detect transitions between distinct states of remote strongly correlated 2D electron fluids. In this Letter we provide a theory of these frequency shifts, enabling a more quantitative interpretation of excitonic-sensing experiments, and apply it as an example to WSe$ _2$ that is proximate to graphene bilayers and multilayers.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Main: 5 pages, 4 figures; Supmat: 6 pages, 5 figures. Comments are welcome!
Hexagonal InOI monolayer: a 2D phase-change material combining topological insulator states and piezoelectricity
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-10-27 20:00 EDT
Wenhui Wan, Xinyue Liu, Yanfeng Ge, Ziqang Li, Yong Liu
Two-dimensional (2D) phase-change materials (PCMs) with moderate transition barriers and distinctly contrasting properties are highly desirable for multifunctional devices, yet such systems remain scarce. Using first-principles calculations, we propose a hexagonal InOI monolayer as a promising 2D PCM. This material exhibits two distinct polymorphs: an energetically favorable T$ ^{\prime}$ phase and a metastable T phase, differentiated by iodine atom positions. The T$ ^{\prime}$ -to-T structural phase transition features a moderate energy barrier $ E_b$ of 72.1 meV per formula unit, facilitating reversible switching. Notably, strain engineering tailors the electronic transition, inducing either a metal-to-topological-insulator or a metal-to-normal-insulator transformation. Additionally, this phase transition modulates the piezoelectric response and shifts optical absorption from the infrared to the visible range. These multifunctional properties make 2D hexagonal InOI highly promising for applications in non-volatile memory, low-contact-resistance spintronics, and optical switching devices.
Materials Science (cond-mat.mtrl-sci)
Swimming patterns of a multi-mode bacterial swimmer in fluid shear flow
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-10-27 20:00 EDT
Valeriia Muraveva, Agniva Datta, Jeungeun Park, Veronika Pfeifer, Yongsam Kim, Wanho Lee, Sookkyung Lim, Carsten Beta
Bacterial swimming is well characterized in uniform liquids at rest. The natural habitat of bacterial swimmers, however, is often dominated by moving fluids and interfaces, resulting in shear flows that may strongly alter bacterial navigation strategies. Here, we study how fluid shear flow affects the swimming motility of the soil bacterium Pseudomonas putida, a bacterial swimmer that moves in a versatile pattern composed of three different swimming modes, where the flagella may push, pull, or wrap around the cell body (multi-mode swimmer). We introduce a computer automated cell tracking and swimming mode detection tool to show that shear induced alignment depends on the swimming mode, while motility and proximity to surfaces counteract the alignment effect. Moreover, filament wrapping becomes less efficient with increasing shear stress. Numerical simulations of realistic swimmer geometries complement our experimental results, providing more detailed mechanistic insights into movement patterns of bacterial swimmers in a shear flow.
Soft Condensed Matter (cond-mat.soft), Biological Physics (physics.bio-ph)
11 pages, 7 figures
Kinetic theory of emulsions with matter supply
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-10-27 20:00 EDT
Jacqueline Janssen, Frank Jülicher, Christoph A. Weber
In this work, we propose a theory for the kinetics of emulsions in which a continuous supply of matter feeds droplet growth. We consider cases where growth is either limited by bulk diffusion or the transport through the droplets’ interfaces. Our theory extends the Lifshitz-Slyozov-Wagner (LSW) theory by two types of matter supply, where either the supersaturation is maintained or the supply rate is constant. In emulsions with maintained supersaturation, we find a decoupling of droplets at all times, with the droplet size distribution narrowing in the diffusion-limited regime and a drifting distribution of a fixed shape in the interface-resistance-limited case. In emulsions with a constant matter supply, there is a transition between narrowing and broadening in the diffusion-limited regime, and the distribution is non-universal. For the interface-resistance-limited regime, there is no transition to narrowing, and we find a universal law governing coarsening kinetics that is valid for any constant matter supply. The average radius evolves according to a power law that is independent of the matter supply, and we find a closed-form expression for the droplet size distribution function. Our theory is relevant to biological systems, such as biomolecular condensates in living cells, since droplet material is not conserved and the growth of small droplets is proposed to be interface-resistance-limited.
Soft Condensed Matter (cond-mat.soft), Biological Physics (physics.bio-ph)
ARPES of Bi2212 interpreted via a particle in a system of dynamic scatterers
New Submission | Superconductivity (cond-mat.supr-con) | 2025-10-27 20:00 EDT
In this work, I employ parabolic cylinder functions to quantitatively describe the ARPES spectra of an over-doped Bi2212 across the temperature range 6 - 140K at the antinode k-point. These functions come from the solutions of a particle moving in a system of random scatterers. The parameters, i.e. the overall amplitude (A), the spectral coherence scale (C), and the energy shift (EG), are determined directly by fitting to experimental data. At 140K, the dominated feature of the ARPES spectrum resembles the solution of a particle moving in a one-dimensional random system. According to the present model, the electronic states of the over-doped Bi2212 at the antinode k-point can be viewed as a realization of the theory of a particle moving in dynamic scatterers in 1D with corrections from the ground state solutions at lower temperature.
Superconductivity (cond-mat.supr-con)
23 pages, 12 figures
Critical Exponent of Dynamical Quantum Phase Transition in One-Dimensional Bose-Hubbard Model in the Strong Interacting Limit
New Submission | Quantum Gases (cond-mat.quant-gas) | 2025-10-27 20:00 EDT
We analytically investigated the dynamical quantum phase transitions in the Bose-Hubbard model using the Loschmidt echo as an observable, revealing that after a quench, the global Loschmidt echo exhibits cusp singularities with a logarithmically divergent rate function near criticality and a critical exponent of zero. Through extensive calculations across various system sizes and initial states, we have demonstrated that in the strongly interacting regime, the critical singularity of dynamical quantum phase transitions exhibits consistency across different model details and initial product states (charge-density wave states). Moreover, we find that modifying the harmonic potential well not only preserves the phase transition but also enables precise control over the transition timing.
Quantum Gases (cond-mat.quant-gas)
Direct observation of the crystal electric-field splitting under magnetic field and uncovering field-induced magnetic phase transition in triangular rare-earth magnet CsErSe$_2$
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-10-27 20:00 EDT
Hope Whitelock, Allen O. Scheie, Marissa McMaster, Ian A. Leahy, Li Xing, Mykhaylo Ozerov, Dmitry Smirnov, Eun Sang Choi, C. dela Cruz, M. O. Ajeesh, Eliana S. Krakovsky, Daniel Rehn, Jie Xing, Athena S. Sefat, Minhyea Lee
An indispensable step toward understanding magnetic interaction in rare-earth magnets is the determination of spatially anisotropic single-ion properties resulting from the crystal electric field (CEF) physics. The CEF Hamiltonian exhibits a discrete energy spectrum governed by a set of independent parameters that reflect the site symmetry of the magnetic ion. However, experimentally determining these parameters for magnetic ions at low-symmetry sites has been proven highly challenging. In this study, we directly measured the CEF level splitting under magnetic fields (B) using optical spectroscopy and extracted both CEF parameters and the exchange energies of a triangular insulating magnet CsErSe$ _2$ as a model system. With increasing field, we find many CEF levels undergo level-crossing, which accompanies switching of the eigenstate. Particularly, such a crossing occurring at the ground state results in a step-like increase in magnetization that we captured with the low-temperature AC magnetic susceptibility measurements. Our work demonstrates that the accurately determined CEF Hamiltonian parameters enable uncovering the rich physics of field-induced collective magnetic phenomena, and potentially lead to a new route to magnetic frustration.
Strongly Correlated Electrons (cond-mat.str-el)
13 pages, 9 figures
Zeeman Spectroscopy of Vacancy-Charge-Compensated Er3+ Sites in CaWO4 under Vector Magnetic Fields
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-10-27 20:00 EDT
Fabian Becker, Sudip KC, Lorenz J. J. Sauerzopf, Tim Schneider, Luis Risinger, Christian Schmid, Kai Müller
We present polarization-resolved optical absorption measurements on Er3+ ions in CaWO4 under vector magnetic fields, focusing on charge-compensated sites arising from local Ca2+ vacancies. While the known axial Er3+ site displays a single symmetric Zeeman-split transition pattern consistent with S4 symmetry, two additional sites exhibit more complex spectral behavior, including sets of transitions that interchange under 90° crystal rotations-evidence of reduced, rhombic-like symmetry. From these polarization- and temperature-dependent spectra, we extract effective g-factors. Our findings are corroborated by electron paramagnetic resonance measurements and support a model of multiple inequivalent Ca2+ vacancies around Er3+ sites in the host lattice. This detailed characterization contributes to understanding defect-engineered rare-earth sites for quantum information applications.
Materials Science (cond-mat.mtrl-sci)
Tailoring dispersion and evanescent modes in multimodal nonlocal lattices using positive-only interactions
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-10-27 20:00 EDT
Metamaterials derive their unconventional properties from engineered microstructures, with periodic lattices providing a versatile framework for modeling wave propagation. Dispersion relations, obtained from Bloch-Floquet theory, govern how waves propagate, attenuate, or localize within such systems. Extending interactions beyond nearest neighbors, through nonlocality, substantially enriches the design space of band diagrams, enabling phenomena such as negative or zero group velocities, roton-like extrema, and band-gap localization. However, existing approaches to dispersion tailoring often rely on analytical formulations or Fourier-based identifications, which become impractical for complex coupling mechanisms and offer limited control over physical constraints such as stiffness positivity. This work introduces a general interpolation-based framework for customizing dispersion relations in uniform nonlocal lattices. Rather than reconstructing full dispersion curves, the method enforces prescribed frequency-wavenumber points as interpolation constraints, enabling localized and tunable control of wave behavior. The formulation is applied to both spring- and beam-interaction lattices, and demonstrated on an Euler-Bernoulli beam model with adjustable nonlocal couplings. Through systematic parameter tuning, the framework enables the creation of rotons, the adjustment of group-velocity dispersion, and the design of evanescent waves with controlled exponential decay within band gaps, all while ensuring real, positive-only stiffness parameters and passive mechanical behavior. Altogether, this parametric interpolation strategy provides a physically consistent and computationally efficient route for engineering advanced phononic functionalities in periodic nonlocal systems.
Materials Science (cond-mat.mtrl-sci)
Preprint also available on HAL: this https URL
Identification of 2D colloidal assemblies in images: a threshold processing method versus machine learning
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-10-27 20:00 EDT
L. T. Khusainova, K.S. Kolegov
This paper is devoted to the problem of identification of colloidal assemblies using the example of two-dimensional coatings (monolayer assemblies). Colloidal systems are used in various fields of science and technology, for example, in applications for photonics and functional coatings. The physical properties depend on the morphology of the structure of the colloidal assemblies. Therefore, effective identification of particle assemblies is of interest. The following classification is considered here: isolated particles, dimers, chains and clusters. We have studied and compared two identification methods: image threshold analysis using the OpenCV library and machine learning using the YOLOv8 model as an example. The features and current results of training a neural network model on a dataset specially prepared for this work are described. A comparative characteristic of both methods is given. The best result was shown by the machine learning method (97% accuracy). The threshold processing method showed an accuracy of about 68%. The developed algorithms and software modules may be useful to scientists and engineers working in the field of materials science in the future.
Soft Condensed Matter (cond-mat.soft)
Beyond Poisson: First-Passage Asymptotics of Renewal Shot Noise
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-10-27 20:00 EDT
The first-passage time (FPT) of a stochastic signal to a threshold is a fundamental observable across physics, biology, and finance. While renewal shot noise is a canonical model for such signals, analytical results for its FPT have remained confined to the Poisson (Markovian) case, despite the prevalence of non-Poisson arrival statistics in applications from neuronal spiking to gene expression. We break this long-standing barrier by deriving the first universal asymptotic formula for the mean FPT $ \langle T_b \rangle$ to reach level $ b$ for renewal shot noise with general arrival statistics and exponential marks. Our central result is a closed-form expression that reveals precisely how general inter-arrival statistics impact the naive Arrhenius law. We show that the short-time behavior of the interarrival distribution dictates universal scaling corrections, ranging from stretched-exponential to algebraic, that can dramatically accelerate threshold crossing. Furthermore, we argue and confirm numerically that the full FPT distribution becomes exponential at large thresholds, implying that $ \langle T_b \rangle$ provides a complete asymptotic characterization. Our work, enabled by a novel exact solution for the moments of the noise, establishes a general framework for analyzing extreme events in non-Markovian systems with relaxation.
Statistical Mechanics (cond-mat.stat-mech), Probability (math.PR)
The Piezochiral Effect
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-10-27 20:00 EDT
Z. Zeng, M. Först, M. Fechner, X. Deng, A. Cavalleri, P.G. Radaelli
Chirality is a pervasive property of matter that underpins many important phenomena across physics, chemistry and biology. Given its broad significance, the development of protocols for rational control of chirality in solid state systems is highly desirable, especially if this effect can be tuned continuously and in two directions. Yet, this goal has remained elusive due to the absence of a universal conjugate field that couples linearly to this structural order. Here, we introduce the piezochiral effect, which enables control of chirality through mechanical strain. We first show by symmetry analysis that uniaxial strain induces chirality in a broad class of achiral crystals that host fragments of opposite chirality within each unit cell, an effect that has so far remained unrecognized. The strain-induced handedness can be tuned either by changing the strain direction or by switching between compressive and tensile strain. We experimentally verify this effect in AgGaS2, using measurements of the optical activity under strain. Our discovery establishes a new scheme for chirality control, with potential applications that range from spintronics to asymmetric catalysis, and enantioselective interactions in biosystems.
Materials Science (cond-mat.mtrl-sci)
6 pages, 4 figures + Supplementary Information
Markov Inequality as a Tool for Linear-Scaling Estimation of Local Observables
New Submission | Disordered Systems and Neural Networks (cond-mat.dis-nn) | 2025-10-27 20:00 EDT
H. P. Veiga, D. R. Pinheiro, J. P. Santos Pires, J. M. Viana Parente Lopes
We introduce a linear-scaling stochastic method to compute real-space maps of any positive local spectral operator in a tight-binding model. By employing positive-definite estimators, the sampling error at each site can be rigorously bounded relative to the mean via the Markov inequality, overcoming the lack of self-averaging and enabling accurate estimates even under strong spatial fluctuations. The approach extends to non-diagonal observables, such as local currents, through local unitary transformations and its effectiveness is showcased by benchmark calculations in the disordered two-dimensional (2D) $ \pi$ -flux model, where the LDoS and steady-state current maps are computed. This method will enable simulations of disorder-driven mesoscopic phenomena in realistically large lattices and accelerate real-space self-consistent mean-field calculations.
Disordered Systems and Neural Networks (cond-mat.dis-nn), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
5 pages, 4 figures