CMP Journal 2025-08-22
Statistics
Nature Materials: 1
Nature Physics: 2
Physical Review Letters: 14
Physical Review X: 1
arXiv: 70
Nature Materials
Uniform conjugated polymer rectangular platelets exhibiting long-range exciton diffusion
Original Paper | Self-assembly | 2025-08-21 20:00 EDT
Jiandong Cai, Xian Wei Chua, Chen Li, Jeannine Grüne, Pratyush Ghosh, Yuanfei Ding, Harvey K. MacKenzie, Huibin Qiu, Neil C. Greenham, Akshay Rao, Ian Manners
The creation of discrete organic semiconducting two-dimensional nanomaterials with high crystalline order, controlled dimensions and enhanced energy transport capability represents a major challenge. We describe the preparation of uniform rectangular platelet micelles comprising a highly ordered, crystalline semiconducting poly(di-n-hexylfluorene) core by means of seeded growth methods. The rectangular core is constructed by the π-π stacking of tilted fluorene units and the solvophobic stacking of alkyl side chains. The core structure enables long-range anisotropic exciton diffusion, particularly in the direction of interchain π-π stacking, with a diffusion coefficient of up to 2.56 ± 0.52 cm2 s-1 and diffusion lengths of >500 nm. The segmented platelet comicelles, with concentric patches comprising distinct coronas, exhibit efficient energy transfer over hundreds of nanometres from the central higher-energy core to the peripheral lower-energy polythiophene corona. Our results open emerging avenues for the design of two-dimensional organic-semiconductor-based nanostructures, which could find applications in optoelectronics, sensing and photocatalysis.
Self-assembly, Two-dimensional materials
Nature Physics
Magnon-polarons in the Fermi-Hubbard model
Original Paper | Quantum simulation | 2025-08-21 20:00 EDT
Max L. Prichard, Zengli Ba, Ivan Morera, Benjamin M. Spar, David A. Huse, Eugene Demler, Waseem S. Bakr
The interplay of magnetic excitations and itinerant charge carriers is a ubiquitous phenomenon in strongly correlated electron systems. A key theoretical question is understanding the renormalization of the magnon quasiparticle, a collective spin excitation, upon doping a magnetic insulator. Here we observe a new type of quasiparticle–a magnon-Fermi-polaron–arising from the dressing of a magnon with the doped holes of a cold-atom Fermi-Hubbard system. Using Raman excitation with controlled momentum in a doped, spin-polarized band insulator, we address the spectroscopic properties of the magnon-polaron. In an undoped system with strong interactions, photoexcitation produces magnons, whose properties are accurately described by spin-wave theory. We measure the evolution of the photoexcitation spectra as we move away from this limit to produce magnon-polarons due to dressing of the magnons by charge excitations. We observe a shift in the polaron energy with doping that is strongly dependent on the injected momentum, accompanied by a reduction of spectral weight in the probed energy window. We anticipate that the technique introduced here, which is the analogue of inelastic neutron scattering, will provide atomic quantum simulators with access to the dynamics of a wide variety of excitations in strongly correlated phases.
Quantum simulation, Ultracold gases
Bloch oscillations of a soliton in a one-dimensional quantum fluid
Original Paper | Quantum mechanics | 2025-08-21 20:00 EDT
F. Rabec, G. Chauveau, G. Brochier, S. Nascimbene, J. Dalibard, J. Beugnon
The motion of a quantum system under an external force often challenges classical intuition. A notable example is the dynamics of a single particle in a periodic potential, which undergoes Bloch oscillations under the action of a constant force. Similar oscillations can also occur in one-dimensional quantum fluids without a lattice. The generalization of Bloch oscillations to a weakly bounded ensemble of interacting particles has so far been limited to the experimental study of the two-particle case, where the observed period is halved compared to the single-particle case. In this work, we observe the oscillations of the position of a mesoscopic solitonic wave packet–consisting of approximately 1,000 atoms–in a one-dimensional Bose gas subjected to a constant uniform force and in the absence of a lattice potential. The oscillation period scales inversely with the number of atoms, revealing its collective nature. We demonstrate the role of the phase coherence of the quantum bath in which the wave packet moves and investigate the underlying topology of the associated superfluid currents. Our measurements highlight the periodicity of the dispersion relation of collective excitations in one-dimensional quantum systems.
Quantum mechanics, Ultracold gases
Physical Review Letters
Exponential Quantum Speedup for Simulating Classical Lattice Dynamics
Research article | Lattice dynamics | 2025-08-21 06:00 EDT
Xiantao Li
Simulating large-scale lattice dynamics remains a long-standing challenge in condensed matter and materials science, where mechanical and thermal behaviors arise from coupled vibrational modes. We introduce a quantum algorithm that reformulates general harmonic lattice dynamics as a time-dependent Schr"odinger equation governed by a sparse, Hermitian Hamiltonian. This enables the use of Hamiltonian simulation techniques on quantum devices, offering exponential speedup in the number of atoms $N$. Our approach applies to arbitrary harmonic lattices with vector-valued dynamics. A key ingredient is a matrix-valued Fej'er-Riesz factorization of the phonon dynamical matrix, which preserves translational symmetry and enables efficient assembly of the Hamiltonian operator. We demonstrate the method’s applicability across a broad class of lattice models.
Phys. Rev. Lett. 135, 080602 (2025)
Lattice dynamics, Quantum computation, Quantum simulation
Photon-Interfaced Ten-Qubit Register of Trapped Ions
Research article | Atoms, ions, & molecules in cavities | 2025-08-21 06:00 EDT
M. Canteri, Z. X. Koong, J. Bate, A. Winkler, V. Krutyanskiy, and B. P. Lanyon
Establishing networks of quantum processors offers a path to scalable quantum computing and applications in communication and sensing. This requires first developing efficient interfaces between photons and multiqubit registers. In this Letter, we show how to entangle each individual matter qubit in a register of ten to a separate traveling photon. The qubits are encoded in a string of cotrapped atomic ions. By switching the trap confinement, ions are brought one at a time into the waist of an optical cavity and emit a photon via a laser-driven cavity-mediated Raman transition. The result is a train of photonic qubits, each near-maximally entangled by their polarization with a different ion qubit in the string. An average ion-photon Bell state fidelity of 92% is achieved, for an average probability for detecting each single photon of 9%. The technique is directly scalable to larger ion-qubit registers and opens up the near-term possibility of entangling distributed networks of trapped-ion quantum processors, sensing arrays, and clocks.
Phys. Rev. Lett. 135, 080801 (2025)
Atoms, ions, & molecules in cavities, Light-matter interaction, Quantum information with trapped ions, Quantum networks, Quantum optics, Single photon sources
Positive Neutrino Masses with DESI DR2 via Matter Conversion to Dark Energy
Research article | Cosmological parameters | 2025-08-21 06:00 EDT
S. P. Ahlen et al. (DESI Collaboration)
*et al.*An alternative to the standard cosmological model where matter is converted to dark energy during stellar collapse results in an accurate cosmological expansion history and a summed neutrino mass posterior distribution peaked at positive mass.
Phys. Rev. Lett. 135, 081003 (2025)
Cosmological parameters, Dark energy, Astronomical black holes, Neutrinos
Resurgence of $T\overline{T}$-Deformed Partition Function
Research article | Conformal field theory | 2025-08-21 06:00 EDT
Jie Gu, Yunfeng Jiang, and Huajia Wang
We study nonperturbative effects of torus partition function of the $T\overline{T}$-deformed 2D conformal field theory (CFT) by resurgence in this Letter and a companion paper. The deformed partition function can be written as an infinite series of the deformation parameter $\lambda $. We develop highly efficient methods to compute perturbative coefficients in the $\lambda $ expansion. To exemplify, the first 600 coefficients for the $T\overline{T}$-deformed free boson and free fermion are computed. The method can be generalized to any rational CFTs; we present the key idea in this Letter while relegating details and results to the companion paper. Equipped with the large order perturbative data, we provide convincing numerical evidence that the $\lambda $ series is asymptotic and not Borel resummable. We extract the nonperturbative contribution by resurgence and propose that they originate from new complex saddle points after analytically continuing the modular parameters in the integral representation of the partition function. The proposal is checked by comparing the predicted asymptotic behavior of the coefficients and large order perturbative data, which match nicely. The implications of these nonperturbative contributions for the Stokes phenomenon, which relates the positive and negative signs of $\lambda $, as well as possible comparisons with holography, is also discussed.
Phys. Rev. Lett. 135, 081601 (2025)
Conformal field theory, Integrability in field theory
Search for an Anomalous Production of Charged-Current ${\nu }_{e}$ Interactions without Visible Pions across Multiple Kinematic Observables in MicroBooNE
Research article | Hypothetical particle physics models | 2025-08-21 06:00 EDT
P. Abratenko et al. (MicroBooNE Collaboration)
*et al.*The MicroBooNE experiment’s five-year dataset has shown that an unpredicted neutrino-flavor oscillation is not the cause of anomalous results obtained by its predecessor.
Phys. Rev. Lett. 135, 081802 (2025)
Hypothetical particle physics models, Neutrinos, Pions
Space-Time Optical Hopfion Crystals
Research article | Polarization of light | 2025-08-21 06:00 EDT
Wenbo Lin, Nilo Mata-Cervera, Yasutomo Ota, Yijie Shen, and Satoshi Iwamoto
Hopfions—higher-dimensional topological quasiparticles with sophisticated 3D knotted spin textures discovered in condensed matter and photonic systems—show promise in high-density data storage and transfer. Here, we present crystalline structures of hopfions lying in space-time constructed by spatiotemporally structured light. Practical methodologies using bichromatic structured light beams or dipole arrays to assemble 1D and higher dimensional hopfion lattices are proposed, and a technique for tailoring topological orders is elucidated. Optical hopfion crystals constitute a new platform for high-dimensional topological information transfer.
Phys. Rev. Lett. 135, 083801 (2025)
Polarization of light, Spatial profiles of optical beams, Structured light, Topological effects in photonic systems
Meniscus-Driven Modulation of Surface Wave Transmission across a Barrier
Research article | Capillary waves | 2025-08-21 06:00 EDT
Zhengwu Wang, Guoqin Liu, and Likun Zhang
Meniscus oscillations at interfaces between liquids, solids, and air significantly impact fluid dynamics and control. While idealized models exist, experimental data on capillary–gravity wave scattering involving meniscus effects remain limited. In this Letter, we systematically measured wave transmission past a surface-piercing barrier, focusing on meniscus effects. By varying the barrier’s surface properties and the wave frequencies, we explored how meniscus deformation influences wave transmission. The results are compared with simulations and limiting-case theories. We interpret that the meniscus water column formed beneath the barrier enhances flow coupling and increases wave transmission, while meniscus surface bending suppresses it by constraining motion. These competing effects explain the observed frequency and contact angle dependencies. Our findings provide insights into how meniscus dynamics govern surface wave behavior.
Phys. Rev. Lett. 135, 084001 (2025)
Capillary waves, Contact line dynamics, Surface gravity waves, Surface tension effects, Wave scattering, Wave-structure interactions
Demonstration of a Novel Radiochemical Mix Diagnostic for Fusion Implosions at the National Ignition Facility
Research article | Charge-exchange reactions | 2025-08-21 06:00 EDT
S. A. MacLaren, E. L. Dewald, D. A. Martinez, N. Gharibyan, K. Moody, C. Horwood, P. J. Bedrossian, R. D. Hoffman, G. B. Zimmerman, H. W. Xu, C. Kong, K. Sequoia, J. E. Pino, R. E. Tipton, D. D.-M. Ho, C. V. Young, J. D. Despotopulos, K. N. Kmak, D. A. Shaughnessy, S. Prisbrey, H. Huang, M. Ratledge, and N. Rice
Mixing of the ablator material into the fuel of an inertial confinement fusion implosion reduces compression and enhances radiative losses, preventing ignition. We describe a novel use of charged-particle radiochemistry to measure the ablator mix in contact with the fusion hot spot. The capsule uses a graded Be-Cr layer to increase the confinement of the hot spot. $^{52}\mathrm{Mn}$ and $^{51}\mathrm{Cr}$ isotopes are collected from the implosion and counted, and the ratio is related to the amount of Cr mixed into the hot spot. Thus, a new diagnostic to determine the degradation due to mix on fusion implosions has been developed.
Phys. Rev. Lett. 135, 085101 (2025)
Charge-exchange reactions, High-energy-density plasmas, Indirect drive
Microscopic Mechanism of Coexisting Electron Spin Resonance and Kondo Resonance in a Single Iron Phthalocyanine Molecule
Research article | Electronic structure of atoms & molecules | 2025-08-21 06:00 EDT
Qi Chen, Hongjian Du, Xinyong Meng, Jufeng Wang, Jingzun Liao, Bin Li, Wei Hu, Qitang Fan, Shijing Tan, Chuanxu Ma, Jinlong Yang, J. G. Hou, and Bing Wang
The multiplicity of orbitals in quantum systems significantly influences the competition between Kondo screening and local spin magnetization. The identification of orbital-specific processes is essential for advancing spintronic devices, as well as for enhancing the understanding of many-body quantum phenomena, but it remains a great challenge. Here, we use a combination of scanning tunneling microscopy/spectroscopy and electron spin resonance (ESR) spectroscopy to investigate single iron phthalocyanine (FePc) molecules on $\mathrm{MgO}/\mathrm{Ag}(100)$. We observe the coexistence of ESR and Kondo resonance from the Fe(II) ion center at a temperature well below the Kondo temperature ${T}{\mathrm{K}}$, where the magnetic moments are determined to be 1 Bohr magneton ($1{\mu }{\mathrm{B}}$), corresponding to a spin $S=1/2$ state in either of the ESR and Kondo resonance channels. On the basis of the observed in-plane twofold symmetry in the spatial distribution of ESR linewidths, in combination with density functional theory calculations, we attribute one spin $S=1/2$ state in the degeneracy-lifted ${d}{\pi }$ orbital to the ESR channel, and the other in the highly screenable ${d}{ {z}^{2}}$ orbital to the Kondo resonance, respectively, within the framework of the $S=1$ two-channel Kondo model of an ordinary Fermi liquid.
Phys. Rev. Lett. 135, 086403 (2025)
Electronic structure of atoms & molecules, Kondo effect, Density functional theory, Electron spin resonance, Scanning tunneling microscopy, Scanning tunneling spectroscopy
Attosecond All-Optical Retrieval of Valley Polarization via Circular Dichroism in Transient Absorption
Research article | Ultrafast optics | 2025-08-21 06:00 EDT
Wenqing Li, Xiaosong Zhu, Pengfei Lan, Liang Li, Kai Wang, Wanzhu He, Hannes Hübener, Umberto De Giovannini, and Peixiang Lu
We propose a scheme for retrieving the ultrafast valley polarization (VP) dynamics in two-dimensional hexagonal materials via attosecond circular dichroism (CD) transient absorption spectroscopy. This approach builds on the CD transition between the first and higher conduction bands induced by the circularly polarized probe pulses. The population imbalance at nonequivalent valleys in the first conduction band is proportionally mapped onto the difference in absorption coefficients of two probe pulses with opposite helicities, supporting an unprecedented quantitative retrieval of the corresponding VP dynamics with subfemtosecond time resolution. We theoretically demonstrate the scheme for $h$-BN and ${\mathrm{MoS}}_{2}$ through ab initio calculations, achieving an accurate retrieval of the VP dynamics, particularly the transient VP switching processes, with a time resolution of 250 as.
Phys. Rev. Lett. 135, 086404 (2025)
Ultrafast optics, Ultrafast phenomena, Valley degrees of freedom, 2-dimensional systems, Time-dependent DFT
Strong Magnon-Phonon Coupling in the Kagome Antiferromagnets
Research article | Frustrated magnetism | 2025-08-21 06:00 EDT
A. S. Sukhanov, O. I. Utesov, A. N. Korshunov, N. D. Andriushin, M. S. Pavlovskii, S. E. Nikitin, A. A. Kulbakov, K. Manna, C. Felser, and M. C. Rahn
Inelastic x-ray scattering, first-principles simulations, and analytical derivations combine to show how the exchange coupling between the kagome layers in a frustrated antiferromagnet drives unique zone-centered magnon polarons.
Phys. Rev. Lett. 135, 086703 (2025)
Frustrated magnetism, Magnetoelastic effect, Polarons, Kagome metal, Noncollinear magnets, Density functional theory, Inelastic X-ray scattering, Spin wave theory
Self-Reinforcing Cascades: A Spreading Model for Beliefs or Products of Varying Intensity or Quality
Research article | Cascades | 2025-08-21 06:00 EDT
Laurent Hébert-Dufresne, Juniper Lovato, Giulio Burgio, James P. Gleeson, S. Redner, and P. L. Krapivsky
Models of how things spread often assume that transmission mechanisms are fixed over time. However, social contagions—the spread of ideas, beliefs, innovations—can lose or gain in momentum as they spread: ideas can get reinforced, beliefs strengthened, products refined. We study the impacts of such self-reinforcement mechanisms in cascade dynamics. We use different mathematical modeling techniques to capture the recursive, yet changing nature of the process. We find a critical regime with a range of power-law cascade size distributions with nonuniversal scaling exponents. This regime clashes with classic models, where criticality requires fine-tuning at a precise critical point. Self-reinforced cascades produce critical-like behavior over a wide range of parameters, which may help explain the ubiquity of power-law distributions in empirical social data.
Phys. Rev. Lett. 135, 087401 (2025)
Cascades, Complex systems, Random walks, Spreading, Rumor spreading, Spreading models
Inescapable Anisotropy of Nonreciprocal XY Models
Research article | Flocking | 2025-08-21 06:00 EDT
Dawid Dopierala, Hugues Chaté, Xia-qing Shi, and Alexandre Solon
We investigate nonreciprocal XY (NRXY) models defined on two-dimensional lattices in which the coupling strength of a spin with its neighbors varies with their position in the frame defined by the current spin orientation. As expected from the seminal work of Dadhichi et al., [Nonmutual torques and the unimportance of motility for long-range order in two-dimensional flocks, Phys. Rev. E 101, 052601 (2020)], we first show that nonreciprocity is akin to a self-propulsion: we derive a mean-field continuous theory identical to that of constant-density flocks. Like the latter, NRXY models exhibit a long-range ordered phase that is metastable to the nucleation of topological defects, and their asymptotic state is a dynamic foam of asters. We then show that in the metastable ordered phase, the lattice always induces anisotropy on large scales, pinning the direction of order and imposing a finite correlation length. Crucially, we demonstrate that this anisotropy is inescapable since, even when not explicitly present in the interaction rule, it is generated by fluctuations. In short, the ordered phase of lattice NRXY models is that of active clock models.
Phys. Rev. Lett. 135, 088302 (2025)
Flocking, Dry active matter, Living matter & active matter
Ordering and Defect Cloaking in Nonreciprocal Lattice XY Models
Research article | Dry active matter | 2025-08-21 06:00 EDT
Pankaj Popli, Ananyo Maitra, and Sriram Ramaswamy
We present a detailed analytical and numerical examination, on square and triangular lattices, of the nonreciprocal planar spin model introduced in Dadhichi et al. [Phys. Rev. E 101, 052601 (2020)]. We show that the effect of lattice anisotropy should persist at large scales, leading to a ‘’mass’’ for the angle field of the spins, and behavior not in the ‘’Malthusian Toner-Tu’’ [Phys. Rev. Lett. 108, 088102 (2012)] universality class. Numerically, we find evidence of this mass at large values of our nonreciprocity parameter; for smaller values, we find power-law scaling of long-wavelength equal-time correlators in the polar-ordered phase of our lattice model over the system sizes and wave number range explored. Focussing on topological defects, we show numerically that defect interactions are highly anisotropic with respect to the mean ordering direction. In particular, the constituents of a $\pm{}1$ pair are shielded from each other in a class of configurations, deferring their annihilation and allowing time for the nucleation of further defects. The result, we show numerically, is the destruction of the polarized phase via an aster apocalypse reminiscent of that found by Besse et al. [Phys. Rev. Lett. 129, 268003 (2022)] for flocks without number conservation.
Phys. Rev. Lett. 135, 088303 (2025)
Dry active matter, Flocks, Living matter & active matter, Theories of collective dynamics & active matter
Physical Review X
Energy Shifts and Broadening of Excitonic Resonances in Electrostatically Doped Semiconductors
Research article | Excitons | 2025-08-21 06:00 EDT
Hanan Dery, Cedric Robert, Scott A. Crooker, Xavier Marie, and Dinh Van Tuan
Two fundamental concepts–distinguishability and optimality–are primary factors that govern the behavior of optical resonances in charge-tunable semiconductors.
Phys. Rev. X 15, 031049 (2025)
Excitons, Trions, Valley degrees of freedom, Semiconductors, Luminescence, Photoluminescence, Reflectivity
arXiv
Thermodynamics of dilute anyon gases from fusion constraints
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-08-22 20:00 EDT
Yuto Nakajima, Umang Mehta, Hart Goldman
Recent measurements on 2d materials tuning between fractional quantum anomalous Hall phases and a plethora of correlated electronic states call for a detailed understanding of the dynamics of anyons. Here we develop a general theory of the statistical mechanics of anyon gases at finite temperature, valid in regimes where the anyons are sufficiently dilute and can be treated as weakly interacting particles. We find that with a minimal set of universal braiding and fusion data, along with information about the hierarchy of anyon gaps, it is possible to construct a distribution function for any dilute anyon gas, as well as derive thermodynamic observables. Our results are built on an anyon exclusion principle manifesting as a constraint on fusion outcomes of physical states. Our approach unifies and streamlines a range of results for itinerant anyon models, from solvable lattice Hamiltonians to large-N field theories.
Strongly Correlated Electrons (cond-mat.str-el), Mesoscale and Nanoscale Physics (cond-mat.mes-hall), High Energy Physics - Theory (hep-th)
63 pages, 6 figures
Superdielectrics: Disorder-induced perfect screening in insulators
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-08-22 20:00 EDT
Ilia Komissarov, Tobias Holder, Raquel Queiroz
We study the relationship between the quantities that encode the insulating properties of matter: the ground-state quantum metric, the average localization length, and the electric susceptibility. By examining the one-dimensional Anderson insulator model and the Su-Schrieffer-Heeger chain with chiral disorder, we demonstrate that the former two measures are proportional in one-dimensional systems near criticality, and both are determined by the properties of the hybridized localized states around the Fermi energy. We employ these insights to demonstrate that the behavior of the electric susceptibility is drastically different in the bond-disordered SSH chain, with the possibility that it may diverge even when the localization length and the quantum metric remain finite. This divergence, caused by the proliferation of impurity resonances at a particular energy, leads to a novel regime that exhibits mixed characteristics of metals and insulators. We term this regime superdielectric: an insulating state characterized by a finite quantum metric and divergent static electric susceptibility, which implies perfect screening in the absence of the dc conductivity. We demonstrate that the superdielectric phase also emerges in higher-dimensional materials, such as graphene with vacancies and Kekulé bond distortion.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Disordered Systems and Neural Networks (cond-mat.dis-nn)
15 pages, 8 figures
The beginning of the endpoint bootstrap for conformal line defects
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-08-22 20:00 EDT
Ryan A. Lanzetta, Shang Liu, Max A. Metlitski
A challenge in the study of conformal field theory (CFT) is to characterize the possible defects in specific bulk CFTs. Given the success of numerical bootstrap techniques applied to the characterization of bulk CFTs, it is desirable to develop similar tools to study conformal defects. In this work, we successfully demonstrate this possibility for endable conformal line defects. We achieve this by incorporating the endpoints of a conformal line defect into the numerical four-point bootstrap and exploit novel crossing symmetry relations that mix bulk and defect CFT data in a way that further possesses positivity, so that rigorous numerical bootstrap techniques are applicable. We implement this approach for the pinning field line defect of the $ 3d$ Ising CFT, obtaining estimates of its defect CFT data that agree well with other recent estimates, particularly those obtained via the fuzzy sphere regularization. An interesting consequence of our bounds is nearly rigorous evidence that the $ \mathbb Z_2$ -symmetric defect exhibiting long range order obtained as a direct sum of two conjugate pinning field defects is unstable to domain wall proliferation.
Strongly Correlated Electrons (cond-mat.str-el), Statistical Mechanics (cond-mat.stat-mech), High Energy Physics - Theory (hep-th)
83 pages, 17 figures
Beyond Superexchange: Emergent Unconventional Ferromagnetism in Thin-Film Sandwich Structures of Intrinsic Magnetic Topological Insulators
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-08-22 20:00 EDT
Takuya Takashiro, Ryota Akiyama, Ryotaro Minakawa, Shuji Hasegawa
In this work, we investigate the nature of magnetic interactions in intrinsic magnetic topological insulator Mn(Bi1-xSbx)2Te4 (MBST in short) systems, which possesses highly-ordered ferromagnetic septuple-layers (SLs), using two types of structures: MBST(1 SL)/(Bi1-xSbx)2Te3 heterostructures and MBST(1 SL)/(Bi1-xSbx)2Te3/MBST(1 SL) sandwich structures. The out-of-plane magnetization in the sandwich structure turned out to be significantly larger than that in the heterostructure, indicating that the interlayer magnetic interaction between two MBST layers is ferromagnetic. Furthermore, the Curie temperature increased with decreasing the in-plane Mn-Mn distance in the MBST layer, which suggests the enhancement of the intralayer ferromagnetic interaction within each MBST layer. Meanwhile, in the sandwich structures with various spacer thicknesses, the Curie temperature with the spacer layer was higher than that with no spacer layer. In addition, the curve shape of anomalous Hall effects for the sandwich structure was almost unchanged by carrier-density modulation, which implies that the ferromagnetism in this system is carrier-independent. Based on the above results, magnetic behaviors in our systems cannot be explained only by the direct exchange nor superexchange interactions reported previously for MBST systems, and are instead proposed to arise from topology-related mechanisms such as the van Vleck and Bloembergen-Rowland mechanisms. This work provides a new perspective on magnetic mechanisms in MBST systems, which helps us to realize next-generation spintronic and electronic devices by flexibly controlling magnetism in intrinsic magnetic topological insulators.
Materials Science (cond-mat.mtrl-sci), Other Condensed Matter (cond-mat.other)
45 pages and 10 figures
Probing Magnetic Properties of RuO$_{2}$ Heterostructures Through the Ferromagnetic Layer
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-08-22 20:00 EDT
Frank M. Abel, Subhash Bhatt, Shelby S. Fields, Vinay Sharma, Dai Q. Ho, Daniel Wines, D. Quang To, Joseph C. Prestigiacomo, Tehseen Adel, Riccardo Torsi, Maria F. Munoz, David T. Plouff, Xinhao Wang, Brian Donovan, Don Heiman, Gregory M. Stephen, Adam L. Friedman, Garnett W. Bryant, Anderson Janotti, Michelle E. Jamer, Angela R. Hight Walker, John Q. Xiao, Steven P. Bennett
RuO$ _{2}$ has been proposed as the prototypical altermagnetic material. However, several reports have recently questioned its intrinsic magnetic ordering, leading to conflicting findings, especially in thin film heterostructures pointing to possible interface effects being convoluted with supposed antiferromagnetic/altermagnetic signatures. Here, extensive magnetometry measurements were performed on two independently grown thin film heterostructures of RuO$ _{2}$ interfaced with either NiFe or Fe acting as the ferromagnetic layer. Below about 15 K, both samples exhibit exchange bias fields when cooled to approximately 2 K in a $ +$ 1 T field, and a spin transitional feature is observed around 31 K. Magneto-Raman measurements on RuO$ _{2}$ thin films only reveal a magnon mode when there is a NiFe layer, suggesting that RuO$ _{2}$ does not intrinsically possess long range magnetic ordering.. When in contact with a ferromagnet, RuO$ _2$ displays effects that could be ascribed to antiferromagnetism. However, the lack of intrinsic magnon modes points toward possible diffusion between the layers or spin disorder at the interface as seen by density functional theory (DFT) calculations.
Materials Science (cond-mat.mtrl-sci)
Intermediate-temperature specific heat of solids and the rationale behind the Maier-Kelley empirical formula
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-08-22 20:00 EDT
Valmir Ribeiro, Fernando Parisio
The heat capacity of solids at intermediate-to-high temperatures is of fundamental importance to several fields ranging from geology to material science. It depends on a variety of factors, with anharmonicity and, ultimately, melting playing a pivotal role. In this work we develop a first-principles model from an analytically tractable semi-harmonic oscillator Hamiltonian. The resulting specific heat expression depends not only on the Einstein temperature of the material but also on other physical parameters. We compare our predictions with experimental data for copper, aluminum, lead, silicon, and germanium with rather satisfactory results, especially considering that there are no fitting parameters in our theory. We finish this work by showing that our results formally justify the otherwise purely empirical formula by Maier and Kelley, also providing its coefficients in terms of elementary physical quantities.
Materials Science (cond-mat.mtrl-sci), Other Condensed Matter (cond-mat.other), Statistical Mechanics (cond-mat.stat-mech)
Disordered origins, deterministic outcomes: How the architecture of elastic networks imprints relaxed structure and mechanics
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-08-22 20:00 EDT
Stefanie Heyden, Mohit Pundir, Eric R. Dufresne, David S. Kammer
This work targets the influence of disorder on the relaxed structure and macroscopic mechanical properties of elastic networks. We construct network classes of different types of disorder (length, topology and stiffness), which are subsequently equilibrated in a finite kinematics setting. Relaxed network structures are distinct among network classes, which opens the path towards exploiting easily accessible experimental measures as a way of inferring further microstructural details.
Soft Condensed Matter (cond-mat.soft)
Polarization Mechanism of Bacteria Motion in Aquatic Media
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-08-22 20:00 EDT
Bohdan Lev (1, 2 and 3), Oleksandr Cherniak (1) ((1) Bogolyubov Institute for Theoretical Physics of NAS of Ukraine (2) Jozef Stefan Institute and (3) University of Ljubljana)
A new model of light-induced bacteria motion in an aqueous medium is proposed. The model concerns bacteria both with and without flagellae. It is based on the hydrodynamics of active matter and allows for the changes of polarization of both bacteria and the medium. Natural light is assumed to intensify the motion of clusters with different refraction indices within the bacteria and to modify their polarization. Such motion of polarized globules causes an increase in deformations and inhomogeneous polarization distribution on the bacteria surfaces. The free energy functional is used to calculate the perturbation of the bacteria surfaces and inhomogeneous polarization distributions that may either move along the bacteria or rotate. Mechanical interaction of surface deformations with water flows or interaction of the inhomogeneous polarization with free charges causes bacteria motion in the medium. Estimates of the bacteria motion velocity in the case of the proposed mechanism are made and it corresponded to experimentally observed values.
Soft Condensed Matter (cond-mat.soft)
11 pages, 2 figures with 7 panels
Entropy-Seebeck ratio as a tool for elementary charge determination
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-08-22 20:00 EDT
Francisco J. Peña, Cesar Nuñez, Bastian Castorene, Michel Aguilera, Natalia Cortés, Patricio Vargas
In this work, we investigate the relationship between the Seebeck coefficient $ (S)$ , and the differential entropy per particle (DEP, $ s$ ), as a tool for characterizing charge carriers in two-dimensional systems. Using armchair silicene nanoribbons as a model platform, we analyze how both quantities and their ratio depend on chemical potential at room temperature. While the Seebeck coefficient captures transport properties through the energy dependence of the electronic transmission, the DEP is directly connected to the system’s electronic entropy, offering a direct thermodynamic alternative for estimating $ S$ . We evaluate these transport-thermodynamic properties considering diverse ribbon widths, defining metallic and semiconducting regimes. We find both quantities $ S$ and $ s$ , are highly interconnected within the ribbon’s band gap energy region, and their ratio $ s/S$ converges to the elementary charge $ e$ across that energy window, fulfilling the Kelvin formula $ S=s/e$ . On the contrary, $ s/S$ is undefined for gapless ribbons in the energy window of the first transmission channel. These results establish the ratio between the DEP and the Seebeck coefficient as a reliable and complementary probe for the determination of the elementary charge, and to identify the cleanness of electronic band gaps as $ s/S$ matches with $ e$ .
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
9 pages, 7 figures
Suspended phase transitions: droplets trapped by solid films resist complete melting
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-08-22 20:00 EDT
Chenyu Jin, Guoxiang Chen, Beibei Wang, Hans Riegler
Melting is conventionally understood as a bulk first-order phase transition, where nucleation of the liquid phase is followed by rapid growth until the solid disappears. However, in thin crystalline films containing local heterogeneities, this process can be dramatically altered by interfacial forces. Here, we report experimental evidence of suspended melting in molecularly thin films of long-chain alkanes containing trapped liquid droplets. As temperature increases, these droplets expand and flatten, yet remain pinned within the surrounding solid layers, preventing full melting. The observed sensitivity of apparent contact angle to small temperature changes is explained by a theoretical model balancing bulk melting enthalpy and interfacial energies. This work highlights how melting in thin films can be frustrated and spatially arrested by local wetting constraints, revealing a rich interplay between phase transition dynamics, confinement, and interfacial topology. Beyond alkanes, these results suggest a generic mechanism by which melting, wetting, and film morphology conspire to locally suspend phase transitions.
Soft Condensed Matter (cond-mat.soft), Materials Science (cond-mat.mtrl-sci)
Equivariant Electronic Hamiltonian Prediction with Many-Body Message Passing
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-08-22 20:00 EDT
Chen Qian, Valdas Vitartas, James Kermode, Reinhard J. Maurer
Machine learning surrogates of Kohn-Sham Density Functional Theory Hamiltonians offer a powerful tool to accelerate the prediction of electronic properties of materials, such as electronic band structures and densities-of-states. For large-scale applications, an ideal model would exhibit high generalization ability and computational efficiency. Here, we introduce the MACE-H graph neural network, which combines high body-order message passing with a node-order expansion to efficiently obtain all relevant $ O(3)$ irreducible representations. The model achieves high accuracy and computational efficiency and captures the full local chemical environment features of, currently, up to $ f$ orbital matrix interaction blocks. We demonstrate the model’s accuracy and transferability on several open materials benchmark datasets of two-dimensional materials and a new dataset for bulk gold, achieving sub-meV prediction errors on matrix elements and eigenvalues across all systems. We further analyse the interplay of high body order message passing and locality that makes this model a good candidate for high-throughput material screening.
Materials Science (cond-mat.mtrl-sci)
15 pages, 8 figures
Microstructural and preliminary optical and microwave characterization of erbium doped CaMoO$_4$ thin films
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-08-22 20:00 EDT
Ignas Masiulionis, Bonnie Y.X. Lin, Sagar Kumar Seth, Gregory D. Grant, Wanda L. Lindquist, Sungjoon Kim, Junghwa Kim, Angel Yanguas-Gil, Jeffrey W. Elam, Jiefei Zhang, James M. LeBeau, David D. Awschalom, Supratik Guha
This work explores erbium-doped calcium molybdate (CaMoO$ _4$ ) thin films grown on silicon and yttria stabilized zirconia (YSZ) substrates, as a potential solid state system for C-band (utilizing the $ \sim$ 1.5 $ \mu$ m Er$ ^{3+}$ 4f-4f transition) quantum emitters for quantum network applications. Through molecular beam epitaxial growth experiments and electron microscopy, X-ray diffraction and reflection electron diffraction studies, we identify an incorporation limited deposition regime that enables a 1:1 Ca:Mo ratio in the growing film leading to single phase CaMoO$ _4$ formation that can be in-situ doped with Er (typically 2-100 ppm). We further show that growth on silicon substrates is single phase but polycrystalline in morphology; while growth on YSZ substrates leads to high-quality epitaxial single crystalline CaMoO$ _4$ films. We perform preliminary optical and microwave characterization on the suspected $ Y_1 - Z_1$ transition of 2 ppm, 200 nm epitaxial CaMoO$ _4$ annealed thin films and extract an optical inhomogeneous linewidth of 9.1(1) GHz, an optical excited state lifetime of 6.7(2) ms, a spectral diffusion-limited homogeneous linewidth of 6.7(4) MHz, and an EPR linewidth of 1.10(2) GHz.
Materials Science (cond-mat.mtrl-sci), Quantum Physics (quant-ph)
8 pages, 4 figures
Theoretical Study of Impurity Effects on Superconductivity in UTe2
New Submission | Superconductivity (cond-mat.supr-con) | 2025-08-22 20:00 EDT
Koki Doi, Shingo Haruna, Mutsuki Iwamoto, Takuji Nomura, Hirono Kaneyasu
This study investigates the impurity effects on UTe2 within the self-consistent Born approximation using the six-orbital f-d-p model which contains two uranium and tellurium atoms in the minimum unit cell. We analyze the dependence of superconducting transition temperature (Tc) on impurity concentration for various pairing symmetries proposed by experiments and theories. It clarifies that the decrease of Tc significantly depends on which atom sites the impurities reside. Particulalry, the analysis shows that the impurity at U-site has dominant effect on the change of Tc. Then, either the singlet state in the case of magnetic impurities or the triplet states in both non-magnetic and magnetic impurities are consistent with experiments. Thus, this indicates that elucidating the magnetic properties of impurities (i.e. magnetic or non-magnetic) is crucial for identifying the pairing symmetry of UTe2.
Superconductivity (cond-mat.supr-con)
Quantum-size effect induced Andreev bound states in ultrathin metallic islands proximitized by a superconductor
New Submission | Superconductivity (cond-mat.supr-con) | 2025-08-22 20:00 EDT
Guanyong Wang, Li-Shuo Liu, Zhen Zhu, Yue Zheng, Bo Yang, Dandan Guan, Shiyong Wang, Yaoyi Li, Canhua Liu, Wei Chen, Hao Zheng, Jinfeng Jia
While Andreev bound states (ABSs) have been realized in engineered superconducting junctions, their direct observation in normal metal/superconductor heterostructures-enabled by quantum confinement-remains experimentally elusive. Here, we report the detection of ABSs in ultrathin metallic islands (Bi, Ag, and SnTe) grown on the s-wave superconductor NbN. Using high-resolution scanning tunneling microscopy and spectroscopy, we clearly reveal in-gap ABSs with energies symmetric about the Fermi level. While the energies of these states show no position dependence, their wave functions exhibit spatial oscillations, demonstrating a quantum size effect. Both the energy levels and spatial distribution of the ABSs can be reproduced by our effective model in which a metallic island is coupled to the superconducting substrate via the proximity effect. We demonstrate that the coupling strength plays a critical role in determining the ABS energies. Our work introduces a novel physical platform for implementing ABSs, which hold promise for significant device applications.
Superconductivity (cond-mat.supr-con), Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Materials Science (cond-mat.mtrl-sci)
Physical Review Letters 135, 076201 (2025)
Unraveling Shear Strain Induced Ferroelectric-to-Antiferroelectric Phase Transition and Accessing Intrinsic Antiferroelectricity in Two-dimensional NbOCl2
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-08-22 20:00 EDT
Jiawei Mao, Yinglu Jia, Gaoyang Gou, Shi Liu, Xiao Cheng Zeng
Compared to the well studied two-dimensional (2D) ferroelectricity, much rare is the appearance of 2D antiferroelectricity, where local dipoles from the nonequivalent sublattices within 2D monolayers are oppositely orientated. Using NbOCl2 monolayer with competing ferroelectric (FE) and antiferroelectric (AFE) phases as a 2D material platform, we demonstrate the emerging of intrinsic antiferroelectricity in NbOCl2 monolayer under the experimentally accessible shear strain, and new functionality associated with electric field induced AFE-to-FE phase transition. Specifically, the complex configuration space accommodating FE and AFE phases, polarization switching kinetics and finite temperature thermodynamic properties of 2D NbOCl2, are all accurately predicted by large-scale molecular dynamic (MD) simulations based on deep learning interatomic potential (DP) model. Moreover, room temperature stable antiferroelectricity with low polarization switching barrier and one-dimensional (1D) collinear polarization arrangement is predicted in shear deformed NbOCl2 monolayer. Transition from AFE to FE phase in 2D NbOCl2 can be triggered by the low critical electric field, leading to the double polarization-electric (P-E) loop with small hysteresis. A new type optoelectronic device composed of AFE-NbOCl2, enabling electric “writing” and nonlinear optical “reading” logical operation with fast operation speed and low power consumption is also proposed.
Materials Science (cond-mat.mtrl-sci)
Marangoni swimmer pushing particle raft under 1D confinement
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-08-22 20:00 EDT
Abhradeep Maitra, Anupam Pandey, Sebastien Michelin, Sunghwan Jung
Active matter systems, due to their spontaneous self-propulsion ability, hold potential for future applications in healthcare and environmental sustainability. Marangoni swimmers, a type of synthetic active matter, are a common model system for understanding the underlying physics. Existing studies of the interactions of active matter with passive particles have mostly focused on the modification of the behavior of the passive particles. In contrast, we analyse here experimentally the impact on the self-propulsion of camphor-infused agarose disks (active) of their interactions with floating hollow glass microspheres (passive) within an annular channel. Two distinct regimes are observed: a steady regime with uni-directional motion of the swimmer at low packing fractions (\phi_{\textrm{ini}} \lesssim 0.45) and an oscillatory regime with to-and-fro motion at higher packing fractions (\phi_{\textrm{ini}} \gtrsim 0.45). In the former, the swimmer pushes nearly the entire particle raft together with it, like a towing cargo, causing a decrease in swimmer speed with increasing packing fraction due to the additional drag from the particle raft. A simplified force-balance model is finally proposed that captures the experimental trend in swimmer speed reasonably well.
Soft Condensed Matter (cond-mat.soft)
27 pages, 7 figures and a Supplementary information file
Obstacle-tuned transition from chaotic to coherent vortex flows and odd diffusion in chiral active fluids
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-08-22 20:00 EDT
Joscha Mecke, Yongxiang Gao, Marisol Ripoll
The interaction of a suspension of rotating colloids with a periodically patterned structure is here investigated by means of continuum theoretical predictions and hydrodynamic simulations. Close to the obstacle surface, rotors circulate opposite to their inherent direction of rotation as a result of unidirectional rotational stresses, which is in agreement with a prediction of the generalised Stokes equation. The resulting stationary background flow significantly affects the system dynamics and coexists with the intrinsic active turbulent behaviour. The relative importance of either of the two contributions can be controlled with the rotor density and the obstacle size, such that the system is either dominated by stationary vortices pinned to the obstacles or vivid active turbulent dynamics. While momentum dissipation into an underlying frictional substrate damps the related flows, small values of the friction can enhance the vortex flow around an obstacle. The colloids’ diffusive dynamics are governed by odd diffusive fluxes guiding the colloids around the excluded volume introduced by obstacles, such that enhanced effective diffusive transport is obtained at finite obstruction. Our results pave the way to systematically address how confinement can be employed in order to control or harness the dynamics of colloidal chiral active turbulence and how the interplay of emerging edge currents and active turbulent dynamics at varying densities can be systematically determined.
Statistical Mechanics (cond-mat.stat-mech), Computational Physics (physics.comp-ph), Fluid Dynamics (physics.flu-dyn)
Microphases in Active Brownian Particle Systems Lead to Collective Motion
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-08-22 20:00 EDT
Cheng Yang, Qiandong Dai, Shun Xu, Xin Zhou
Active matter can consume energy to generate active forces that propel themselves and to exhibit numerous fascinating out-of-equilibrium features. The paradigmatic model, active Brownian particles, even without attractive and alignment interactions, can form a phase coexistence of low- and high-density phases. Recent researches have revealed that particles within the high-density phase move in a coordinated manner, creating either aligned or vortex-like velocity-correlation domains. However, the mechanism underlying the translation or rotation of these domains remains unclear. In this study, we demonstrate that the velocity-correlation domains are spatially consistent with the ordered microphases. The microphases, surrounded by defects, are hexatic and differently oriented microdomains. The direction of particles’ active forces at the edge of a microphase tends to point inward, creating compression that maintains this microphase. The net active force or active torque acting on the microphase causes it to translate or rotate, thereby generating the velocity-correlation domains.
Soft Condensed Matter (cond-mat.soft)
Multiple crossover in the decay of metastable volume fraction of a Blume-Capel ferromagnetic needle
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-08-22 20:00 EDT
Ishita Tikader, Muktish Acharyya
The transient behaviours of a Blume-Capel ferromagnetic needle have been studied extensively by Monte-Carlo simulation. The needle has an elongated length in one direction compared to its cross-section. In the context of transient behaviour, we have captured the decay of the metastable state and the magnetic relaxation behaviours in our study. The dependence of metastable behaviour with anisotropy (single site) has been studied. \emph{Interestingly, we have observed multiple (different values of $ n$ in different time domains) crossover in the decay of metastable volume fraction (obeying Avrami’s law $ \beta \sim {\rm exp}(-Kt^n)$ ). We have identified the crossover time, and the values of $ n$ are estimated precisely.} The mean (magnetic) reversal time has been studied as a function of anisotropy. It is observed to be almost independent of anisotropy for its negative value; however, it is found to decrease exponentially with positive anisotropy. The exponential relaxation behaviour (in the corresponding paramagnetic phase) is observed. The range of the relaxation time is observed to decrease as the temperature increases.
Statistical Mechanics (cond-mat.stat-mech)
10 Pages Latex, 12 captioned figures, 5 Tables
A rutile-based homologous series Na(PtO$2$)${2\it{n}+1}$ discovered by computationally assisted high-pressure synthesis
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-08-22 20:00 EDT
Yasuhito Kobayashi, Hidefumi Takahashi, Shunsuke Kitou, Akitoshi Nakano, Hajime Sagayama, Yuichi Yamasaki, Shintaro Ishiwata
Layered transition metal oxides typified by the Ruddlesden-Popper phase have been extensively studied for its applications in high-temperature superconductivity, catalysis, and battery technologies. Despite the remarkable structural diversity and catalytic functionality of platinum oxides, the exploration of layered polymorphs has remained significantly constrained mainly due to the high inertness of platinum. Here, we discover a new homologous series of layered ternary oxides, Na(PtO$ _2$ )$ _{2\it{n}+1}$ , by a combination of highly oxidizing high-pressure methods and density functional theory (DFT) calculations. This series features unprecedented layered structural motifs, rutile-based PtO$ _6$ octahedra and one-dimensional PtO$ _4$ square-planar columns, which enables systematic control of dimensionality. Furthermore, we demonstrate a computationally-assisted identification of isomeric and putative members of this homologous series as confirmed by controlled synthesis and quantitative analysis of diffuse scattering data. This approach provides an effective platform for the exhaustive exploration of metastable transition metal oxides with rich structural variations.
Materials Science (cond-mat.mtrl-sci), Strongly Correlated Electrons (cond-mat.str-el)
Radio-Frequency Quantum Rectification in Kagome Superconductor CsV3Sb5
New Submission | Superconductivity (cond-mat.supr-con) | 2025-08-22 20:00 EDT
Han-Xin Lou, Jing-Jing Chen, Xing-Guo Ye, Zhen-Bing Tan, An-Qi Wang, Qing Yin, Xin Liao, Jing-Zhi Fang, Xing-Yu Liu, Yi-Lin He, Zhen-Tao Zhang, Chuan Li, Zhong-Ming Wei, Xiu-Mei Ma, Dapeng Yu, Zhi-Min Liao
Rectification of electromagnetic fields into direct current (DC) is pivotal for energy harvesting, wireless charging, and next-generation communication technologies. The superconducting diode effect, which exploits the nonreciprocal transport of dissipationless superconducting currents, offers ultra-low power consumption and high rectification ratios. Combining the superconducting diode effect with the AC Josephson effect holds promise for converting radio-frequency (rf) irradiation into a quantized DC output. However, experimental realization has been hindered by challenges in achieving the necessary symmetry breaking and fabricating high-performance Josephson junctions. Here we demonstrate the quantum rectification in kagome superconductor CsV3Sb5, which hosts emergent Josephson effects and a zero-field Josephson diode. Under rf irradiation, a DC voltage emerges without applied bias, scaling linearly with frequency as V = hf/2e, where h is Planck’s constant, f is the microwave frequency, and e is the electron charge. Furthermore, the rectified voltage exhibits quantized steps with increasing rf power, consistent with Shapiro step quantization. Our work establishes CsV3Sb5 as a versatile platform for wireless quantum power supplies and charging, and underscores the intertwined order parameters as a promising pathway for precise quantum matter control.
Superconductivity (cond-mat.supr-con)
39 pages, 14 figures
Electron-Hole Crossover in $\mathrm{La}{3-x}\mathrm{Sr}{x}\mathrm{Ni}{2}\mathrm{O}{7-δ}$ Thin Films
New Submission | Superconductivity (cond-mat.supr-con) | 2025-08-22 20:00 EDT
Maosen Wang, Bo Hao, Wenjie Sun, Shengjun Yan, Shengwang Sun, Hongyi Zhang, Zhengbin Gu, Yuefeng Nie
The ambient-pressure superconductivity in $ \mathrm{La}{3}\mathrm{Ni}{2}\mathrm{O}{7}$ thin films via compressive epitaxial strain provides a highly accessible platform for diverse characterization techniques, facilitating the studies of high-temperature superconductivity. Here, we systematically map the superconducting dome in compressively strained $ \mathrm{La}{3-x}\mathrm{Sr}{x}\mathrm{Ni}{2}\mathrm{O}{7-\delta}$ thin films by simultaneously tuning Sr doping and oxygen content and reveal an electron-hole crossover associated with the maximum transition temperature ($ {T}{c}$ ). This electron-hole crossover, marked by an anomalous sign change in the Hall coefficient ($ {R}{H}$ ), is reminiscent of electron-doped cuprates, which may signal a Fermi surface reconstruction. Beyond the superconducting dome, a $ \ln1/T$ insulating regime and a $ T$ -linear resistivity regime are also resolved, resembling behaviors observed in cuprates and infinite-layer nickelates. This work reveals a dome-shaped relationship between $ {T}{c}$ and $ {R}_{H}$ and establishes a key framework for understanding unconventional superconductivity in nickelate systems.
Superconductivity (cond-mat.supr-con), Materials Science (cond-mat.mtrl-sci), Strongly Correlated Electrons (cond-mat.str-el)
32 pages, 15 figures
Flow Matching at Scale: A Machine Learning Framework for Efficient Large-Size Sampling of Many-Body Systems
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-08-22 20:00 EDT
We propose a machine learning framework based on Flow Matching to overcome the scaling limitations of Markov Chain Monte Carlo (MCMC) methods. We demonstrate its capability in the 2D XY model, where a single network, trained only on configurations from a small ($ 32\times 32$ ) lattice at sparse temperature points, generates reliable samples for a significantly larger system ($ 128\times 128$ ) across a continuous temperature range without retraining. The generated configurations show strong agreement with key thermodynamic observables and correctly capture the signatures of the Berezinskii-Kosterlitz-Thouless (BKT) transition. This dual generalization is enabled by the Flow Matching framework, which allows us to learn a continuous, temperature-conditioned mapping. At the same time, the inductive biases of the underlying CNN architecture ensure that the learned local physical rules are scale-invariant. This “train-small, generate-large” capability establishes a new paradigm for efficiently studying critical phenomena, offering a significant computational advantage for exploring the thermodynamic limit. The method can be directly applied to other classical or quantum many-body systems described by continuous fields on a lattice.
Statistical Mechanics (cond-mat.stat-mech), Machine Learning (cs.LG)
Topological potentials guiding protein self-assembly
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-08-22 20:00 EDT
Ivan Spirandelli, Dmitriy Morozov, Arnur Nigmetov, Myfanwy E. Evans
The simulated self-assembly of molecular building blocks into functional complexes is a key area of study in computational biology and materials science. Self-assembly simulations of proteins, driven by short-range non-polar interactions, can find the biologically correct assembly as the energy minimizing state. Short-ranged potentials produce rugged energy landscapes however, which lead to simulations becoming trapped in non-functional, local minimizers.
Successful self-assembly simulations depend both on the physical realism of the driving potentials as well as their ability to efficiently explore the configuration space.
We introduce a long-range topological potential, quantified via weighted total persistence, and combine it with the morphometric approach to solvation-free energy. This combination improves the assembly success rate in simulations of the tobacco mosaic virus dimer and other protein complexes by up to sixteen-fold compared with the morphometric model alone. It further enables successful simulation in systems that don’t otherwise assemble during the examined timescales.
Compared to previous topology-based work, which has been primarily descriptive, our approach uses topological measures as an active energetic bias that is independent of electrostatics or chemical specificity and depends only on atomic coordinates. Therefore the method can, in principle, be applied to arbitrary systems where such coordinates are optimized. Integrating topological descriptions into an energy function offers a general strategy for overcoming kinetic barriers in molecular simulations, with potential applications in drug design, materials development, and the study of complex self-assembly processes.
Soft Condensed Matter (cond-mat.soft), Computational Geometry (cs.CG), Algebraic Topology (math.AT)
19 pages, 6 figures
The effect of multi-occupancy traps on the diffusion and retention of multiple hydrogen isotopes in irradiated tungsten and vanadium
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-08-22 20:00 EDT
Sanjeet Kaur, Daniel R. Mason, Prashanth Srinivasan, Stephen Dixon, Sid Mungale, Teresa Orr, Mikhail Yu. Lavrentiev, Duc Nguyen-Manh
We propose a computational scheme for the diffusion and retention of multiple hydrogen isotopes (HI) with multi-occupancy traps parameterized by first principles calculations. We show that it is often acceptable to reduce the complexity of the coupled differential equations for gas evolution by taking the dynamic steady state, a generalisation of the Oriani equilibrium for multiple isotopes and multi-occupancy traps. The effective gas diffusivity varies most with mobile fraction when the total gas concentration approximates the trap density. We show HI binding to a monovacancy in vanadium produces a non-monotonic dependence between diffusivity and gas concentration, unlike the tungsten system. We demonstrate the difference between multiple single occupancy traps and multi-occupancy traps in long-term diffusion dynamics. The applicability of the multi-occupancy, multi-isotope model in steady state is assessed by comparison to an isotope exchange experiment between hydrogen and deuterium in self-ion irradiated tungsten. The vacancy distribution is estimated with molecular dynamics, and the retention across sample depth shows good agreement with experiment using no fitting parameters.
Materials Science (cond-mat.mtrl-sci)
16 pages, 9 figures
Role of Ward-Takahashi identity in an electron-phonon coupled system – Revisiting phonon shift current
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-08-22 20:00 EDT
Takahiro Morimoto, Naoto Nagaosa
We study bulk photovoltaic effects in electron-phonon coupled systems. The conservation of current or gauge invariance, manifested as the Ward-Takahashi identity, plays an essential role in the analysis of the Feynman diagrams, and the leading order contribution to the phonon shift current is identified accordingly. The leading order contribution essentially arises from the electric polarization carried by optically excited phonons, where the shift current is generated due to a change of electric polarization in the steady state under the optical excitation of phonons.
Strongly Correlated Electrons (cond-mat.str-el)
11 pages, 2 figures
Analytical Theory of Chiral Active Particle Transport in a Fluctuating Density Field
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-08-22 20:00 EDT
We develop a closed-form analytical theory for the transport of a chiral active Brownian particle (cABP) in three dimensions, moving through a fluctuating local density field that coarse-grains steric and dynamical interactions in a dense active medium. The density field is modeled as an Ornstein–Uhlenbeck process with finite correlation time $ \tau$ and fluctuation strength $ \sigma_\rho^2$ , capturing both spatial variations and temporal memory. Within this framework, we derive exact expressions for the mean-squared displacement (MSD) and time-dependent diffusivity, showing how chirality and density coupling renormalize orientational persistence and generate dynamical crossovers. The theory predicts: (i) anomalously high initial diffusivity in denser regions, arising from a transient drift driven by local swim-pressure gradients; (ii) a finite crossover time $ t_c$ for homogenizing density inhomogeneities, with steady-state diffusivity retaining memory of the initial environment; (iii) a non-monotonic $ t_c(\Omega)$ with a global minimum at intermediate chirality, and a three-regime suppression of $ D_\infty(\Omega)$ consistent with clustered phases in simulations; and (iv) a resonance-like peak in early-time oscillatory transport at an optimal chirality $ \Omega^\ast$ . The framework reproduces known scaling of $ D_\infty$ with activity and chirality, while uncovering new memory effects and chirality-controlled optimal transport, offering predictive insight for biological circle swimmers and active metamaterials.
Statistical Mechanics (cond-mat.stat-mech)
Constrained Random Phase Approximation: the spectral method
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-08-22 20:00 EDT
Merzuk Kaltak, Alexander Hampel, Martin Schlipf, Indukuru Ramesh Reddy, Bongae Kim, Georg Kresse
We present a new constrained Random Phase Approximation (cRPA) method, termed spectral cRPA (s-cRPA), and compare it to established cRPA approaches for Scandium and Copper by varying the 3d shell filling. The s-cRPA consistently yields larger Hubbard $ U$ interaction values. Applied to the realistic system CaFeO$ _3$ , s-cRPA produces interaction parameters significantly closer to those required within DFT+$ U$ to induce the experimentally observed insulating state, overcoming the metallic behavior predicted by standard density functionals. We also address the issue of negative interaction values found in the projector cRPA method for filled d-shells, demonstrating that s-cRPA offers superior numerical stability through electron conversion. Overall, s-cRPA is more robust and effectively overcomes the known underestimation of $ U$ in standard cRPA, making it a promising tool for the community. Additionally, we have enhanced our implementation with features for computing multi-center interactions to analyze spatial decay and developed a low-scaling variant with a compressed Matsubara grid to efficiently obtain full frequency-dependent interactions.
Strongly Correlated Electrons (cond-mat.str-el), Other Condensed Matter (cond-mat.other), Atomic and Molecular Clusters (physics.atm-clus), Computational Physics (physics.comp-ph), Quantum Physics (quant-ph)
12 pages, 5 figures, to be published in Physical Review B, Poster presented at PSI-K, Lausanne (August 2025). Talk given at Workshop “The determination of Hubbard parameters: progress, pitfalls, and prospects”, Gandia (September 2025)
Strong lead-free bioinspired piezoceramics for durable energy transducers
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-08-22 20:00 EDT
Ruxue Yang, Temesgen Tadeyos Zate, Soumyajit Mojumder, Oriol Gavalda-Diaz, Zihe Li, Ajeet Kumar, James Roscow, Hamideh Khanbareh, Astri Bjørnetun Haugen, Florian Bouville
Durable, high-performance and eco-friendly lead-free piezoceramics are essential for next-generation sustainable energy transducers and electromechanical systems. While significant performance enhancements have been made, through chemical composition, texture, or crystal defects, piezoceramics are intrinsically weak mechanically, which negatively impact their working conditions and durability. What’s more, improving comprehensive mechanical durability without sacrificing piezoelectric performance remains a key challenge. Here, we design bioinspired Bi0.5Na0.5TiO3 (BNT) ceramics using a scalable colloidal process that enables multiscale control over the microstructure. The design comprises plate-like monocrystalline BNT bricks stacked to induce a crystallographic texture along the poling direction, bonded together by a silica-based mortar, forming the brick-and-mortar phase. This deliberate microstructure design yields 2- to 3-fold increase in flexural strength, and 1.6- to 2-fold increase in fracture toughness compared with a BNT synthesized conventionally, comparable to common structural ceramics, without sacrificing the piezoelectric performance. In addition, the bioinspired BNT exhibit dramatically enhanced ferroelectric fatigue resistance, with a 40- to 600-folds improvement in the number of field-induced electromechanical cycles before failure. These gains stem from residual stress fields generated at the interface between silica pockets and BNT bricks, which delay crack initiation. Furthermore, we demonstrated enhanced transducing capability and electromechanical fatigue resistance using a cantilever beam-based piezoelectric transducer under bending mode. Given its non-chemical-compositional origin, this bioinspired strategy could be broadly applicable to other piezoelectric material systems for applications where both functional and structural performance are critical.
Materials Science (cond-mat.mtrl-sci), Applied Physics (physics.app-ph)
Bending nanoribbon to induce large anisotropic magnetoconductance
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-08-22 20:00 EDT
Ponder Liu, Hao-Cheng Hung, You-Ting Huang, Jia-Cheng Li, Carmine Ortix, Ching-Hao Chang
When a nanoribbon is bent under a homogeneous external magnetic field, the effective magnetic field inside becomes either homogeneous or inhomogeneous, depending on the direction of the field. This enables the selective creation of bulk, interface, and edge magnetic states in the bent structure, for a magnetic field with a strength. We establish theoretically that these tuneable states lead to a strong geometry-induced anisotropic magnetoconductance (GAMC) in perpendicularly bent nanoribbon, which can reach up to 100%. Moreover, the GAMC can be further enhanced to 200%, 300%, or even higher by either further bending or tuning the bending angle. The potential of this phenomenon for practical applications is demonstrated by its stable anisotropy, which remains consistent across a wide range of Fermi energies, can be observed even at weak magnetic fields and room temperature, and occurs in various systems such as two-dimensional electron gas (2DEG) and graphene.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Spontaneous nonreciprocal transport in a gate-tunable ferromagnetic Rashba 2-dimensional electron gas
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-08-22 20:00 EDT
Gabriel Lazrak, Radu Abrudan, Borge Göbel, David Hrabovsky, Chen Luo, Victor Ukleev, Srijani Mallik, Luis M. Vicente-Arche, Florin Radu, Sergio Valencia, Annika Johansson, Agnès Barthélémy, Manuel Bibes
The broken inversion symmetry at interfaces of complex oxides gives rise to emergent phenomena, including ferromagnetism and Rashba spin-orbit coupling (SOC), which profoundly influence the electronic structure by entangling spin and momentum. While the interplay between Rashba SOC and ferromagnetism is theoretically intriguing, its experimental manifestations remain largely unexplored. Here, we demonstrate that ferromagnetic 2DEGs at SrTiO$ _3$ -based interfaces exhibit spontaneous nonreciprocal transport - a distinctive hallmark of Rashba ferromagnets - even in the absence of an external magnetic field. This nonreciprocal response, along with clear signatures of ferromagnetism such as anisotropic magnetoresistance and the anomalous Hall effect (AHE), is strongly tunable by gate voltage. Remarkably, the AHE not only varies in amplitude but even reverses sign, reflecting a subtle interplay between Fermi level position and Berry curvature distribution. These results establish SrTiO$ _3$ 2DEGs as a model platform for studying Rashba ferromagnetism and demonstrate active control over transport phenomena in time- and inversion-symmetry-broken systems, paving the way for gate-tunable spintronic devices.
Strongly Correlated Electrons (cond-mat.str-el), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Casimir versus Helmholtz fluctuation induced force in { the Nagle}-Kardar model: Exact results
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-08-22 20:00 EDT
Daniel Dantchev, Nicholay S. Tonchev, Joseph Rudnick
When used to describe \textit{finite} systems the {conjugate} statistical-mechanical ensembles are \textit{not} equivalent. This has physical implications for the behavior of the fluctuation induced forces pertinent to the different ensembles. Here, {we study the Nagle-Kardar model within the grand-canonical ensemble (GCE) and the canonical ensemble (CE) (with conserved total magnetization) for periodic boundary conditions (PBC)}. {We focus on two fluctuation-induce forces: the Casimir force (CF) in the GCE and the Helmholtz force (HF) in the CE}. In the infinite system limit the model exhibits a critical line, which ends at a tricritical point. Unexpectedly, the critical Casimir force (CCF) is \textit{repulsive} near the critical line and tricritical point, decaying rapidly upon departure from those two regions and becoming \textit{attractive}. This violates the widely-accepted ``boundary condition rule,’’ which presumes that the CCF is attractive for equivalent boundary conditions (BC) and repulsive for conflicting BC. For the HF we find that it also changes sign as a function of temperature and the magnetization. We conclude, that CCF and HF have a behavior quite different from each other as a function of the tunable parameters (temperature, magnetic field, or magnetization) of the model. This dependence allows {for the control of the} \textit{sign} of these forces, as well as their magnitude.
Statistical Mechanics (cond-mat.stat-mech)
8 pages, 4 figures
Quantum Geometric Renormalization of the Hall Coefficient and Unconventional Hall Resistivity in ZrTe5
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-08-22 20:00 EDT
Huimin Xie, Bo Fu, Huan-Wen Wang, Wenyu Shan, Shun-Qing Shen
The anomalous Hall effect (AHE), conventionally associated with time-reversal symmetry breaking in ferromagnetic materials, has recently been observed in nonmagnetic topological materials, raising questions about its origin. We unravel the unconventional Hall response in the nonmagnetic Dirac material ZrTe5, known for its massive Dirac bands and unique electronic and transport properties. Using the Kubo-Streda formula within the Landau level framework, we explore the interplay of quantum effects induced by the magnetic field (B) and disorder across the semiclassical and quantum regimes. In the semiclassical regime, the Hall resistivity remains linear in the magnetic field, but the Hall coefficient will be renormalized by the quantum geometric effects and electron-hole coherence, especially at low carrier densities where the disorder scattering dominates. In quantum limit, the Hall conductivity exhibits an unsaturating 1/B scaling. As a result, the transverse conductivity dominates transport in the ultra-quantum limit, and the Hall resistivity crosses over from B to B^{-1} dependence as the system transitions from the semiclassical regime to the quantum limit. This work elucidates the mechanisms underlying the unconventional Hall effect in ZrTe5 and provides insights into the AHE in other nonmagnetic Dirac materials as well.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
23 pages, 4 figures. Comments are welcomed
Rotating Spin Wave Modes in Nanoscale Möbius Strips
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-08-22 20:00 EDT
Ashfaque Thonikkadavan, Massimiliano d’Aquino, Riccardo Hertel
Curved and topologically nontrivial magnetic structures offer new pathways to control spin-wave behavior beyond planar geometries. Here, we study spin-wave dynamics in Möbius-shaped soft-magnetic nanostrips using micromagnetic simulations. By comparing single-, double-, and triple-twisted Möbius strips to a topologically trivial bent ring, we isolate the roles of helical twist and non-orientable topology. Möbius geometries exhibit non-degenerate mode doublets associated with counterpropagating spin waves, in contrast to the standing-wave doublets in the trivial case. This splitting arises from a twist-induced geometric (Berry) phase that breaks propagation symmetry, producing non-reciprocal dispersion relations. The Möbius topology further imposes antisymmetric boundary conditions, resulting in half-integer wavelength quantization. Local RF excitation allows for the selective generation of spin waves with defined frequency and direction. An analytical model reproduces the dispersion behavior with excellent agreement. These results highlight how geometric and topological design can be leveraged to engineer spin-wave transport in three-dimensional magnonic systems.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
9 pages, 8 figures
Competition Between Controllable Non-Radiative and Intrinsic Radiative Second-Order Recombination in Halide Perovskites
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-08-22 20:00 EDT
Dengyang Guo, Alan R. Bowman, Sebastian Gorgon, Changsoon Cho, Youngkwang Jung, Jiashang Zhao, Linjie Dai, Jaewang Park, Kyung Mun Yeom, Satyawan Nagane, Stuart Macpherson, Weidong Xu, Jun Hong Noh, Sang Il Seok, Tom Savenije, Samuel D. Stranks
Halide perovskite solar cells have demonstrated a rapid increase in power conversion efficiencies. Understanding and mitigating remaining carrier losses in halide perovskites is now crucial to enable further increases to approach their practical efficiency limits. Whilst the most widely known non-radiative recombination from solar cells relates to carrier trapping and is first order in carrier density, recent reports have revealed a non-radiative pathway that is second order. However, the origin and impact of this second-order process on devices remain unclear. Here, we understand this non-radiative second-order recombination (k2non) pathway by manipulating the charge carrier dynamics via controlling the bulk and surface conditions. By combining temperature-dependent spectroscopies, we demonstrate that the value of k2non depends on extrinsic factors, in contrast to intrinsic second-order recombination, which aligns with theoretical evaluations through van Roosbroeck-Shockley relations. Based on density functional theory simulations and Quasi-Fermi level calculations, we propose that shallow surface states are the primary origin of this second-order non-radiative component, contributing up to ~80 mV of the overall reduction in Voc at room temperature. This work reveals that carrier losses from two non-radiative recombination types (first and second order) are not linked, emphasizing the need for distinctive mitigation strategies targeting each type to unlock the full efficiency potential of perovskite solar cells.
Materials Science (cond-mat.mtrl-sci)
Polymer translocation through extended patterned pores: scaling of the total translocation time
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-08-22 20:00 EDT
Andri Sharma, Abhishek Chaudhuri, Rajeev Kapri
We study the translocation of a flexible polymer through extended patterned pores using molecular dynamics (MD) simulations. We consider cylindrical and conical pore geometries that can be controlled by the angle of the pore apex $ \alpha$ . We obtained the average translocation time $ \langle \tau \rangle$ for various chain lengths $ N$ and the length of the pores $ L_p$ for various values $ \alpha$ and found that $ \langle \tau \rangle$ scales as $ \langle \tau \rangle \sim N^\gamma \mathcal{F}\left( L_p N^\phi \right)$ with exponents $ \gamma = 3.00\pm0.05$ and $ \phi = 1.50\pm0.05$ for both patterned and unpatterned pores.
Soft Condensed Matter (cond-mat.soft)
8 pages, 7 figures
Surface separation in elastoplastic contacts
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-08-22 20:00 EDT
Andreas Almqvist, Bo N. J. Persson
Understanding the contact between rough surfaces undergoing plastic deformation is crucial in many applications. We study the effect of plastic deformation on the surface separation between two solids with random roughness. Assuming a constant penetration hardness, we propose a procedure within Persson’s multiscale contact mechanics theory to obtain the average surface separation by applying the elastic formulation to an effective power spectrum that accounts for plastic smoothing. Deterministic numerical simulations based on the boundary element method are used to validate the procedure and show good agreement with the theoretical predictions. The treatment also provides a route to incorporate plastic stiffening of the roughness as the stress state becomes increasingly hydrostatic at large plastic deformation.
Soft Condensed Matter (cond-mat.soft)
Attention-Based Explainability for Structure-Property Relationships
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-08-22 20:00 EDT
Boris N. Slautin, Utkarsh Pratiush, Yongtao Liu, Hiroshi Funakubo, Vladimir V. Shvartsman, Doru C. Lupascu, Sergei V. Kalinin
Machine learning methods are emerging as a universal paradigm for constructing correlative structure-property relationships in materials science based on multimodal characterization. However, this necessitates development of methods for physical interpretability of the resulting correlative models. Here, we demonstrate the potential of attention-based neural networks for revealing structure-property relationships and the underlying physical mechanisms, using the ferroelectric properties of PbTiO3 thin films as a case study. Through the analysis of attention scores, we disentangle the influence of distinct domain patterns on the polarization switching process. The attention-based Transformer model is explored both as a direct interpretability tool and as a surrogate for explaining representations learned via unsupervised machine learning, enabling the identification of physically grounded correlations. We compare attention-derived interpretability scores with classical SHapley Additive exPlanations (SHAP) analysis and show that, in contrast to applications in natural language processing, attention mechanisms in materials science exhibit high efficiency in highlighting meaningful structural features.
Materials Science (cond-mat.mtrl-sci)
34 pages, 12 figures
On-the-fly electrical readout of individual skyrmion dynamics by anomalous Hall effect, correlated with real-time Kerr microscopy
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-08-22 20:00 EDT
Grischa Beneke, Kilian Leutner, Nikhil Vijayan, Fabian Kammerbauer, Duc Minh Tran, Sachin Krishnia, Johannes Güttinger, Armin Satz, Robert Frömter, Mathias Kläui
Magnetic skyrmions, topologically stabilized spin textures, are promising candidates for future memory devices and non-conventional computing applications due to their enhanced stability, non-linear interactions, and low-power manipulation capabilities. Despite their significant potential, the reliable electrical readout of individual skyrmions remains a fundamental challenge. While magnetic tunnel junctions and anomalous-Hall-effect-based techniques have demonstrated skyrmion detection capabilities, they currently fail to reliably detect single moving skyrmions as required for applications. Our approach leverages thermally activated skyrmions, where a low constant drive current simultaneously generates both skyrmion motion and the Hall voltage necessary for detection. We demonstrate the reliability of this method through real-time correlation between measured Hall voltage signals and direct Kerr microscopy imaging. Two consecutive Hall crosses allow for determining the skyrmion velocity, in accordance to Kerr microscopy videos. These advances establish a robust platform for skyrmion-based sensors, counters and unconventional computing systems that depend on precise individual skyrmion control and detection.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Applied Physics (physics.app-ph)
10 pages, 4 figures
Revisiting thermal transport in CuCl: First-principles calculations and machine learning force fields
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-08-22 20:00 EDT
Ashis Kundu, Florian Knoop, Igor A. Abrikosov
Accurate prediction of lattice thermal conductivity ($ \kappa_l$ ) in strongly anharmonic materials requires renormalized interatomic force constants (IFCs) and appropriate incorporation of diagonal and off-diagonal contributions and higher-order scattering. We investigate CuCl, a highly anharmonic system with a simple zincblende structure and ultralow $ \kappa_l$ . Our calculations, including IFC renormalization and four-phonon scattering, show excellent agreement with the experiment, underscoring the critical role of both effects in the accurate estimation of $ \kappa_l$ . Furthermore, the unusual pressure dependence of $ \kappa_l$ is explored using a rigorously validated machine-learned force field, with the predicted values showing good agreement with the experimentally observed trend of monotonic decrease. This behavior is primarily driven by a significant increase in four-phonon scattering and a reduction in the group velocity of transverse acoustic modes. Overall, this study establishes a robust framework for modeling thermal transport in strongly anharmonic materials.
Materials Science (cond-mat.mtrl-sci)
9 pages, 9 figures
NMR evidence for an antisite-induced magnetic moment on Bi in a topological insulator heterostructures MnBi2Te4/(Bi2Te3)n
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-08-22 20:00 EDT
R. Kalvig, E. Jedryka, A. Lynnyk, P. Skupinski, K. Grasza, M. Wojcik
MnBi2Te4 (MBT) is the first intrinsic magnetic topological insulator, combining a topologically protected surface metallic state and intrinsic magnetic order. A structural compatibility with the nonmagnetic Bi2Te4 (BT) parent compound gives a possibility to create MBT/BT heterostructures and manipulate their magnetic state in view of optimizing the Quantum Anomalous Hall Effect (QAHE). In this work an extensive NMR study, supported by the bulk magnetization measurements has been performed at 4.2 K on a self-organized single crystal MnBi2Te4(Bi2Te4)n heterostructure. 55Mn and 209Bi NMR signal have been recorded as a function of the out-of-plane magnetic field up to 6T, covering a spin-flop transition from the antiferromagnetic (AFM) to the canted antiferromagnetic (CAFM) configuration of the Mn layers. Structural defects were shown to contribute a small ferromagnetic component below the spin-flop field. Presence of the AFM-coupled Mn antisites has been evidenced and shown to induce an antiparallel magnetic moment on Bi atoms within the host Bi layer. Detection of the induced magnetic moment on bismuth which contributes a new ferromagnetic component is of utmost importance for understanding the magnetic interactions in the MBT/BT system. These findings have potentially important implications for engineering the QAH devices.
Materials Science (cond-mat.mtrl-sci)
5 pages, 3 figures
Accurate complex-stacking-fault Gibbs energy in Ni3Al at high temperatures
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-08-22 20:00 EDT
Xiang Xu, Xi Zhang, Andrei Ruban, Siegfried Schmauder, Blazej Grabowski
To gain a deeper insight into the anomalous yield behavior of Ni3Al, it is essential to obtain temperature-dependent formation Gibbs energies of the relevant planar defects. Here, the Gibbs energy of the complex stacking fault (CSF) is evaluated using a recently proposed ab initio framework [Acta Materialia, 255 (2023) 118986], accounting for all thermal contributions - including anharmonicity and paramagnetism - up to the melting point. The CSF energy shows a moderate decrease from 300K to about 1200 K, followed by a stronger drop. We demonstrate the necessity to carefully consider the individual thermal excitations. We also propose a way to analyze the origin of the significant anharmonic contribution to the CSF energy through atomic pair distributions at the CSF plane. With the newly available high-temperature CSF data, an increasing energy barrier for the cross-slip process in Ni3Al with increasing temperature is unveiled, necessitating the refinement of existing analytical models.
Materials Science (cond-mat.mtrl-sci)
Scripta Materialia 242 (2024) 115934
Influence of Thermostats on the Dynamics of the Helix-Coil Transition
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-08-22 20:00 EDT
Maximilian Conradi, Henrik Christiansen, Suman Majumder, Fabio Müller, Wolfhard Janke
We present results from all-atom molecular dynamics simulations for the nonequilibrium dynamics of the collapse and helix-coil transition in polyalanine. In particular, we compare the influence of three different thermostats, viz., the Langevin, Andersen, and Nosé-Hoover thermostats. For that purpose, we investigate the nonequilibrium pathways of the transition from the high-temperature random-coil state to the low-temperature helical state. Additionally, we analyze the time evolution of the potential energy and temperature. Our results show only small differences in the observed phenomenology, albeit quantitatively the dynamics appear to be different for the three thermostats.
Soft Condensed Matter (cond-mat.soft)
Nonequilibrium Dynamics of the Helix-Coil Transition in Polyalanine
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-08-22 20:00 EDT
Maximilian Conradi, Henrik Christiansen, Suman Majumder, Fabio Müller, Wolfhard Janke
In this work, the nonequilibrium pathways of the collapse of the helix-forming biopolymer polyalanine are investigated. To this end, the full time evolution of the helix-coil transition is simulated using molecular dynamics simulations. At the start of the transition short $ 3_{10}$ -helices form, seemingly leading to the molecule becoming more aspherical midway through the collapse. After the completed collapse, the formation of $ \alpha$ -helices seems to become the prevalent ordering mechanism leading to helical bundles, a structure representative for the equilibrium behavior of longer chains. The dynamics of this transition is explored in terms of the power-law scaling of two associated relaxation times as a function of the chain length.
Soft Condensed Matter (cond-mat.soft), Chemical Physics (physics.chem-ph)
J. Chem. Phys. 162, 154902 (2025)
Taxonomy of defects in semi-dry transferred CVD graphene
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-08-22 20:00 EDT
Post-transfer in-depth morphological characterization of graphene grown by chemical vapor deposition (CVD) is of great importance to evaluate the quality and to understand the origin of defects of the transferred sheets. Herein, a semi-dry transfer technique is used to peel off millimeter-sized CVD graphene flakes from polycrystalline copper foils and transfer them onto SiO2/Si substrates. We take advantage of the unique feature of this semi-dry process: it preserves the copper substrate, enabling location-specific morphological comparisons between graphene and copper at various stages of the transfer. Thanks to a combination of morphological characterization techniques, this leads to trace and elucidate the origin of various post-transfer graphene defects (cracks, wrinkles, holes, tears). Specifically, thermally induced wrinkles are shown to evolve into nanoscale cracks, while copper surface steps lead to folds. Furthermore, we find that the macroscale topography of the copper foil also plays a critical role in defect formation. This work provides guidelines on how to correctly interpret the post-transfer morphology of graphene films on relevant substrates and how to properly assess their quality. This contributes to the optimization of both the graphene CVD growth and transfer processes for future applications.
Materials Science (cond-mat.mtrl-sci)
21 pages; 11 figures
Multifractality in high-dimensional graphs induced by correlated radial disorder
New Submission | Disordered Systems and Neural Networks (cond-mat.dis-nn) | 2025-08-22 20:00 EDT
We introduce a class of models containing robust and analytically demonstrable multifractality induced by disorder correlations. Specifically, we investigate the statistics of eigenstates of disordered tight-binding models on two classes of rooted, high-dimensional graphs – trees and hypercubes – with a form of strong disorder correlations we term `radial disorder’. In this model, site energies on all sites equidistant from a chosen root are identical, while those at different distances are independent random variables (or their analogue for a deterministic but incommensurate potential, a case of which is also considered). Analytical arguments, supplemented by numerical results, are used to establish that this setting hosts robust and unusual multifractal states. The distribution of multifractality, as encoded in the inverse participation ratios (IPRs), is shown to be exceptionally broad. This leads to a qualitative difference in scaling with system size between the mean and typical IPRs, with the latter the appropriate quantity to characterise the multifractality. The existence of this multifractality is shown to be underpinned by an emergent fragmentation of the graphs into effective one-dimensional chains, which themselves exhibit conventional Anderson localisation. The interplay between the exponential localisation of states on these chains, and the exponential growth of the number of sites with distance from the root, is the origin of the observed multifractality.
Disordered Systems and Neural Networks (cond-mat.dis-nn), Statistical Mechanics (cond-mat.stat-mech), Quantum Physics (quant-ph)
18 pages, 15 figures
Lattice distortions and non-sluggish diffusion in BCC refractory high entropy alloys
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-08-22 20:00 EDT
Jingfeng Zhang, Xiang Xu, Fritz Körmann, Wen Yin, Xi Zhang, Christian Gadelmeier, Uwe Glatzel, Blazej Grabowski, Runxia Li, Gang Liu, Biao Wang, Gerhard Wilde, Sergiy V. Divinski
Refractory high-entropy alloys (RHEAs) have emerged as promising candidates for extreme high-temperature applications, for example, in next-generation turbines and nuclear reactors. In such applications, atomic diffusion critically governs essential properties including creep resistance and microstructural stability. The present study systematically investigates impurity diffusion of Co, Mn, and Zn in single phase (BCC solid solution) HfTiZrNbTa and HfTiZrNbV RHEAs applying the radiotracer technique. A neutron total scattering technique is used to evaluate the pair distribution functions and element-specific lattice distortions in these alloys. \textit{Ab initio}-based calculations give access to lattice distortions and solubilities of the impurities under investigation, including the impact of short-range order. The diffusion results are discussed in relation to calculated substitutional and interstitial solution energies, local lattice distortions, and short-range order effects. Co diffusion is found to be dominated by the interstitial mechanism, exhibiting fast diffusion. These findings reveal important structure-property relationships between local atomic environments and diffusion kinetics in BCC RHEAs, providing critical insights for designing alloys with enhanced high-temperature performance through targeted control of impurity diffusion processes.
Materials Science (cond-mat.mtrl-sci)
18 pages, 8 figures
Acta Materialia 297 (2025) 121283
Reinforcement learning of a biflagellate model microswimmer
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-08-22 20:00 EDT
Many microswimmers are able to swim through viscous fluids by employing periodic non-reciprocal deformations of their appendages. Here we use a simple microswimmer model inspired by swimming biflagellates which consists of a spherical cell body and two small spherical beads representing the motion of the two flagella. Using reinforcement learning we identify for different microswimmer morphologies quasi-optimized swimming strokes. For all studied cases the identified strokes result in symmetric and quasi-synchronized beating of the two flagella beads. Interestingly, the stroke-averaged flow fields are of pusher type, and the observed swimming gaits outperform previously used biflagellate microswimmer models relying on predefined circular flagella bead motion.
Soft Condensed Matter (cond-mat.soft), Biological Physics (physics.bio-ph), Computational Physics (physics.comp-ph)
24 pages, 9 figures
Eur. Phys. J. E 48, 50 (2025)
From Near-Integrable to Far-from-Integrable: A Unified Picture of Thermalization and Heat Transport
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-08-22 20:00 EDT
Weicheng Fu, Zhen Wang, Yisen Wang, Yong Zhang, Hong Zhao
Whether and how a system approaches equilibrium is central in nonequilibrium statistical physics, crucial to understanding thermalization and transport. Bogoliubov’s three-stage (initial, kinetic, and hydrodynamic) evolution hypothesis offers a qualitative framework, but quantitative progress has focused on near-integrable systems like dilute gases. In this work, we investigate the relaxation dynamics of a one-dimensional diatomic hard-point (DHP) gas, presenting a phase diagram that characterizes relaxation behavior across the full parameter space, from near-integrable to far-from-integrable regimes. We analyze thermalization (local energy relaxation in nonequilibrium states) and identify three universal dynamical regimes: (i) In the near-integrable regime, kinetic processes dominate, local energy relaxation decays exponentially, and the thermalization time $ \tau$ scales as $ \tau \propto \delta^{-2}$ . (ii) In the far-from-integrable regime, hydrodynamic effects dominate, energy relaxation decays power-law, and thermalization time scales linearly with system size $ N$ . (iii) In the intermediate regime, the Bogoliubov phase emerges, characterized by the transition from kinetic to hydrodynamic relaxation. The phase diagram also shows that hydrodynamic behavior can emerge in small systems when sufficiently far from the integrable regime, challenging the view that such effects occur only in large systems. In the thermodynamic limit, the system’s relaxation depends on the order in which the limits ($ N \to \infty$ or $ \delta \to 0$ ) are taken. We then analyze heat transport (decay of heat-current fluctuations in equilibrium), demonstrating its consistency with thermalization, leading to a unified theoretical description of thermalization and transport. Our approach provides a pathway for studying relaxation dynamics in many-body systems, including quantum systems.
Statistical Mechanics (cond-mat.stat-mech)
14 pages, 7 figures
Controlling polymerization-induced phase separation in the synthesis of porous gels
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-08-22 20:00 EDT
Yanxia Feng, Noel Ringeisen, Eric R. Dufresne, Lucio Isa, Robert W. Style
Porous gels – gels with solvent-filled pores that are much larger than their mesh size – are widely used in engineering and biomedical applications due to their tunable mechanics, high water content, and selective permeability. Among various strategies to create porous gels, polymerization-induced phase separation (PIPS) has shown particular promise. However, the conditions that trigger and control PIPS remain poorly understood. Here, we systematically investigate the influence of solvent quality, polymeric precursor molecular weight, and polymer concentration on phase separation in polymerizing poly(ethylene glycol) diacrylate gels. We find that phase separation occurs when the precursor solution concentration is below the overlap concentration. Phase-separated gels have a pore geometry that is controlled by solvent quality: better solvents result in smaller pores, while worse solvents can create superporous, highly-absorbant gels. Motivated by our results, we propose a theory that predicts when phase separation occurs in polymerizing gels, applicable across a wide range of polymer/solvent gel systems. Our results provide a framework for the rational design of porous gels.
Soft Condensed Matter (cond-mat.soft), Materials Science (cond-mat.mtrl-sci)
6 figures
Automated Modeling of Polarons: Defects and Reactivity on TiO$_2$(110) Surfaces
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-08-22 20:00 EDT
Firat Yalcin, Carla Verdi, Viktor C. Birschitzky, Matthias Meier, Michael Wolloch, Michele Reticcioli
Polarons are widespread in functional materials and are key to device performance in several technological applications. However, their effective impact on material behavior remains elusive, as condensed matter studies struggle to capture their intricate interplay with atomic defects in the crystal. In this work, we present an automated workflow for modeling polarons within density functional theory (DFT). Our approach enables a fully automatic identification of the most favorable polaronic configurations in the system. Machine learning techniques accelerate predictions, allowing for an efficient exploration of the defect-polaron configuration space. We apply this methodology to Nb-doped TiO$ _2$ (110) surfaces, providing new insights into the role of defects in surface reactivity. Using CO adsorbates as a probe, we find that Nb doping has minimal impact on reactivity, whereas oxygen vacancies contribute significantly depending on their local arrangement via the stabilization of polarons on the surface atomic layer. Our package streamlines the modeling of charge trapping and polaron localization with high efficiency, enabling systematic, large-scale investigations of polaronic effects across complex material systems.
Materials Science (cond-mat.mtrl-sci)
14 pages, 6 figures
Optimizing energy conversion with nonthermal resources in steady-state quantum devices
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-08-22 20:00 EDT
Elsa Danielsson, Henning Kirchberg, Janine Splettstoesser
We provide a framework for optimizing energy conversion processes in coherent quantum conductors fed by nonthermal resources. Such nonthermal resources, which cannot be characterized by temperatures or electrochemical potentials, occur in small-scale systems that are smaller than their thermalization length. Using scattering theory in combination with a Lagrange multiplier method, we optimize the device’s performance based on the efficiency, precision, or a trade-off between the two at a given output current. The transmission properties leading to this optimal performance are identified. We showcase our findings with the example of a refrigerator exploiting experimentally relevant nonthermal resources, which could result from competing environments or from light irradiation. We show that the performance is improved compared to a device exploiting a thermal resource. Our results can serve as guidelines for the design of energy-conversion processes in future nanoelectronic devices.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Quantum Physics (quant-ph)
Experimental determination and micromagnetic analysis of spin wave modes in cylindrical nanowires
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-08-22 20:00 EDT
Niklas Martin, Laura Álvaro-Gómez, Lucas Perez, André Thiaville, Jean-Paul Adam, Olivier Fruchart, Aurélien Masseboeuf
We report an experimental study of spin wave modes in individual cylindrical nanowires, a textbook situation of confined spin waves in 3D nanomagnetism. We observe discrete modes of thermal spin waves with micro-Brillouin light scattering, whose frequencies $ f$ shift to higher values as the applied longitudinal induction magnetic field $ B_z$ increases. Micromagnetic simulations allowed us to associate every $ f(B_z)$ curve to a given spatial mode, labeled with radial and azimuthal indices $ \ell$ and $ m$ .
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
8 pages, 7 figures
Predictive models for strain energy in condensed phase reactions
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-08-22 20:00 EDT
Baptiste Martin, Shukai Yao, Chunyu Li, Anthony Bocahut, Matthew Jackson, Alejandro Strachan
Molecular modeling of thermally activated chemistry in condensed phases is essential to understand polymerization, depolymerization, and other processing steps of molecular materials. Current methods typically combine molecular dynamics (MD) simulations to describe short-time relaxation with a stochastic description of predetermined chemical reactions. Possible reactions are often selected on the basis of geometric criteria, such as a capture distance between reactive atoms. Although these simulations have provided valuable insight, the approximations used to determine possible reactions often lead to significant molecular strain and unrealistic structures. We show that the local molecular environment surrounding the reactive site plays a crucial role in determining the resulting molecular strain energy and, in turn, the associated reaction rates. We develop a graph neural network capable of predicting the strain energy associated with a cyclization reaction from the pre-reaction, local, molecular environment surrounding the reactive site. The model is trained on a large dataset of condensed-phase reactions during the activation of polyacrylonitrile (PAN) obtained from MD simulations and can be used to adjust relative reaction rates in condensed systems and advance our understanding of thermally activated chemical processes in complex materials
Materials Science (cond-mat.mtrl-sci)
Ultrastrong and ductile CoNiMoAl medium-entropy alloys enabled by L12 nanoprecipitate-induced multiple deformation mechanisms
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-08-22 20:00 EDT
Min Young Sung, Tae Jin Jang, Sang Yoon Song, Gunjick Lee, KenHee Ryou, Sang-Ho Oh, Byeong-Joo Lee, Pyuck-Pa Choi, Jörg Neugebauer, Blazej Grabowski, Fritz Körmann, Yuji Ikeda, Alireza Zargaran, Seok Su Sohn
L12 precipitates are known to significantly enhance the strength and ductility of single-phase face-centered cubic (FCC) medium- or high-entropy alloys (M/HEAs). However, further improvements in mechanical properties remain untapped, as alloy design has historically focused on systems with specific CrCoNi- or FeCoCrNi-based FCC matrix and Ni3Al L12 phase compositions. This study introduces novel Co-Ni-Mo-Al alloys with L12 precipitates by systematically altering Al content, aiming to bridge this research gap by revealing the strengthening mechanisms. The (CoNi)81Mo12Al7 alloy achieves yield strength of 1086 MPa, tensile strength of 1520 MPa, and ductility of 35 %, demonstrating an impressive synergy of strength, ductility, and strain-hardening capacity. Dislocation analysis via transmission electron microscopy, supported by generalized stacking fault energy (GSFE) calculations using density functional theory (DFT), demonstrates that Mo substitution for Al in the L12 phase alters dislocation behavior, promoting the formation of multiple deformation modes, including stacking faults, super-dislocation pairs, Lomer-Cottrell locks, and unusual nano-twin formation even at low strains. These behaviors are facilitated by the low stacking fault energy (SFE) of the FCC matrix, overlapping of SFs, and dislocation dissociation across anti-phase boundaries (APBs). The increased energy barrier for superlattice intrinsic stacking fault (SISF) formation compared to APBs, due to Mo substitution, further influences dislocation activity. This work demonstrates a novel strategy for designing high-performance M/HEAs by expanding the range of FCC matrix and L12 compositions through precipitation hardening.
Materials Science (cond-mat.mtrl-sci)
J. Mater. Sci. Technol. 225, 72 (2025)
Electronic structure of the interface between Au and WSe2
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-08-22 20:00 EDT
Laxman Nagireddy, Samuel J. Magorrian, Matthew D. Watson, Yogal Prasad Ghimirey, Marc Walker, Cephise Cacho, Neil R. Wilson, Nicholas D. M. Hine
Understanding the interface between metals and two-dimensional materials is critical for their application in electronics and for the development of metal-mediated exfoliation of large area monolayers. Studying the intricate interactions at the interface requires model systems that enable control of the roughness, purity, and crystallinity of the metal surface. Here, we investigate the layer-dependent electronic structure of WSe_2 on template-stripped gold substrates fabricated using both silicon and mica templates, giving crystallographically disordered and Au(111) ordered surfaces, respectively, and contrast these findings with ab initio predictions. We observe strong hybridization around the Brillouin zone centre at $ \overline{\Gamma}$ , indicating a covalent admixture in the gold-\WSe~interaction, and band shifts that suggest charge rearrangement at the Au(111) / WSe_2 interface. Core-level spectroscopy shows a single chemical environment for the interfacial WSe_2 layer on the template-stripped gold, distinct from the subsequent layers. These results reveal a mixture of van der Waals and covalent interactions, best described as a covalent-like quasi-bonding with intermediate interaction strength.
Materials Science (cond-mat.mtrl-sci)
Superpotentials, flat bands and the role of Quantum Geometry for the superfluid stiffness
New Submission | Superconductivity (cond-mat.supr-con) | 2025-08-22 20:00 EDT
T. Bauch, F. Lombardi, G. Seibold
We investigate the stability and enhancement of superconductivity in a system subject to a 2D periodic superpotential. This externally imposed modulation leads to a reconstructed multi-band structure with flat bands emerging in certain energy regions. When the chemical potential is tuned into one of these flat bands, the associated increase in the density of states can strongly enhance the superconducting critical temperature Tc compared to the homogeneous case while maintaining the superfluid stiffness Ds at a sizeable value. We also clarify the role of the quantum geometric effect for flat bands in such topologically trivial systems. While the overall paramagnetic interband contribution to the stiffness is negative we identify a class of certain interband scattering processes which enhance Ds and scale with the interaction, playing therefore the same role as quantum geometric effects in conventional flat band models. The enhancement of superconductivity is found to be robust against weak to moderate disorder, suggesting that the system is not overly sensitive to imperfections which is an important prerequisite for experimental realizations. Our results demonstrate that engineered superpotentials offer a compelling alternative to twist-based moire systems, providing a pathway toward tailoring superconductivity via lithographic design.
Superconductivity (cond-mat.supr-con)
11 pages, 10 figures
Octahedral tilting and B-site off-centering in halide perovskites are not coupled
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-08-22 20:00 EDT
Colin M. Hylton-Farrington, Richard C. Remsing
Metal halide perovskites show exceptional potential for solar energy, thermoelectrics, catalysis, and other photochemical technologies, with performance rooted in electronic structure-driven properties. In ABX3 halide perovskites, localized and often aspherical local electron densities from B-site lone pairs or polarizable X- anions can distort the lattice. However, the links among electronic structure fluctuations and distortions like tilting of the BX6 octahedra and off-centering of the B-site from the center of its octahedron are not fully understood. Using group theory and ab initio molecular dynamics, we quantify how lone pairs, halide polarization, off-centering, and octahedral tilting interact in the cubic phase CsBBr3, with B = Pb, Sn, and Ge. We find that lone pair-induced off-centering and octahedral tilting are symmetry-decoupled. Instead, stereochemical lone pair expression of the B-site ion is correlated to octahedral tilting through the propensity of the B-site to form a transient, partial covalent bond with the surrounding halide ions that stiffens octahedral tilting modes. These results link local electronic asymmetry to structural fluctuations and suggest that dynamic modulation of electronic symmetry offers a pathway to control functional properties in halide perovskites.
Materials Science (cond-mat.mtrl-sci), Chemical Physics (physics.chem-ph)
10 pages, 6 figures
Universal Machine Learning Potential for Systems with Reduced Dimensionality
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-08-22 20:00 EDT
Giulio Benedini, Antoine Loew, Matti Hellstrom, Silvana Botti, Miguel A. L. Marques
We present a benchmark designed to evaluate the predictive capabilities of universal machine learning interatomic potentials across systems of varying dimensionality. Specifically, our benchmark tests zero- (molecules, atomic clusters, etc.), one- (nanowires, nanoribbons, nanotubes, etc.), two- (atomic layers and slabs) and three-dimensional (bulk materials) compounds. The benchmark reveals that while all tested models demonstrate excellent performance for three-dimensional systems, accuracy degrades progressively for lower-dimensional structures. The best performing models for geometry optimization are orbital version 2, equiformerV2, and the equivariant Smooth Energy Network, with the equivariant Smooth Energy Network also providing the most accurate energies. Our results indicate that the best models yield, on average, errors in the atomic positions in the range of 0.01-0.02 angstrom and errors in the energy below 10~meV/atom across all dimensionalities. These results demonstrate that state-of-the-art universal machine learning interatomic potentials have reached sufficient accuracy to serve as direct replacements for density functional theory calculations, at a small fraction of the computational cost, in simulations spanning the full range from isolated atoms to bulk solids. More significantly, the best performing models already enable efficient simulations of complex systems containing subsystems of mixed dimensionality, opening new possibilities for modeling realistic materials and interfaces.
Materials Science (cond-mat.mtrl-sci), Computational Physics (physics.comp-ph)
Shear induced topological changes of local structure in dense colloidal suspensions
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-08-22 20:00 EDT
Ratimanasee Sahu, Abhishek Kumar Gupta, Peter Schall, Sarika Maitra Bhattacharyya, Vijayakumar Chikkadi
Understanding the structural origins of glass formation and mechanical response remains a central challenge in condensed matter physics. Recent studies have identified the local caging potential experienced by a particle due to its nearest neighbors as a robust structural metric that links microscopic structure to dynamics under thermal fluctuations and applied shear. However, its connection to locally favored structural motifs has remained unclear. Here, we analyze structural motifs in colloidal crystals and glasses and correlate them with the local caging potential. We find that icosahedral motifs in glasses are associated with deeper caging potentials than crystalline motifs such as face-centered cubic (FCC) and hexagonal close-packed (HCP) structures. Both crystalline and amorphous systems also contain large number of particles belonging to stable defective motifs, which are distortions of the regular motifs. Under shear, large clusters of defective motifs fragment into smaller ones, driving plastic deformation and the transition from a solid-like to a liquid-like state in amorphous suspensions. Particles that leave clusters of stable motifs are associated with shallower caging potentials and are more prone to plastic rearrangements, ultimately leading to motif disintegration during shear. Our results thus reveal that the loss of mechanical stability in amorphous suspensions is governed by the topological evolution of polytetrahedral motifs, uncovering a structural mechanism underlying plastic deformation and fluidization.
Soft Condensed Matter (cond-mat.soft)
Direct energy dissipation measurements for a driven superfluid via the harmonic-potential theorem
New Submission | Quantum Gases (cond-mat.quant-gas) | 2025-08-22 20:00 EDT
Clara Tanghe, Senne Van Wellen, Kobe Vergaerde, Karel Van Acoleyen
We propose and experimentally demonstrate a method to directly measure energy dissipation for a linearly driven superfluid confined in a harmonic trap. The method relies on a perturbed version of the harmonic-potential theorem, according to which a potential perturbation - effectively acting as a stirrer - converts center-of-mass motional energy into internal energy. Energy conservation then enables a direct, quantitative determination of the dissipated energy from measurements of the macroscopic center-of-mass observables. Applying this method to a perturbed, driven Bose-Einstein condensate, we observe dissipation curves characteristic of superfluid flow, including a critical velocity that depends on the stirrer strength, consistent with previous studies. Our results are supported by mean-field simulations, which corroborate both the theoretical framework and the experimental findings.
Quantum Gases (cond-mat.quant-gas), Quantum Physics (quant-ph)
13 pages, 10 figures
High Harmonic Spectroscopy from Lower-Order to Higher-Order Topological Insulators
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-08-22 20:00 EDT
Bryan Lorenzo, Camilo Granados, Dasol Kim, Carlos Batista, Jean Menotti, Feng Liu, Wenlong Gao, Alexis Chacon
Over the last decade, high-harmonic spectroscopy has been successfully extended to the study of ultrafast electron motion in solids, shedding light on fundamental processes such as Bloch oscillations and higher-order nonlinear phenomena. In this work, we present theoretical studies of high-harmonic spectroscopy applied to topological materials including higher-order ones, focusing on several key observables associated with high-harmonic generation - namely, helicity, circular dichroism, and ellipticity dependence. We extend current all-optical measurement approaches from lower-order topological insulators (LOTIs) to higher-order topological insulators (HOTIs), employing three distinct models: a Haldane model for Chern insulators, Kane-Mele model for topological insulators, and a breathing Kagome lattice for HOTIs. This work aims to resolve whether helicity, circular dichroism, and ellipticity dependence can reveal signatures of topological states. For the Chern insulators and topological insulators, we find that these observables can indeed capture topological phases. In contrast, for HOTIs, no clear signatures of topology emerge in the harmonic spectrum, suggesting that a more careful analysis is required to identify topological invariants in higher-order topological insulators. In particular, for the topological semimetal phase, we find a harmonic enhancement by two to three orders of magnitude in the Kagome lattice. Our study delineates the conditions under which high-harmonic spectroscopy serves as a unique tool for diagnosing topological phases, particularly for those associated with topological corner states.
Materials Science (cond-mat.mtrl-sci)
Second Harmonic Generation by Multilayer Graphenes and its Dependence on Stacking Order and Encapsulation Environment
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-08-22 20:00 EDT
Patrick Johansen Sarsfield, Takaaki V. Joya, Takuto Kawakami, Mikito Koshino, Vladimir Fal’ko
In this work, we analyze the effects of external influences on the second harmonic generation (SHG) signal produced by multilayer graphenes. Specifically, we vary the encapsulation conditions and doping of graphenes, seeking to identify SHG “fingerprints” that are unsensitive to external perturbations. We identify characteristic features in the infrared regime that may be used as a stacking-order fingerprint for the mixed stacking tetralayer and the trilayer polytypes caused by a strong double resonance effect. Further to this, we find that the tetralayers systematically produce an SHG response that is significantly larger as compared to the trilayers. We then studied the SHG signal by the tetralayer polytypes in the terahertz regime and demonstrated the signal is highly sensitive the environmental conditions. Furthermore, we also find that accidental doping of graphene will strongly suppress the SHG signal in this regime. The above findings emphasize the need for a spectral approach to the identification of stacking order by SHG. Thus, measurements at one frequency are insufficient to confidently identify the stacking order due to the environmental sensitivities, since SHG can be readily induced with a comparable magnitude in the centrosymmetric polytypes through external symmetry-breaking.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
8 pages, 4 figures
Classification of Magnetism and Altermagnetism in Quasicrystals
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-08-22 20:00 EDT
Zhi-Yan Shao, Chen Lu, Zhiming Pan, Yu-Bo Liu, Fan Yang
Altermagnetism, an unconventional magnetic phase characterized by zero net magnetism and a spin-split electronic band, has been studied exclusively in conventional crystalline materials. In this work, we extend the theoretical framework of altermagnetism to quasicrystals (QCs), which lack translational symmetry. We classify magnetic phases in 2D QCs with $ n$ -fold rotational symmetry without spin-orbit coupling, by using the irreducible representation (IRRP) of the $ D_n$ point group. Based on symmetry analysis, we propose the conjecture that magnetic phases corresponding to 1D non-identity IRRPs are generally altermagnetic, with the exception of those possessing parity-time symmetry. To verify our conjecture, we take the Hubbard model as an example and develop a systematic approach to determine the magnetic pattern in the QC, which effectively avoids getting trapped at local energy minima. Consequently, our tests for the Hubbard model on various QCs with different symmetries are unexceptionally consistent with our proposal. Our work highlights the QC as a platform where the altermagnetism is common among magnetic phases.
Strongly Correlated Electrons (cond-mat.str-el)
4.2pages, with Appendix
End-to-End Analysis of Charge Stability Diagrams with Transformers
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-08-22 20:00 EDT
Rahul Marchand, Lucas Schorling, Cornelius Carlsson, Jonas Schuff, Barnaby van Straaten, Taylor L. Patti, Federico Fedele, Joshua Ziegler, Parth Girdhar, Pranav Vaidhyanathan, Natalia Ares
Transformer models and end-to-end learning frameworks are rapidly revolutionizing the field of artificial intelligence. In this work, we apply object detection transformers to analyze charge stability diagrams in semiconductor quantum dot arrays, a key task for achieving scalability with spin-based quantum computing. Specifically, our model identifies triple points and their connectivity, which is crucial for virtual gate calibration, charge state initialization, drift correction, and pulse sequencing. We show that it surpasses convolutional neural networks in performance on three different spin qubit architectures, all without the need for retraining. In contrast to existing approaches, our method significantly reduces complexity and runtime, while enhancing generalizability. The results highlight the potential of transformer-based end-to-end learning frameworks as a foundation for a scalable, device- and architecture-agnostic tool for control and tuning of quantum dot devices.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Materials Science (cond-mat.mtrl-sci), Machine Learning (cs.LG), Quantum Physics (quant-ph)
8 pages, 2 figures, RM and LS contributed equally
Orientation dependent anomalous Hall and spin Hall currents at the junctions of altermagnets with $p$-wave magnets
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-08-22 20:00 EDT
Sachchidanand Das, Abhiram Soori
We study charge and spin transport across a junction between an altermagnet (AM) and a $ p$ -wave magnet (PM) using a continuum model with boundary conditions tailored to the spin-split band structures of the two materials. Remarkably, although neither AM nor PM is spin-polarized, we find that the junction supports finite spin currents both longitudinally and transversely. We compute the longitudinal and transverse charge and spin conductivities as functions of the crystallographic orientations and the relative angle between the Néel vectors of AM and PM. Our results reveal that transverse charge and spin conductivities can be finite even when the longitudinal charge conductivity vanishes. For suitable parameter choices and orientation angles, the transverse conductivities are more prominent than the longitudinal ones. The origin of these effects lies in the matching and mismatching of transverse momentum modes ($ k_y$ ) across the junction combined with the spin-dependent band splitting in AM and PM. Furthermore, while the transverse charge conductivity may cancel for certain orientations, the transverse spin conductivity remains finite due to unequal contributions of opposite $ k_y$ channels. These findings highlight altermagnet/$ p$ -wave magnet junctions as a promising platform for tunable generation and control of transverse charge and spin currents driven purely by crystallographic orientation and spin structure.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Materials Science (cond-mat.mtrl-sci)
7 pages, 6 captioned figures. Comments are welcome
Exploring the Landscape of Non-Equilibrium Memories with Neural Cellular Automata
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-08-22 20:00 EDT
Ethan Lake, Ehsan Pajouheshgar
We investigate the landscape of many-body memories: families of local non-equilibrium dynamics that retain information about their initial conditions for thermodynamically long time scales, even in the presence of arbitrary perturbations. In two dimensions, the only well-studied memory is Toom’s rule. Using a combination of rigorous proofs and machine learning methods, we show that the landscape of 2D memories is in fact quite vast. We discover memories that correct errors in ways qualitatively distinct from Toom’s rule, have ordered phases stabilized by fluctuations, and preserve information only in the presence of noise. Taken together, our results show that physical systems can perform robust information storage in many distinct ways, and demonstrate that the physics of many-body memories is richer than previously realized. Interactive visualizations of the dynamics studied in this work are available at this https URL.
Statistical Mechanics (cond-mat.stat-mech), Computer Vision and Pattern Recognition (cs.CV), Machine Learning (cs.LG), Cellular Automata and Lattice Gases (nlin.CG)
4+9 pages
Regularized Perturbation Theory for Ab initio Solids
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-08-22 20:00 EDT
Meng-Fu Chen, Jinghong Zhang, Hieu Q. Dinh, Adam Rettig, Joonho Lee
Second-order Moller-Plesset perturbation theory (MP2) for ab initio simulations of solids is often limited by divergence or over-correlation issues, particularly in metallic, narrow-gap, and dispersion-stabilized systems. We develop and assess three regularized second-order perturbation theories: $ \kappa$ -MP2, $ \sigma$ -MP2, and the size-consistent Brillouin-Wigner approach (BW-s2), across metals, semiconductors, molecular crystals, and rare gas solids. BW-s2 achieves high accuracy for cohesive energies, lattice constants, and bulk moduli in metals, semiconductors, and molecular crystals, rivaling or surpassing coupled-cluster with singles and doubles at lower cost. In rare gas solids, where MP2 already underbinds, $ \kappa$ -MP2 does not make the results much worse while BW-s2 struggles. These results illustrate both the potential and the limitations of regularized perturbation theory for efficient and accurate solid-state simulations. While broader testing is warranted, BW-s2($ \alpha$ = 2) appears particularly promising, with possible advantages over modern random-phase approximations and coupled-cluster theory.
Materials Science (cond-mat.mtrl-sci), Chemical Physics (physics.chem-ph), Computational Physics (physics.comp-ph)
PyKirigami: An interactive Python simulator for kirigami metamaterials
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-08-22 20:00 EDT
Qinghai Jiang, Gary P. T. Choi
In recent years, the concept of kirigami has been used in creating deployable structures for various scientific and technological applications. While the design of kirigami metamaterials has been widely studied, the simulation of the deployment and shape transformation process is less explored. In this work, we develop PyKirigami, an efficient Python-based open-source computational tool for the deployment simulation of kirigami metamaterials. In particular, our tool is capable of simulating both two- and three-dimensional deployments of a large variety of kirigami metamaterials with different geometric, topological, and physical properties. Altogether, our work paves a new way for the modelling and design of shape-morphing mechanical metamaterials.
Soft Condensed Matter (cond-mat.soft), Materials Science (cond-mat.mtrl-sci), Computational Geometry (cs.CG)
Skyrmion Lattice Order Controlled by Confinement Geometry
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-08-22 20:00 EDT
Raphael Gruber, Jan Rothörl, Simon M. Fröhlich, Maarten A. Brems, Fabian Kammerbauer, Maria-Andromachi Syskaki, Elizabeth M. Jefremovas, Sachin Krishnia, Asle Sudbø, Peter Virnau, Mathias Kläui
Magnetic skyrmions forming two-dimensional (2D) lattices provide a versatile platform for investigating phase transitions predicted by Kosterlitz-Thouless-Halperin-Nelson-Young (KTHNY) theory. While 2D melting in skyrmion systems has been demonstrated, achieving controlled ordering in skyrmion lattices remains challenging due to pinning effects from a non-uniform energy landscape, which often results in polycrystalline structures. Skyrmions in thin films, however, offer thermal diffusion with high tunability and can be directly imaged via Kerr microscopy, enabling real-time observation of their dynamics. To regulate lattice order in such flexible systems, we introduce geometric confinements of varying shapes. Combining Kerr microscopy experiments with Thiele model simulations, we demonstrate that confinement geometry critically influences lattice order. Specifically, hexagonal confinements commensurate with the skyrmion lattice stabilize monodomain hexagonal ordering, while incommensurate geometries induce domain formation and reduce overall order. Understanding these boundary-driven effects is essential for advancing the study of 2D phase behavior and for the design of skyrmion-based spintronic applications, ranging from memory devices to unconventional computing architectures.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Materials Science (cond-mat.mtrl-sci), Statistical Mechanics (cond-mat.stat-mech)