CMP Journal 2025-03-31
Statistics
Nature Materials: 1
Nature Nanotechnology: 2
Nature Physics: 6
arXiv: 66
Nature Materials
Water uptake of solids and its impact on ion transport
Review Paper | Electrochemistry | 2025-03-30 20:00 EDT
Markus Joos, Xiaolan Kang, Rotraut Merkle, Joachim Maier
The interaction modes of water with (polar) solids are manifold, comprising surface adsorption and incorporation into the bulk, both in molecular and in dissociated form. This Review discusses these processes and the respective pronounced effects on the ionic transport properties. The concentration as well as the mobility of ionic carriers can vary by orders of magnitude depending on the water content on or within a solid. Selected materials examples, which are relevant for electrochemical devices (for example, low- and intermediate-temperature fuel cells) or which are of fundamental interest (such as molecular water acting as dopant in a lithium halide), are treated in more detail. Interrelations between hydration and electronic defects are also briefly touched upon.
Electrochemistry, Fuel cells
Nature Nanotechnology
Enhanced Majorana stability in a three-site Kitaev chain
Original Paper | Quantum information | 2025-03-30 20:00 EDT
Alberto Bordin, Chun-Xiao Liu, Tom Dvir, Francesco Zatelli, Sebastiaan L. D. ten Haaf, David van Driel, Guanzhong Wang, Nick van Loo, Yining Zhang, Jan Cornelis Wolff, Thomas Van Caekenberghe, Ghada Badawy, Sasa Gazibegovic, Erik P. A. M. Bakkers, Michael Wimmer, Leo P. Kouwenhoven, Grzegorz P. Mazur
Majorana zero modes are non-Abelian quasiparticles predicted to emerge at the edges of topological superconductors. A one-dimensional topological superconductor can be realized with the Kitaev model–a chain of spinless fermions coupled via p-wave superconductivity and electron hopping–which becomes topological in the long-chain limit. Here we realize a three-site Kitaev chain using semiconducting quantum dots coupled by superconducting segments in a hybrid InSb/Al nanowire. We investigate the robustness of Majorana zero modes under varying coupling strengths and electrochemical potentials, comparing two- and three-site chains realized within the same device. We observe that extending the chain to three sites enhances the stability of the zero-energy modes, especially against variations in the coupling strengths. This experiment lacks superconducting phase control, yet numerical conductance simulations with phase averaging align well with our observations. Our results demonstrate the scalability of quantum-dot-based Kitaev chains and its benefits for Majorana stability.
Quantum information, Superconducting devices, Superconducting properties and materials
Asymmetric photooxidation of glycerol to hydroxypyruvic acid over Rb-Ir catalytic pairs on poly(heptazine imides)
Original Paper | Photocatalysis | 2025-03-30 20:00 EDT
Zhenyuan Teng, Zhenzong Zhang, Ying Tu, Qitao Zhang, Nan Jian, Liujun Yang, Jiadong Xiao, Jie Ding, Longzhen Huang, Ohno Teruhsia, Chengyin Wang, Dengsong Zhang, Han Yu, Jianmei Lu, Chenliang Su, Bin Liu
Selective asymmetric oxidation of glycerol (GLY) to hydroxypyruvic acid (HPA) offers an attractive approach for chiral drug synthesis, but this process is highly challenging. Here we develop a photocatalytic method to achieve heterogeneous selective photooxidation of GLY to HPA over rubidium (Rb) and iridium (Ir) catalytic pairs decorated on a poly(heptazine imide) framework. The Rb sites effectively adsorb GLY molecules through the terminal -OH groups, thus inhibiting their oxidation during photoreaction, while the Ir sites enhance the oxygen reduction reaction and the in situ generated surficial oxygen-reduction radicals on Ir can protect the reactive C-centred radical intermediates produced during photooxidation. The spatial arrangement of Rb and Ir sites facilitates hydrogen extraction–an essential rate-determining step for GLY photooxidation–and protects C3 radical intermediates from overoxidation. This photocatalytic system achieves a remarkable productivity for HPA synthesis (~8,000 μmol of HPA per gram of photocatalyst per hour) under visible-light illumination.
Photocatalysis
Nature Physics
Yielding behaviour of active particles in bulk and in confinement
Original Paper | Biological physics | 2025-03-30 20:00 EDT
Yagyik Goswami, G. V. Shivashankar, Srikanth Sastry
Collective behaviour in dense assemblies of self-propelled active particles occurs in a wide range of biological phenomena, including the dynamical transitions of cellular and subcellular biological assemblies such as the cytoskeleton and the cell nucleus. Here, motivated by observations of mechanically induced changes in the dynamics of such systems and the apparent role of confinement geometry, we show that the fluidization transition broadly resembles yielding in amorphous solids, which is consistent with recent suggestions. More specifically, however, we find that a detailed analogy holds with the yielding transition under cyclic shear deformation, for large but finite persistence times. The fluidization transition is accompanied by driving-induced annealing, strong dependence on the initial state of the system, a divergence of timescales to reach steady states and a discontinuous onset of diffusive motion. We also observe a striking dependence of transition on persistence times and on the nature of confinement. Collectively, our results have implications for biological assemblies in confined geometries, including epigenetic cell-state transitions.
Biological physics, Statistical physics
Cooperative hydrodynamics accompany multicellular-like colonial organization in the unicellular ciliate Stentor
Original Paper | Biological physics | 2025-03-30 20:00 EDT
Shashank Shekhar, Hanliang Guo, Sean P. Colin, Wallace Marshall, Eva Kanso, John H. Costello
Many single-celled organisms exhibit both solitary and colonial existence. An important step towards multicellularity, which is associated with benefits such as enhanced nutrient uptake, was the formation of colonies of unicellular organisms. However, the initial drivers that favoured individual cells aggregating into more complex colonies are less clear. Here we show that hydrodynamic coupling between proximate neighbours results in faster feeding flows for neighbouring ciliates, such that individuals within a dynamic colony have stronger average feeding flows than solitary individuals. Flows generated by individuals acting together reach higher velocities, thus allowing access to a wider range of prey resources than individuals acting on their own. Moreover, we find that accrued feeding benefits are typically asymmetric: whereas all individuals benefit from acting together, those with slower solitary currents gain more from partnering than those with faster currents. We find that colonial organization in simple unicellular organisms is beneficial for all its members. This provides fundamental insights into the selective forces favouring the early evolution of multicellular organization.
Biological physics, Fluid dynamics, Microbiology
Thermopower probes of emergent local moments in magic-angle twisted bilayer graphene
Original Paper | Electronic properties and devices | 2025-03-30 20:00 EDT
Ayan Ghosh, Souvik Chakraborty, Ranit Dutta, Adhip Agarwala, K. Watanabe, T. Taniguchi, Sumilan Banerjee, Nandini Trivedi, Subroto Mukerjee, Anindya Das
Recent experiments on magic-angle twisted bilayer graphene have shown the formation of flat bands, suggesting that electronic correlation effects are likely to dominate in this material. However, a global transport measurement showing distinct signatures of strong correlations–such as local moments arising from the flat bands–is missing. Here we demonstrate the presence of emergent local moments through their impact on entropy extracted from thermopower measurements. In addition to sign changes in the thermopower at the Dirac point and full filling of the flat bands, we observe sign changes near the quarter-filled bands that do not vary with temperature from 5 K to 60 K. This is in contrast to temperature-dependent crossing points seen in our study on twisted bilayer graphene devices with weaker correlations. Furthermore, we find that applying a magnetic field reduces the thermopower, consistent with spin entropy suppression observed in layered oxides under partial spin polarization. Neither the robust crossing points nor the suppression by a magnetic field can be explained solely from the contributions of band fermions; instead, our data suggest a dominant contribution coming from the entropy of the emergent localized moments of a strongly correlated flat band.
Electronic properties and devices, Electronic properties and materials
Direct observation of colloidal quasicrystallization
Original Paper | Colloids | 2025-03-30 20:00 EDT
Yan Gao, Brennan Sprinkle, David W. M. Marr, Ning Wu
Discovered first in synthetic alloys and subsequently in nature, quasicrystals exhibit forbidden symmetries and long-range orientational order but lack translational periodicity. Despite numerous theoretical and numerical studies, the fabrication of quasicrystals remains a challenge, with limited means available for observing their formation in situ. As a result, questions remain regarding the detailed mechanisms of quasicrystal formation and stabilization. Observable under optical microscopes, micrometre-scale colloidal systems have been used for decades as atomic models with considerably slowed-down dynamics and tuneable interactions through surface modification, solution composition and applied external fields. Here we show that two-dimensional dodecagonal quasicrystals can be reversibly assembled from single-component microspheres using a combination of orthogonally applied magnetic and electric fields. Varying the magnitude and frequency of the applied fields not only determines the resulting structures but also sets the phase transition dynamics via an effective system temperature. We hypothesize that these quasicrystals are energetically stabilized with their formation driven by an isotropic double-well pair potential, although the origin of the second minimum remains an open question.
Colloids, Self-assembly
Circadian coupling orchestrates cell growth
Original Paper | Biological physics | 2025-03-30 20:00 EDT
Nica Gutu, Malthe S. Nordentoft, Marlena Kuhn, Carolin Ector, Marie Möser, Anna-Marie Finger, Mathias Spliid Heltberg, Mogens Høgh Jensen, Ulrich Keilholz, Achim Kramer, Hanspeter Herzel, Adrián E. Granada
Single-cell circadian oscillators exchange extracellular information to sustain coherent circadian rhythms at the tissue level. The circadian clock and the cell cycle couple within cells but the mechanisms underlying this interplay are poorly understood. We show that the loss of extracellular circadian synchronization disrupts circadian and cell cycle coordination within individual cells, impeding collective tissue growth. We use the theory of coupled oscillators combined with live population, and single-cell recordings and precise experimental perturbations. Coherent circadian rhythms yield oscillatory growth patterns, which unveil a global timing regulator of tissue dynamics. Knocking out core circadian elements abolishes the observed effects, highlighting the central role of circadian clock regulation. Our results underscore the role of tissue-level circadian disruption in regulating proliferation, thereby linking disrupted circadian clocks with oncogenic processes. These findings illuminate the intricate interplay between circadian rhythms, cellular signalling and tissue physiology and enhance our understanding of tissue homeostasis and growth regulation in the context of both health and disease.
Biological physics, Computational biophysics
Crystal-symmetry-paired spin-valley locking in a layered room-temperature metallic altermagnet candidate
Original Paper | Magnetic properties and materials | 2025-03-30 20:00 EDT
Fayuan Zhang, Xingkai Cheng, Zhouyi Yin, Changchao Liu, Liwei Deng, Yuxi Qiao, Zheng Shi, Shuxuan Zhang, Junhao Lin, Zhengtai Liu, Mao Ye, Yaobo Huang, Xiangyu Meng, Cheng Zhang, Taichi Okuda, Kenya Shimada, Shengtao Cui, Yue Zhao, Guang-Han Cao, Shan Qiao, Junwei Liu, Chaoyu Chen
Previous theoretical efforts have predicted a type of unconventional antiferromagnet characterized by a crystal symmetry that connects antiferromagnetic sublattices in real space and simultaneously couples spin and momentum in reciprocal space. This results in a unique crystal-symmetry-paired spin-valley locking and related properties including piezomagnetism and non-collinear spin current even without spin-orbit coupling. However, most known unconventional antiferromagnets do not meet the necessary symmetry requirements for non-relativistic spin current, and this limits applications in spintronic devices. Here we demonstrate crystal-symmetry-paired spin-valley locking in a layered room-temperature antiferromagnetic compound, Rb1-δV2Te2O. Spin-resolved photoemission measurements directly show the opposite spin splitting between crystal-symmetry-paired valleys. Quasi-particle interference patterns show the suppression of intervalley scattering due to the spin selection rules that are a direct consequence of the spin-valley locking. These results suggest that Rb1-δV2Te2O is a potential room-temperature altermagnet candidate. Our observations highlight a methodology that enables both the advantages of layered materials and possible control through crystal symmetry manipulation for advancements in magnetism, electronics and information technology.
Magnetic properties and materials, Spintronics
arXiv
Critical Probability Distributions of the order parameter at two loops II: $O(n)$ universality class
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-03-31 20:00 EDT
We show how to compute the probability distributions of the order parameter of the $O(n)$ model at two-loop order of perturbation theory generalizing the methods developed for computing the same in case of the Ising model \cite{Sahu:2025bkp}. We show that even for the $O(n)$ model, there exists not one but a family of these probability distribution functions indexed by $\zeta$ which is the ratio of system size $L$ to the bulk correlation length $\xi_{\infty}$. We also compare these PDFs to the Monte-Carlo simulations and the existing FRG results \cite{Rancon:2025bjf} for the $O(2)$ and $O(3)$ models.
Statistical Mechanics (cond-mat.stat-mech), High Energy Physics - Theory (hep-th)
13 pages (including the appendix), 7 figures
Thermodynamics of the XX spin chain in the QTM approach
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-03-31 20:00 EDT
The free energy density of the XX chain in magnetic field is obtained in two alternative ways within the Quantum Transfer Matrix approach. In both the cases the proofs are complete and self-consistent. All the intermediate constructions are presented explicitly in detail.
Statistical Mechanics (cond-mat.stat-mech), Strongly Correlated Electrons (cond-mat.str-el), Exactly Solvable and Integrable Systems (nlin.SI)
23 pages
Size-restricted magnetotransport in the delafossite metals PdCoO$_2$ and PtCoO$_2$
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-03-31 20:00 EDT
Michal Moravec, Graham Baker, Maja D. Bachmann, Aaron L. Sharpe, Nabhanila Nandi, Arthur W. Barnard, Carsten Putzke, Seunghyun Khim, Markus König, David Goldhaber-Gordon, Philip J.W. Moll, Andrew P. Mackenzie
Studies of electronic transport in width-restricted channels of PdCoO$_2$ have recently revealed a novel `directional ballistic’ regime, in which ballistic propagation of electrons on an anisotropic Fermi surface breaks the symmetries of bulk transport. Here we introduce a magnetic field to this regime, in channels of PdCoO$_2$ and PtCoO$_2$ along two crystallographically distinct directions and over a wide range of widths. We observe magnetoresistance distinct from that in the bulk, with features strongly dependent on channel orientation and becoming more pronounced the narrower the channel. Comparison to semi-classical theory establishes that magnetoresistance arises from field-induced modification of boundary scattering, and helps connect features in the data with specific electronic trajectories. However, the role of bulk scattering in our measurements is yet to be fully understood. Our results demonstrate that finite-size magnetotransport is sensitive to the anisotropy of Fermi surface properties, motivating future work to fully understand and exploit this sensitivity.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Spontaneous Chern-Euler Duality Transitions
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-03-31 20:00 EDT
Kang Yang, Zhi Li, Peng Xue, Emil J. Bergholtz, Piet W. Brouwer
Topological phase transitions are typically characterized by abrupt changes in a quantized invariant. Here we report a contrasting paradigm in non-Hermitian parity-time symmetric systems, where the topological invariant remains conserved, but its nature transitions between the Chern number, characteristic of chiral transport in complex bands, and the Euler number, which characterizes the number of nodal points in pairs of real bands. The transition features qualitative changes in the non-Abelian geometric phases during spontaneous parity-time symmetry breaking, where different quantized components become mutually convertible. Our findings establish a novel topological duality principle governing transitions across symmetry classes and reveal unique non-unitary features intertwining topology, symmetry, and non-Abelian gauge structure.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Mathematical Physics (math-ph), Optics (physics.optics), Quantum Physics (quant-ph)
5+12 pages, 3 figures
Stochastic 1D search-and-capture as a G/M/c queueing model
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-03-31 20:00 EDT
José Giral-Barajas, Paul C Bressloff
We study the accumulation of resources within a target due to the interplay between continual delivery, driven by 1D stochastic search processes, and the sequential consumption of resources. The assumption of sequential consumption is key because it changes the commonly used $G/M/\infty$ queue to a $G/M/c$ queue. Combining the theory of $G/M/c$ queues with the theory of first-passage times, we derive general conditions for the search process to ensure that the number of resources within the queue converges to a steady state and compute explicit expressions for the mean and variance of the number of resources within the queue at steady state. We then compare the performance of the $G/M/c$ queue with that of the $G/M/\infty$ queue for an increasing number of servers. We extend the model to consider two competing targets and show that, under specific scenarios, an additional target is beneficial to the original target. Finally, we study the effects of multiple searchers. Using renewal theory, we numerically compute the inter-arrival time density for $M$ searchers in the Laplace space, which allows us to exploit the explicit expressions for the steady-state statistics of the number of resources within $G/M/1$ and $G/M/\infty$ queues, and compare their behavior with different numbers of searchers. Overall, the $G/M/c$ queue shows a tighter dependence on the configuration of the search process than the $G/M/\infty$ queue does.
Statistical Mechanics (cond-mat.stat-mech)
35 pages, 12 figures
High thermoelectric power factor in Ni-Fe alloy for active cooling applications
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-03-31 20:00 EDT
Shuai Li, Sree Sourav Das, Haobo Wang, Sujit Bati, Prasanna V. Balachandran, Junichiro Shiomi, Jerrold A. Floro, Mona Zebarjadi
Metallic thermoelectric materials are promising candidates for active cooling applications, where high thermal conductivity and a high thermoelectric power factor are essential to maximize effective thermal conductivity. While metals inherently possess high thermal and electrical conductivities, they typically exhibit low Seebeck coefficients. In this work, we create a database and apply machine learning techniques to identify metallic binary alloys with large Seebeck coefficients. Specifically, we identify Ni-Fe as a promising candidate for active cooling. We then fabricate Ni-Fe ingots and demonstrate thermoelectric power factor values as high as 120 {\mu}W/{cm.K^2} at 200 K for these stable alloys, which are composed of cost-effective and abundant elements. Furthermore, we show that the effective thermal conductivity of these alloys, under small temperature differences, can exceed that of pure copper at temperatures above 250 K.
Materials Science (cond-mat.mtrl-sci)
Quantum Borderlines – Fluctuation Energies in Ultracold Bose Gases
New Submission | Quantum Gases (cond-mat.quant-gas) | 2025-03-31 20:00 EDT
Ultracold Bose gases are many-body systems with well-defined particle interactions that may serve as models for interacting quantum fields. The impact of virtual excitations is studied in the spatial transition zone created by a soft confinement potential that separates a degenerate ideal gas from a dense quasi-condensate. We compute within Bogoliubov theory the contribution of quasi-particles to the surface energy at zero temperature.
Quantum Gases (cond-mat.quant-gas)
7 pages, 3 figures, Focus Issue “Casimir Effect and Its Role in Modern Physics’’
Metallicity-driven polar transitions in topological epilayers
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-03-31 20:00 EDT
Eduardo D. Stefanato, Nicolas M. Kawahala, Bianca A. Kawata, Paulo H. O. Rappl, Eduardo Abramof, Felix G. G. Hernandez
Polar metals, materials that exhibit both electric polarization and high conductivity, can also host topological phases. Because free carriers strongly suppress distortive polar order and change the Fermi level, controlling charge dynamics is crucial for simultaneously tuning ferroelectric and topological phases in the same material. Here, we explore the experimental conditions that enable access to these phases in bismuth-doped Pb$_{1-x}$Sn$_x$Te epilayers. For samples in the topological phase at $x = 0.5$, we use terahertz time-domain spectroscopy to evaluate their complex permittivity as a function of temperature. We observe a non-monotonic variation in carrier concentration with bismuth doping, indicating a change in carrier type. By tracking the transverse optical phonon mode, we identify a ferroelectric phase transition when distortive polar order emerges below a critical temperature that depends on carrier concentration. We show that bismuth doping controls the metallicity-dependent order parameters in the softening and hardening phases. Our work demonstrates a tunable platform for engineering exotic states of matter that integrate metallicity, ferroelectricity and topology.
Materials Science (cond-mat.mtrl-sci), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
21 pages, 7 figures
Most topological orders forbid sign-problem-free quantum Monte Carlo: Nonpositive Gauss sum as an indicator
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-03-31 20:00 EDT
Donghae Seo, Minyoung You, Hee-Cheol Kim, Gil Young Cho
Quantum Monte Carlo is a powerful tool for studying quantum many-body physics, yet its efficacy is often curtailed by the notorious sign problem. In this Letter, we introduce a novel criterion for the “intrinsic” sign problem in two-dimensional bosonic topological orders, which cannot be resolved by local basis transformations or adiabatic deformations of the Hamiltonian. Specifically, we show that a nonpositive higher Gauss sum for a given topological order indicates the presence of an intrinsic sign problem. This condition not only aligns with prior findings but significantly broadens their scope. Using this new criterion, we examine the Gauss sums of all 405 bosonic topological orders classified up to rank 12, and strikingly find that 398 of them exhibit intrinsic sign problems. We also uncover intriguing links between the intrinsic sign problem, gappability of boundary theories, and time-reversal symmetry, suggesting that sign-problem-free quantum Monte Carlo may fundamentally rely on both time-reversal symmetry and gapped boundaries. These results highlight the deep connection between the intrinsic sign problem and fundamental properties of topological phases, offering valuable insights into their classical simulability.
Strongly Correlated Electrons (cond-mat.str-el)
6 pages, 1 figure, supplementary information available
Shape instabilities driven by topological defects in nematic polymer networks
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-03-31 20:00 EDT
Silvia Paparini, Giulio G. Giusteri, L. Angela Mihai
Liquid crystalline networks (LCNs) are stimuli-responsive materials formed from polymeric chains cross-linked with rod-like mesogenic segments, which, in the nematic phase, align along a non-polar director. A key characteristic of these nematic systems is the existence of singularities in the director field, known as topological defects or disclinations, and classified by their topological charge. In this study, we address the open question of modeling mathematically the coupling between mesogens disclination and polymeric network by providing a mathematical framework describing the out-of-plane shape changes of initially flat LCN sheets containing a central topological defect. Adopting a variational approach, we define an energy associated with the deformations consisting of two contributions: an elastic energy term accounting for spatial director variations, and a strain-energy function describing the elastic response of the polymer network. The interplay between nematic elasticity, which seeks to minimize distortions in the director field, variations in the degree of order, with the consequent tendency of monomers in the polymer chains to distribute anisotropically in response to an external stimulus, and mechanical stiffness, which resists deformation, determines the resulting morphology. We analyze the transition to instability of the ground-state flat configuration and characterize the corresponding buckling modes.
Soft Condensed Matter (cond-mat.soft)
Observation of Magnomechanics at Low Temperatures
New Submission | Other Condensed Matter (cond-mat.other) | 2025-03-31 20:00 EDT
Y. Huang, P.M.C Rourke, A. Peruzzi, J. Jin, M. Ebrahimi, A. Rashedi, J. P. Davis
Cavity magnomechanics combines strong coupling between magnons in a dielectric material and microwave cavity photons with long-lived mechanical resonances. Forming a triple resonance condition, this hybrid quantum system promises many advantages in quantum technologies, yet has never been studied at the cryogenic temperatures required to reveal such quantum properties. We report the first observation of magnomechanics at cryogenic temperatures down to 9 K. The experiment was conducted using a YIG sphere inside a microwave cavity, where we measured both the thermomechanical motion and the temperature-dependence of the magnon linewidth.
Other Condensed Matter (cond-mat.other), Quantum Physics (quant-ph)
5 pages, 5 figures
Magnetic polarons due to spin-length fluctuations in $\boldsymbol{d}^\mathbf{4}$ spin-orbit Mott systems
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-03-31 20:00 EDT
Jan Revenda, Krzysztof Wohlfeld, Jiří Chaloupka
Mott insulators based on $4d$ and $5d$ transition-metal ions, where spin-orbit interaction plays a key role, can exhibit various forms of unusual magnetism. A particular example is the antiferromagnet Ca$_2$RuO$_4$ containing $d^4$ Ru$^{4+}$ ions. Here the spin-orbit interaction stabilizes the non-magnetic $J=0$ singlet ionic ground state, which gets dynamically mixed - via exchange interactions - with low-energy $J=1$ ionic excitations. Thanks to a sufficient strength of the exchange, these excitations condense and a long-range order emerges. The resulting ordered moments are soft and prone to fluctuations of their effective length. The corresponding amplitude mode appears as a prominent magnetic excitation and complements the conventional magnons involving rotations of the moments. Motivated by this peculiar kind of magnetic order and the specific spectrum of magnetic excitations, we study their influence on the propagation of doped carriers. To this end, we construct a microscopic model including both $d^4$ and $d^5$ degrees of freedom and address the propagation of an injected electron by employing self-consistent Born approximation. We find that the electron shows a combination of both free and a polaronic type of motion, where the mobile carrier strongly interacts with an accompanying cloud of magnetic excitations. Remarkably, in the latter case it is the exotic excitation - the amplitude mode - that is found to dominate over the contribution of magnons. Our soft-spin situation thus largely contrasts with spin polarons widely discussed in the context of doped Heisenberg-like magnets based on rigid spin moments.
Strongly Correlated Electrons (cond-mat.str-el)
21 pages, 11 figures
Dynasor 2: From Simulation to Experiment Through Correlation Functions
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-03-31 20:00 EDT
Esmée Berger, Erik Fransson, Fredrik Eriksson, Eric Lindgren, Göran Wahnström, Thomas Holm Rod, Paul Erhart
Correlation functions, such as static and dynamic structure factors, offer a versatile approach to analyzing atomic-scale structure and dynamics. By having access to the full dynamics from atomistic simulations, they serve as valuable tools for understanding material behavior. Experimentally, material properties are commonly probed through scattering measurements, which also provide access to static and dynamic structure factors. However, it is not trivial to decode these due to complex interactions between atomic motion and the probe. Atomistic simulations can help bridge this gap, allowing for detailed understanding of the underlying dynamics. In this paper, we illustrate how correlation functions provide structural and dynamical insights from simulation and showcase the strong agreement with experiment. To compute the correlation functions, we have updated the Python package dynasor with a new interface and, importantly, added support for weighting the computed quantities with form factors or cross sections, facilitating direct comparison with probe-specific structure factors. Additionally, we have incorporated the spectral energy density method, which offers an alternative view of the dispersion for crystalline systems, as well as functionality to project atomic dynamics onto phonon modes, enabling detailed analysis of specific phonon modes from atomistic simulation. We illustrate the capabilities of dynasor with diverse examples, ranging from liquid Ni3Al to perovskites, and compare computed results with X-ray, electron and neutron scattering experiments. This highlights how computed correlation functions can not only agree well with experimental observations, but also provide deeper insight into the atomic-scale structure and dynamics of a material.
Materials Science (cond-mat.mtrl-sci), Computational Physics (physics.comp-ph)
13 pages, 7 figures
Petal-Graphyne: A Novel 2D Carbon Allotrope for High-Performance Li and Na Ion Storage
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-03-31 20:00 EDT
Kleuton A. L. Lima, José A. S. Laranjeira, Nicolas F. Martins, Alexandre C. Dias, J ulio R. Sambrano, Douglas S. Galvão, Luiz A. Ribeiro Junior
Using density functional theory simulations, this study introduces Petal-Graphyne (PLG), a novel multi-ring metallic structure composed of 4-, 8-, 10-, and 16-membered rings. Its structural, electronic, and lithium/sodium storage properties were comprehensively investigated. PLG exhibits a high theoretical capacity of 1004 mAh/g for Li, Na, and mixed Li/Na ions, surpassing conventional graphite anodes. The material remains metallic, with multiple band crossings at the Fermi level. The optimal energy barriers for Li (0.28 eV) and Na (0.25 eV) on PLG and favorable diffusion coefficients in both monolayer and multilayer configurations are unveiled. The open circuit voltages are 0.47 V for Li, 0.51 V for Na, and 0.54 V for mixed-ion storage, suggesting stable electrochemical performance. These results highlight PLG as a promising candidate for next-generation lithium and sodium-ion batteries, combining high storage capacity and efficient ion transport.
Materials Science (cond-mat.mtrl-sci), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
13 pages
Rotating anisotropic Bose gas with large number of vortices
New Submission | Quantum Gases (cond-mat.quant-gas) | 2025-03-31 20:00 EDT
Rapidly rotating atomic gases provide a platform for studying phenomena akin to type-II superconductors and quantum Hall systems. Recently, these systems have attracted renewed interest due to technological advances in the trap anisotropy control, in-situ observation capabilities, and cooling and rotating complex atomic species such as dipolar gases. Understanding the vortex lattice formation and quantum melting is crucial for exploring quantum Hall physics in these systems. In this paper, we theoretically investigate the vortex lattices in anisotropic quantum gases. We formulate the rotating gas Hamiltonian in the Landau gauge, and consider the effects of additional perturbations such as the trap potential in the lowest Landau level (LLL). Focusing on the gases with short-range interactions, we obtain the many-body Hamiltonian projected to lowest Landau level. We consider the limit of full Bose-Einstein condensation and obtain the governing Gross-Pitaevskii equation to identify the possible vortex phases. We numerically solve the Gross-Pitaevskii equation using the imaginary time evolution, and demonstrate the possible vortex lattices as a function of anisotropy, rotation speed and interaction strength. We show that the number of states with a support in the LLL, which determines the number of vortices, follows a Thomas-Fermi type scaling albeit with slightly different coefficients from the usual condensates.
Quantum Gases (cond-mat.quant-gas)
14 pages with 4 figures
Sub-nm Curvature Unlocks Exceptional Inherent Flexoelectricity in Graphene
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-03-31 20:00 EDT
Sathvik Ajay Iyengar, James G. McHugh, Jonathan P. Salvage, Robert Vajtai, Alan Dalton, Manoj Tripathi, Pulickel M. Ajayan, Vincent Meunier
Flexoelectricity arises from strain-gradient-induced polarization and is pronounced in two-dimensional (2D) materials due to their mechanical flexibility and sensitivity to structural deformations. This phenomenon approaches its limit in highly curved nanostructures, where extreme charge redistribution and electrostatic modulation result in macroscopic manifestations, such as electronic band offsets, that can be measured. Here, we present the first experimental and theoretical demonstration of giant intrinsic flexoelectricity in graphene nanowrinkles. These nanowrinkles feature a consistent radius of curvature of 5 Å atop a flat MoS_{2} substrate, where strain gradients, mapped by sub-micron Raman spectroscopy, emerge from mismatched elastic properties between graphene and MoS_{2}. Conductive atomic force microscopy (c-AFM) reveals consistent flexoelectric currents over large-area, dense nanowrinkle networks. The observed asymmetric electromechanical behavior, characterized by a threshold potential ({\Phi}_{th}) of ~1 V, suggests an intrinsic energy barrier to activate a flexoelectric current. This threshold likely arises from combined band alignment effects and strain-induced polarization barriers, which modulate carrier transport at the wrinkle apex. Notably, this behavior aligns with our theoretical band offset predictions (1.2 V), further supporting flexoelectric dipoles in modifying local electrostatic potential. This represents the strongest manifestations of flexoelectricity in nanostructures with intrinsic polarization densities 10^{5}-10^{7} times greater than meso/micro counterparts yielding P_{th} ~ 4 C/m^{2}, P_{exp} ~ 1 C/m^{2}. This work establishes graphene nanowrinkles as a model system for exploring giant nanoscale flexoelectric effects and highlights their potential for strain-engineered nanoscale electronic and electromechanical devices.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Materials Science (cond-mat.mtrl-sci)
29 pages, 4 main figures, 11 supplementary figures
Phase-Coherent Dynamics in Intervalley Coherent States
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-03-31 20:00 EDT
Electron transport driven by the phase coherence and interference of quantum many-body wavefunctions is a fascinating phenomenon with potential technological significance. Superconductivity, for example, enables dissipationless transport through macroscopic phase twisting. Similarly, in charge-density waves, once the phase degree of freedom-representing the collective position of electrons relative to the lattice-is depinned, it generates characteristic broadband noise and intriguing AC-DC interference patterns. In this work, we point out a phase-coherent transport phenomena in the intervalley coherent (IVC) state, also known as the bond-ordered or Kekule distorted state, frequently reported in rhombohedral multilayer graphene. Under a static magnetic field, the IVC state responds with an oscillating orbital magnetization, inducing an AC Hall effect similar to the AC Josephson effect in superconductors. In this analogy, the magnetic field acts as the DC voltage, while the oscillating magnetization acts as the AC Josephson current. We present detailed microscopic calculations for all the parameters of the phase-number free-energy in rhombohedral trilayer graphene, predicting an oscillation frequency of approximately 12 GHz at 0.1 Tesla. We comment on this phase-coherent transport in twisted homobilayer transition metal dichalcogenides, where the IVC state has been theoretically proposed.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Materials Science (cond-mat.mtrl-sci), Superconductivity (cond-mat.supr-con)
9 pages, 8 figures
Emergent Hidden Multipolar State in the Triangular Lattice Magnet TmZn2GaO5
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-03-31 20:00 EDT
Matthew Ennis, Rabindranath Bag, Tessa Cookmeyer, Matthew B. Stone, Alexander I. Kolesnikov, Tao Hong, Leon Balents, Sara Haravifard
TmZn2GaO5 is a newly synthesized triangular lattice magnet that exhibits a unique quantum phase characterized by strong Ising anisotropy, a pseudo-doublet crystal electric field ground state, and a low-energy gapped excitation at the K point. Unlike its well-known counterparts, TmMgGaO4 and YbMgGaO4, this material crystallizes in a distinct hexagonal structure, leading to a cleaner platform for investigating frustrated magnetism. Magnetic susceptibility, heat capacity, and inelastic neutron scattering measurements confirm the absence of long-range magnetic order down to 50 mK, placing TmZn2GaO5 in a distinct region of the transverse-field Ising model phase diagram. Theoretical calculations based on spin-wave theory and mean-field modeling reproduce key experimental observations, reinforcing the material’s placement in a quantum disordered/multipolar state. These results highlight its potential for exploring quantum disordered states, anisotropic excitations, and exotic quantum phases in frustrated spin systems.
Strongly Correlated Electrons (cond-mat.str-el), Materials Science (cond-mat.mtrl-sci)
Dynamical phase transition in the growth of programmable polymorphic materials
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-03-31 20:00 EDT
The hallmark feature of polymorphic systems is their ability to assemble into many possible structures at the same thermodynamic state. Designer polymorphic materials can in principle be engineered via programmable self-assembly, but the robustness of the assembly process depends on dynamical factors that are poorly understood. Here we predict a new failure mode for the growth of multicomponent polymorphic materials, in which dynamical coexistence occurs between ordered and disordered assembly trajectories. We show that this transition is preceded by the formation of a steady-state disordered wetting layer, suggesting a nonequilibrium analogy to pre-melting phenomena at equilibrium. This dynamical phase transition is likely to occur in a variety of systems and may fundamentally limit the complexity of polymorphic materials that can be designed through programmable self-assembly.
Soft Condensed Matter (cond-mat.soft)
Includes supplementary information
Infrared Dielectric Function of Photochromic Thiazolothiazole Embedded Polymer
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-03-31 20:00 EDT
Nuren Z. Shuchi, Tyler J. Adams, Naz F. Tumpa, Dustin Louisos, Glenn D. Boreman, Michael G. Walter, Tino Hofmann
In this paper, the infrared dielectric function of photochromic dipyridinium thiazolo[5,4-d]thiazole embedded in polymer is reported. Bulk thiazolo[5,4-d]thiazole-embedded polymer samples were prepared by drop casting and dehydration in room temperature. The samples were investigated using spectroscopic ellipsometry before and after irradiation with a 405~nm diode laser in the infrared spectral range from 500 cm-1 to 1800 cm-1. The model dielectric functions of the thiazolothiazole embedded polymer film for its TTz2+ (unirradiated) and TTz0 (irradiated) states are composed of a series of Lorentz oscillators in the measured spectral range. A comparison of the obtained complex dielectric functions for the TTz2+ and TTz0 states shows that the oscillators located in the spectral ranges 500 cm-1 - 700 cm-1, 1300 cm-1 - 1400 cm-1, and 1500 cm-1 - 1700 cm-1 change in both amplitude and resonant frequency upon transition between the states. Additionally, a resonance at approximately 1050 cm-1 exhibited a change in oscillator amplitude but not resonant frequency due to the photochromic transition.
Materials Science (cond-mat.mtrl-sci), Soft Condensed Matter (cond-mat.soft), Optics (physics.optics)
12 pages, 3 figures
Characterizing the Hyperuniformity of Disordered Network Metamaterials
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-03-31 20:00 EDT
Charles Emmett Maher, Katherine A. Newhall
Advancements in materials design and manufacturing have allowed for the production of ordered and disordered metamaterials with diverse and novel properties. Hyperuniform two-phase heterogeneous materials, which anomalously suppress density fluctuations on large length scales compared to typical disordered systems, and network materials are two classes of metamaterial that have desirable physical properties. Recent focus has been placed on the design of disordered hyperuniform network metamaterials that inherit the desirable properties of both of these metamaterial classes. In this work, we focus on determining the extent to which network structures derived from the spatial tessellations of hyperuniform point patterns inherit the hyperuniformity of the progenitor point patterns. In particular, we examine the Delaunay, Voronoi, Delaunay-Centroidal, and Gabriel tessellations of nonhyperuniform and hyperuniform point patterns in two- and three-dimensional Euclidean space. We use the spectral density to characterize the density fluctuations of two-phase media created by thickening the edges of these tessellations in two dimensions and introduce a novel variance-based metric to characterize the network structures directly in two and three dimensions. We find that, while none of the tessellations completely inherit the hyperuniformity of the progenitor point pattern, the degree to which the hyperuniformity is inherited is sensitive to the tessellation scheme and the short- and long-range translational disorder in the point pattern, but not to the choice of beam shape when mapping the networks into two-phase media.
Soft Condensed Matter (cond-mat.soft)
13 pages, 7 figures
Ground states of quasi-two-dimensional correlated systems via energy expansion
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-03-31 20:00 EDT
Sam Mardazad, Nicolas Laflorencie, Johannes Motruk, Adrian Kantian
We introduce a generic method for computing groundstates that is applicable to a wide range of spatially anisotropic 2D many-body quantum systems. By representing the 2D system using a low-energy 1D basis set, we obtain an effective 1D Hamiltonian that only has quasi-local interactions, at the price of a large local Hilbert space. We apply our new method to three specific 2D systems of weakly coupled chains: hardcore bosons, a spin-$1/2$ Heisenberg Hamiltonian, and spinful fermions with repulsive interactions. In particular, we showcase a non-trivial application of the energy expansion framework, to the anisotropic triangular Heisenberg lattice, a highly challenging model related to 2D spin liquids. Treating lattices of unprecedented size, we provide evidence for the existence of a quasi-1D gapless spin liquid state in this system. We also demonstrate the energy expansion-framework to perform well where external validation is possible. For the fermionic benchmark in particular, we showcase the energy expansion-framework’s ability to provide results of comparable quality at a small fraction of the resources required for previous computational efforts.
Strongly Correlated Electrons (cond-mat.str-el), Superconductivity (cond-mat.supr-con), Computational Physics (physics.comp-ph), Quantum Physics (quant-ph)
Towards Interfacing Dark-Field X-ray Microscopy to Dislocation Dynamics Modeling
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-03-31 20:00 EDT
Axel Henningsson, Sina Borgi, Grethe Winther, Anter El-Azab, Henning Friis Poulsen
Deformation gradient tensor fields are reconstructed in three dimensions (mapping all 9 tensor components) using synthetic Dark-Field X-ray Microscopy data. Owing to the unique properties of the microscope, our results imply that the evolution of deformation fields can now be imaged non-destructively, in situ, and within deeply embedded crystalline elements. The derived regression framework and sampling scheme operate under the kinematic diffraction approximation and are well-suited for studying microstructure evolution during plastic deformation. We derive the deformation conditions under which diffraction vectors extracted from DFXM images can be uniquely associated to the deformation gradient tensor field of the sample. The analysis concludes that the deformation gradient tensor field must vary linearly over line segments defined by the X-ray beam width and the diffracted ray path. The proposed algorithms are validated against numerical simulations for realistic noise levels. Reconstructions of a simulated single straight-edge dislocation show that the Burgers vector components can be recovered with an error of <2%. The mean absolute error of the reconstructed elastic distortion field was found to be <10^-6. By taking the curl of the elastic distortion field, local dislocation densities are derived, yielding a reconstructed dislocation core position with sub-pixel accuracy. The significance of directly measuring the elastic distortion and the dislocation density tensor fields is discussed in the context of continuum theory of dislocations. Such measurements can also be interfaced with continuum dislocation dynamics by providing data that can guide the development and validation, thus extending the relevant models to finite strain regimes.
Materials Science (cond-mat.mtrl-sci)
Superior electrochemical performance of zinc-ion batteries with fine-grained and textured zinc anode produced by high-pressure torsion
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-03-31 20:00 EDT
Xinxin Hu, Shivam Dangwal, Xucheng Wang, Fan Zhang, Haijuan Kong, Jun Li, Kaveh Edalati
Zinc-ion batteries are promising alternatives to lithium-ion batteries, offering advantages in safety, cost, and environmental impact. However, their performance is often limited by the functioning of the zinc anode. This study employs severe plastic deformation via the high-pressure torsion (HPT) method to enhance the electrochemical performance of zinc anodes. HPT reduced the grain size from >1000 {\mu}m to 20 {\mu}m and introduced a (002) basal texture. The battery assembled with HPT-processed zinc demonstrated improved cycling stability, rate performance, and specific discharge capacity (>500 mAh/g at 0.5 A/g after 50 cycles), particularly at high current densities. This performance enhancement was attributed to grain-boundary and texture effects on improved ion transfer (confirmed by electrochemical impedance spectroscopy), fast redox reaction kinetics (confirmed by cyclic voltammetry), and reduced corrosion (confirmed by microscopy and potentiodynamic polarization test). This study highlights the potential of severely deformed materials with textured fine grains for advanced rechargeable battery technologies.
Materials Science (cond-mat.mtrl-sci)
Structure, corrosion resistance and nanomechanical properties of CoCrFeNiX (X=Nb,Mo,B,Si) high entropy alloys
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-03-31 20:00 EDT
Rafal Babilas, Jakub Bicz, Adrian Radon, Mariola Kadziolka-Gawel, Dariusz Lukowiec, Krzysztof Matus, Edyta Wyszkowska, Lukasz Kurpaska, Darya Rudomilova, Katarzyna Mlynarek-Zak
In this work, the four high entropy CoCrFeNiX alloys (X=Mo,Nb,B,Si) were prepared by induction melting to comparatively analyse their structure, nanomechanical properties, and corrosion resistance in the chloride ion environment. The CoCrFeNiNb and CoCrFeNiMo alloys are composed of FCC solid solution and intermetallic phases (TM)2Nb and Cr-Mo-TM. In the case of the CoCrFeNiB alloy, a complex phase structure was revealed, consisting of FCC solid solution and three types of borides. In turn, the addition of Si substantially altered the phase composition of the CoCrFeNi alloy, resulting in the formation of two intermetallic phases. The corrosion behaviour of the alloys was studied in 3.5 and 5% NaCl solutions. The highest corrosion resistance in both solutions used characterize the CoCrFeNiSi alloy, showing the lowest corrosion current density and the most positive corrosion potential values. For measurements in 5% NaCl solution, icorr and Ecorr were equal to 0.24 microA/cm2 and -0.136 V. Currently, the least favourable corrosion parameters were recorded for the CoCrFeNiMo alloy. The results of EIS measurements confirmed the high protective abilities of passive film formed on the CoCrFeNiSi alloy surface. The highest strength properties were shown by the alloys with the addition of metalloids. For the CoCrFeNiSi alloy, the highest nanohardness value was obtained (above 15 GPa), while the CoCrFeNiB showed the highest Young modulus (above 275 GPa).
Materials Science (cond-mat.mtrl-sci)
17 pages, 17 figures, 7 tables
Electrochimica Acta, Volume 525, 10 June 2025, 145933
Interplay between inversion and translation symmetries in trigonal PtBi$_2$
New Submission | Superconductivity (cond-mat.supr-con) | 2025-03-31 20:00 EDT
Santiago Palumbo, Pablo S. Cornaglia, Jorge I. Facio
The trigonal Weyl semimetal PtBi$_2$ presents an intriguing superconducting phase, previously reported to be confined to its topological Fermi arcs within a certain temperature range. This observation highlights the importance of a thorough understanding of its normal phase, particularly the roles that spin-orbit coupling (SOC) and inversion-symmetry breaking play in shaping its band structure. Our density-functional theory calculations reveal that the semimetallic nature of trigonal PtBi$_2$ can be interpreted as stemming from a noncentrosymmetric crystal distortion of a parent structure, that drives a metal to semimetal transition. This distortion breaks inversion symmetry and, crucially, reduces translational symmetry. Due to its interplay with translational symmetry, inversion-symmetry breaking emerges as the dominant energy scale producing substantial asymmetries ($\sim$ 0.6,eV) in certain short-range hopping amplitudes, superseding the effects of SOC, whose primary role is to define the characteristics of the low-energy nodal structure. This also applies to the formation of the Weyl nodes closest to the Fermi energy, which are found to exist even in the absence of SOC as a result of the orbital physics associated with the reduced translational symmetry.
Superconductivity (cond-mat.supr-con), Other Condensed Matter (cond-mat.other)
Comments are welcome
Many-body Localization in a Slowly Varying Potential
New Submission | Disordered Systems and Neural Networks (cond-mat.dis-nn) | 2025-03-31 20:00 EDT
Zi-Jian Li, Yi-Ting Tu, Sankar Das Sarma
We study many-body localization (MBL) in a nearest-neighbor hopping 1D lattice with a slowly varying (SV) on-site potential $U_j = \lambda\cos(\pi\alpha j^s)$ with $0<s<1$. The corresponding non-interacting 1D lattice model is known to have single-particle localization with mobility edges. Using exact diagonalization, we find that the MBL of this model has similar features to the conventional MBL of extensively studied random or quasiperiodic (QP) models, including the transitions of eigenstate entanglement entropy (EE) and level statistics, and the logarithmic growth of EE. To further investigate the universal properties of this MBL transition in the asymptotic regime, we implement a real-space renormalization group (RG) method. RG analysis shows a subvolume scaling $\sim L^{d_{\rm MBL}}$ with $d_{\rm MBL} \approx 1-s$ of the localization length (length of the largest thermal clusters) in this MBL phase. In addition, we explore the critical properties and find universal scalings of the EE and localization length. From these quantities, we compute the critical exponent $\nu$ using different parameters $s$ (characterizing different degrees of spatial variation of the imposed potential), finding the critical exponent staying around $\nu\approx2$. This exponent $\nu \approx 2$ is close to that of the QP model within the error bars but differs from the random model. This observation suggests that the SV model and the QP model may belong to the same universality class, which is, however, likely distinct from the random universality class.
Disordered Systems and Neural Networks (cond-mat.dis-nn), Statistical Mechanics (cond-mat.stat-mech), Quantum Physics (quant-ph)
14 pages,13 figures
Growth of uniform helium submonolayers adsorbed on single-surface graphite observed by surface X-ray diffraction
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-03-31 20:00 EDT
Atsuki Kumashita, Hiroo Tajiri, Jun Usami, Yu Yamane, Shigeki Miyasaka, Hiroshi Fukuyama, Akira Yamaguchi
We observed surface X-ray diffraction from He-4 submonolayers adsorbed on a single-surface graphite using synchrotron X-rays. Time evolutions of scattering intensities along the crystal truncation rod (CTR) were observed even after reaching the base low temperature in a selected condition of sample preparation. Our simulations for CTR scatterings based on the random double-layer model, in which helium atoms are distributed randomly in the first and second layers with a certain occupancy ratio, can consistently explain the observed intensity changes. These results support the scenario that He atoms are stratified initially as a nonequilibrium state and then relaxed into a uniform monolayer by surface diffusion, where the relaxation process was observed as a decrease in CTR scattering intensity. The observed time constant was, however, much longer than those estimated from quantum and thermal surface diffusions. This implies homogeneous processes in surface diffusions were strongly suppressed by local potentials in such as atomic steps or microcrystalline boundaries.
Materials Science (cond-mat.mtrl-sci), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
9 pages, 3 figures, to be published in Journal of Low Temperature Physics
Optically Controlled Topological Phases in the Deformed $α$-$% T_{3}$ Lattice
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-03-31 20:00 EDT
Othmane Benhaida, Saidi El Hassan, L. B. Drissi
Haldane’s tight-binding model, which describes a Chern insulator in a two-dimensional hexagonal lattice, exhibits quantum Hall conductivity without an external magnetic field. Here, we explore an $\alpha -T_{3}$ lattice subjected to circularly polarized off-resonance light. This lattice, composed of two sublattices (A and B) and a central site (C) per unit cell, undergoes deformation by varying the hopping parameter $\gamma _{1}$ while keeping $\gamma _{2}$= $\gamma {3}$= $\gamma $. Analytical expressions for quasi-energies in the first Brillouin zone reveal significant effects of symmetry breaking. Circularly polarized light lifts the degeneracy of Dirac points, shifting the cones from M. This deformation evolves with $\gamma {1} $, breaking symmetry at $\gamma {1}=2\gamma $, as observed in Berry curvature diagrams. In the standard case ($\gamma {1}=\gamma $), particle-hole and inversion symmetries are preserved for $\alpha =0$ and $% \alpha =1$. The system transitions from a semi-metal to a Chern insulator, with band-specific Chern numbers: $C{2}=1$, $C{1}=0$, and $C{0}=-1$ for $% \alpha <1/\sqrt{2},$ shifting to $C_{2}=2$, $C_{1}=0$, and $C_{0}=-2$ when $% \alpha \geqslant 1/\sqrt{2}.$For $\gamma _{1}>2\gamma $, the system enters a trivial insulating phase. These transitions, confirmed via Wannier charge centers, are accompanied by a diminishing Hall conductivity. Our findings highlight tunable topological phases in $\alpha -T{3}$ lattices, driven by light and structural deformation, with promising implications for quantum materials.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Spin-Polarized Antiferromagnetic Spintronics
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-03-31 20:00 EDT
Zhenzhou Guo, Xiaotian Wang, Wenhong Wang, Gang Zhang, Xiaodong Zhou, Zhenxiang Cheng
Spin-polarized antiferromagnets (AFMs), including altermagnets, noncollinear AFMs, and two-dimensional layer-polarized AFMs, have emerged as transformative materials for next-generation spintronic and optoelectronic technologies. These systems uniquely combine spin-polarized electronic states with vanishing net magnetization, enabling ultrafast spin dynamics, high-density integration, and robustness against stray magnetic fields. Their unconventional symmetry-breaking mechanisms-governed by crystal symmetry, chiral spin textures, or interlayer potential control-give rise to emergent phenomena previously exclusive to ferromagnets: nonrelativistic spin-momentum locking, spontaneous anomalous transport phenomena, gate-tunable magneto-optical responses, and nonrelativistic spin-polarized current. This review systematically examines the fundamental principles linking symmetry, band topology, and transport properties across these material classes, synthesizing recent breakthroughs in both theory and experiment. We further identify critical challenges in achieving room-temperature functionality, scalable Neel vector control, and coherent spin-current manipulation, while outlining pathways to harness these materials for ultra-low-power memory, spin-logic architectures, and quantum information technologies.
Materials Science (cond-mat.mtrl-sci)
First-Principles Investigation of Auxetic Piezoelectric Effect in Nitride Perovskites
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-03-31 20:00 EDT
Yanting Peng, Zunyi Deng, Siyu Song, Gang Tang, Jiawang Hong
The recently reported auxetic piezoelectric effect, which acts as the electrical counterpart of the negative Poisson’s ratio, is of significant technical importance for applications in acoustic wave devices. However, this electric auxetic effect has not yet been reported in perovskite systems. In this work, we employ first-principles calculations to investigate the piezoelectric properties of six polar nitride perovskites with the chemical formula ABN3 (A = La, Sc, Y; B = W, Mo). Among these, all compounds except ScMoN3 exhibit the auxetic piezoelectric effect, which is characterized by an unusually positive transverse piezoelectric coefficient, along with a positive longitudinal piezoelectric coefficient. This behavior is in sharp contrast to previously reported results in HfO2, where both the longitudinal and transverse piezoelectric coefficients are negative. These unusual positive transverse piezoelectric coefficients originate from the domination of the positive internal-strain contribution. We further confirm the auxetic piezoelectric effect with finite electric field calculations. Our research enriches the understanding of the piezoelectric properties of nitride perovskites and provides a new compositional space for the design of novel auxetic piezoelectric materials.
Materials Science (cond-mat.mtrl-sci), Computational Physics (physics.comp-ph)
17 pages, 9 figures
Non-resonant inter-species interaction and its effect on the position response function of cold atoms
New Submission | Quantum Gases (cond-mat.quant-gas) | 2025-03-31 20:00 EDT
Anirban Misra, Urbashi Satpathi, Supurna Sinha, Sanjukta Roy, Saptarishi Chaudhuri
In the context of non-equilibrium statistical physics, the position response of a particle, coupled to a bath, subjected to an external force is a topic of broad interest. A topic of further interest is two distinguishable sets of interacting particles in contact with two different baths. Here, we report the experimental evidence of the modification of the position response function (PRF) of an ensemble of cold atoms in a magneto-optical trap when it is placed alongside a dilute cloud of cold atoms of a different species. Our experiment consists of a mass-imbalanced cold atomic mixture of Potassium and Sodium atoms. We focus on the position response of Potassium atoms when subjected to a sudden displacement in the presence of a cold Sodium atomic cloud. Notably, we find that, in the underdamped regime of motion, the oscillation frequency of motion of the cold atoms changes as much as 30 $%$ depending on the effective inter-species light-assisted interaction strength. On the other hand, in the overdamped regime, there is a reduction, as high as 10.5 $%$ in the damping coefficient, depending on the interaction strength. Using a quantum Langevin approach, we develop a framework that aligns well with experimental results, with potential applications in mass and charge transport studies under varied physical conditions simulated in cold atoms.
Quantum Gases (cond-mat.quant-gas), Statistical Mechanics (cond-mat.stat-mech), Atomic Physics (physics.atom-ph), Quantum Physics (quant-ph)
21 pages, 6 figures
Static and hydrodynamic periodic structures induced by AC electric fields in the antiferroelectric SmZA phase
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-03-31 20:00 EDT
K. S. Krishnamurthy, S. Krishna Prasad, D. S. Shankar Rao, R. J. Mandle, C. J. Gibb, J. Hobbs, N. V. Madhusudana
We report the effect of AC electric fields in the range of 0.1-300 kHz on planar antiferroelectric SmZA layers of DIO. Significant results are (a) primary bifurcation into a quasistationary periodic instability with its voltage threshold Uc and wave vector qc along the initial director being, respectively, quadratic and linear functions of f over 10-150 kHz, and with an azimuthal distortion of the director which changes sign between adjacent stripes, (b) transition from the modulated planar state to a homogeneous state at higher voltages, and (c) third bifurcation into travelling wave periodic state on further rise in U in the region 10-40 kHz. We interpret these findings as follows. The low voltage instability is very similar to that seen in the higher temperature apolar nematic phase, and is the electrohydrodynamic (EHD) instability possibly belonging to the region of dielectric inversion frequency. The azimuthal distortions of n result from an undulatory distortion of the SmZA layers in the book-shelf geometry. The intermediate homogeneous state of SmZA in which the periodic structure is absent results from a linear coupling between the layer polarization P and applied field E, giving rise to a scissoring type mutual P reorientation in adjacent layers. Finally, at even higher voltages, the medium goes over to a field induced transition to the ferroelectric nematic, with the polarization following the AC field, and the periodic EHD instability being similar to that of the dielectric regime. The polar vector symmetry of the medium leads in general to travelling waves.
Soft Condensed Matter (cond-mat.soft)
22 pages, 20 figures, paper under review in Phys Rev E
Host dependence of PL5 ensemble in 4H-SiC
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-03-31 20:00 EDT
Jiajun Li, Hui Qi, Feifei Zhou, Yumeng Song, Nanyang Xu, Bo Hong, Hongwei Chen, Ying Dong, Xinqing Wang
Color center PL5 in 4H silicon carbide (4H-SiC) has drawn significant attention due to its room-temperature quantum coherence properties and promising potential of quantum sensing applications. The preparation of PL5 ensemble is a critical prerequisite for practical applications. In this work, we investigated the formation of PL5 ensembles in types of 4H-SiC wafers, focusing on their suitability as hosts for PL5 ensemble. Results demonstrate that PL5 signals are exclusively observed in high-purity semi-insulating (HPSI) substrates, whereas divacancies PL1-PL4 can be detected in both HPSI and epitaxial samples. The type of in-plane stress in HPSI and epitaxial hosts is compressive in the same order of magnitude. Defects like stacking faults and dislocations are not observed simultaneously in the PL5 ensemble. Notably, the PL5 ensemble exhibits a relatively uniform distribution in the HPSI host, highlighting its readiness for integration into quantum sensing platforms. Furthermore, signal of PL5 can always be detected in the HPSI samples with different doses of electron irradiation, which suggests that HPSI wafers are more suitable hosts for the production of PL5 ensemble. This work provides critical insights into the material-specific requirements for PL5 ensemble formation and advances the development of 4H-SiC-based quantum technologies.
Materials Science (cond-mat.mtrl-sci)
12 pages, 5 figures
Low-energy excitations in multiple modulation-doped CdTe/(CdMg)Te quantum wells
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-03-31 20:00 EDT
D. Yavorskiy, F. Le Mardelé, I. Mohelsky, M. Orlita, Z. Adamus, T. Wojtowicz, J. Wróbel, K. Karpierz, J. Łusakowski
Low energy excitations of a two-dimensional electron gas (2DEG) in modulation-doped multiple (ten) quantum wells (QWs) was studied using far-infrared magneto-transmission technique at liquid helium temperatures. A large distance between neighbouring QWs of 54 nm excluded a direct interaction of electron wave functions confined in the wells. In four samples which differed in the spacer width and the level of doping with iodine donors, supplied with a metallic grid coupler, a uniform picture of exitations of the 2DEG was observed. These involved the cyclotron resonance (CR), its second harmonic (2CR) and magnetoplasmon modes (MPMs). MPMs with a small amplitude originated from excitations of the 2DEG in a single QW and these with a high amplitude resulted from a coherent excitation of the 2DEG in all wells. A polaron effect resulting from the interaction of the CR, 2CR and MPMs with an optical phonon was observed and discribed with appropriate models. Both types of MPMs exhibited gaps in the disperion relations at the frequency close to the 2CR, leading to Bernstein modes, which was discribed with an appropriate (non-local) theoretical model.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Materials Science (cond-mat.mtrl-sci)
Strain distribution in GaN/AlN superlattices grown on AlN/sapphire templates: comparison of X-ray diffraction and photoluminescence studies
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-03-31 20:00 EDT
Aleksandra Wierzbicka, Agata Kaminska, Kamil Sobczak, Dawid Jankowski, Kamil Koronski, Pawel Strak, Marta Sobanska, Zbigniew R. Zytkiewicz
Series of GaN/AlN superlattices (SLs) with various periods and the same thicknesses of GaN quantum wells and AlN barriers have been investigated. X-ray diffraction, photoluminescence (PL) and transmission electron microscopy (TEM) techniques were used to study the influence of thickness of AlN and GaN sublayers on strain distribution in GaN/AlN SL structures. Detailed X-ray diffraction measurements demonstrate that the strain occurring in SLs generally decreases with an increase of well/barrier thickness. Fitting of X-ray diffraction curves allowed determining the real thicknesses of the GaN wells and AlN barriers. Since blurring of the interfaces causes deviation of calculated data from experimental results the quality of the interfaces has been evaluated as well and compared with results of TEM measurements. For the samples with thinner wells/barriers the presence of pin-holes and threading dislocations has been observed in TEM measurements. The best quality of interfaces has been found for the sample with a well/barrier thickness of 3 nm. Finally, PL spectra showed that due to Quantum-Confined Stark Effect the PL peak energies of the SLs decreased with increasing the width of the GaN quantum wells and AlN barriers. The effect is well modelled by ab initio calculations based on the density functional theory applied for tetragonally strained structures of the same geometry using a full tensorial representation of the strain in the SLs.
Materials Science (cond-mat.mtrl-sci), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Acta Crystallographica B, Journal logo Structural Science, Crystal Engineering and Materials, B81 (2025)
Bond-dependent interactions and ill-ordered state in the honeycomb cobaltate BaCo$_2$(AsO$_4$)$_2$
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-03-31 20:00 EDT
A. Devillez, J. Robert, E. Lhotel, R. Ballou, C. Cavenel, F. Denis Romero, Q. Faure, H. Jacobsen, J. Lass, D. G. Mazzone, U. Bengaard Hansen, M. Enderle, S. Raymond, S. De Brion, V. Simonet, M. Songvilay
The ground state and Hamiltonian of the honeycomb lattice material BaCo${2}$(AsO${4}$)${2}$ hosting magnetic Co$^{2+}$, have been debated for decades. The recent proposal for anisotropic bond-dependent interactions in such honeycomb cobaltates has raised the prospect of revisiting its Hamiltonian in the context of Kitaev physics. To test this hypothesis, we have combined magnetization, ac-susceptibility and neutron scattering measurements on a BaCo${2}$(AsO${4}$)${2}$ single-crystal, together with advanced modeling. Our experimental results highlight a collinear magnetic ground state with intrinsic disorder associated to an average incommensurate propagation vector. Monte Carlo simulations and linear spin wave calculations were performed to obtain a spin model compatible with this unusual ground state, the dispersion of magnetic excitations and a magnetization plateau under magnetic field. We thus show that bond-dependent anisotropic interactions, including Kitaev-like interactions, are necessary to account for the puzzling properties of this long-explored material, and are hence a general ingredient in the cobaltates.
Strongly Correlated Electrons (cond-mat.str-el)
Theory of polarization-dependent phonon pumping in ferromagnetic/non-magnetic bilayers
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-03-31 20:00 EDT
Mikhail Cherkasskii, Fabian Engelhardt, Manuel Müller, Johannes Weber, Matthias Althammer, Sebastian T. B. Goennenwein, Hans Huebl, Silvia Viola Kusminskiy
We develop a theoretical model for polarization-selective phonon pumping induced by magnon-phonon coupling in a ferromagnetic/non-magnetic acoustic bilayer structure, focusing on the effects arising from a misalignment between the magnetic and crystallographic symmetry axes. Our model considers the coupled equations of motion describing uniform magnetization dynamics (the Kittel mode) and elastic waves in both layers, incorporating phonon pumping and boundary conditions at the interface. We show that even small misalignments lift the degeneracy of transverse shear elastic modes, resulting in phononic birefringence characterized by distinct propagation velocities for linearly polarized modes. Furthermore, our analysis reveals that magnon-phonon hybridization gives magnetic-field-dependent properties to otherwise non-magnetic phonons. We show that the polarization transfer between linearly polarized phonons and the circularly polarized Kittel mode can be tuned with an external magnetic field. Our theoretical results quantitatively reproduce recent experimental findings [1].
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
ML-based Method for Solving the Microkinetic Model of Fischer-Tropsch Synthesis with Varying Catalyst/Reactor Parameters
New Submission | Disordered Systems and Neural Networks (cond-mat.dis-nn) | 2025-03-31 20:00 EDT
Taras Demchuk, Tymofii Nikolaienko, Aniruddha Panda, Subodh Madhav Joshi, Stanislav Jaso, Kaushic Kalyanaraman
This study introduces a physics-informed machine learning framework to accelerate the computation of the microkinetic model of Fischer-Tropsch synthesis. A neural network, trained within the NVIDIA Modulus framework, approximates the fraction of vacant catalytic sites with high accuracy. The combination of implicit differentiation and the Newton-Raphson method enhances derivative calculations, ensuring physical consistency. Computational efficiency improves significantly, with speedups up to $ 10^4 $ times on a GPU. This versatile methodology generalizes across catalysts and reactors, offering a robust tool for chemical engineering applications, including model approximation and catalyst parameter fitting from experimental data.
Disordered Systems and Neural Networks (cond-mat.dis-nn), Chemical Physics (physics.chem-ph)
Quantum transport in SnTe nanowire devices
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-03-31 20:00 EDT
Femke J. Witmans, Mathijs G. C. Mientjes, Maarten J. G. Kamphuis, Vince van de Sande, Xin Guan, Hans Bolten, Marcel A. Verheijen, Chuan Li, Joost Ridderbos, Erik P. A. M. Bakkers, Alexander Brinkman, Floris A. Zwanenburg
We report on a variety of quantum transport experiments in SnTe nanowire devices. Research on these particular nanowire devices is relevant because of their topological properties and their potential to distinguish surface states owing to their high surface-to-volume ratio that suppresses the bulk contribution to the conductance. We observe a low-resistance and a high-resistance regime. The highly resistive devices display semiconducting and quantum dot behavior caused by microscopic differences in the fabrication, while devices with low resistance show partial superconductivity when in a hybrid superconductor-nanowire configuration or Fabry-Pérot oscillations. The latter suggests quantum interference in a ballistic transport channel, attributed to the 2D surface states in SnTe. The wide variety of quantum transport phenomena demonstrate SnTe nanowires as a promising platform for diverse follow-up experiments and novel device architectures, including the exploration of topological superconductivity and the development of low-energy spintronic devices.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Materials Science (cond-mat.mtrl-sci)
Inertia-induced mechanism for giant enhancement of transport generated by active fluctuations
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-03-31 20:00 EDT
Active matter is one of the hottest topics in physics nowadays. As a prototype of living systems operating in viscous environments it has usually been modeled in terms of the overdamped dynamics. Recently, active matter in the underdamped regime has gained a place in the spotlight. In this work we unveil another remarkable face of active matter. In doing so we demonstrate and explain an inertia-induced mechanism of giant enhancement of transport driven by active fluctuations which does emerge neither in the overdamped nor in the underdamped limit but occurs exclusively in the strong damping regime. It may be relevant not only for living systems where fluctuations generated by the metabolism are active by default but also for artificial ones, in particular for designing ultrafast micro and nano-robots. Our findings open new avenues of research in a very vibrant field of active matter.
Statistical Mechanics (cond-mat.stat-mech), Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Soft Condensed Matter (cond-mat.soft)
Uncertainty Quantification in Multiscale Models of Charge Transport in Organic Semiconductors: Influence of the Exhange-Correlation Functional
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-03-31 20:00 EDT
Zhongquan Chen, Pim van der Hoorn, Bjoern Baumeier
This study investigates the impact of exchange-correlation functional choices on the predictive accuracy of multiscale models for charge transport in organic semiconductors (OSCs). A hybrid functional approach is applied to analyze uncertainties in key parameters influencing charge mobility, focusing on the Hartree–Fock exchange fraction. Using 2-methyl-9,10-bis(naphthalen-2-yl)anthracene (MADN) as a test system, molecular dynamics and density functional theory are combined to compute reorganization energies, site energies, and electronic coupling elements. Monte Carlo sampling quantifies the uncertainty propagation, revealing that site energy variations dominate transport property uncertainties, while coupling elements contribute minimally. The findings underscore the need for accurate parameter determination and functional selection, with implications for enhancing the reliability of first-principles-based multiscale modeling frameworks in OSC design.
Materials Science (cond-mat.mtrl-sci)
Thermodynamic anomalies in overdamped systems with time-dependent temperature
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-03-31 20:00 EDT
Shakul Awasthi, Hyunggyu Park, Jae Sung Lee
One of the key objectives in investigating small stochastic systems is the development of micrometer-sized engines and the understanding of their thermodynamics. However, the primary mathematical tool used for this purpose, the overdamped approximation, has a critical limitation: it fails to fully capture the thermodynamics when the temperature varies over time, as the velocity is not considered in the approximation. Specifically, we show that heat dissipation and entropy production calculated under the overdamped approximation deviate from their true values. These discrepancies are termed thermodynamic anomalies. To overcome this limitation, we analytically derive expressions for these anomalies in the presence of a general time-varying temperature. One notable feature of the result is that high viscosity and small mass, though both leading to the same overdamped dynamic equations, result in different thermodynamic anomaly relations. Our results have significant implications, particularly for accurately calculating the efficiency of heat engines operating in overdamped environments with time-varying temperatures, without requiring velocity measurements. Additionally, our findings offer a simple method for estimating the kinetic energy of an overdamped system.
Statistical Mechanics (cond-mat.stat-mech)
21 pages, 5 figures
A Morphotropic Phase Boundary in MA$_{1-x}$FA$_x$PbI$_3$: Linking Structure, Dynamics, and Electronic Properties
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-03-31 20:00 EDT
Tobias Hainer, Erik Fransson, Sangita Dutta, Julia Wiktor, Paul Erhart
Understanding the phase behavior of mixed-cation halide perovskites is critical for optimizing their structural stability and optoelectronic performance. Here, we map the phase diagram of MA$_{1-x}$FA$_x$PbI$_3$ using a machine-learned interatomic potential in molecular dynamics simulations. We identify a morphotropic phase boundary (MPB) at approximately 27% FA content, delineating the transition between out-of-phase and in-phase octahedral tilt patterns. Phonon mode projections reveal that this transition coincides with a mode crossover composition, where the free energy landscapes of the M and R phonon modes become nearly degenerate. This results in nanoscale layered structures with alternating tilt patterns, suggesting minimal interface energy between competing phases. Our results provide a systematic and consistent description of this important system, complementing earlier partial and sometimes conflicting experimental assessments. Furthermore, density functional theory calculations show that band edge fluctuations peak near the MPB, indicating an enhancement of electron-phonon coupling and dynamic disorder effects. These findings establish a direct link between phonon dynamics, phase behavior, and electronic structure, providing a further composition-driven pathway for tailoring the optoelectronic properties of perovskite materials. By demonstrating that phonon overdamping serves as a hallmark of the MPB, our study offers new insights into the design principles for stable, high-performance perovskite solar cells.
Materials Science (cond-mat.mtrl-sci), Computational Physics (physics.comp-ph)
11 pages, 6 figures
Insights on the role of the covalent Ni-O bonds in LiNiO2 positive electrodes: A combined hard X-ray spectroscopy study
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-03-31 20:00 EDT
Jazer Jose H. Togonon, Jean-Noel Chotard, Alessandro Longo, Lorenzo Stievano, Laurence Croguennec, Antonella Iadecola
The interest in Ni-rich layered oxide positive electrode materials has been increasing due to its wide applicability particularly in electric vehicles as high capacity and high energy density electrode materials. However, the Ni-O bond array which builds the overall framework and plays a critical role in the charge compensation mechanism of the material requires deeper understanding. This work presents a correlative approach elucidating the role of the local highly covalent Ni-O bonds in LiNiO2 (LNO) model material. Pristine and electrochemically obtained LNO positive electrodes are analyzed using ex situ X-ray diffraction (XRD) and extended X-ray absorption fine structure (EXAFS) to compare the average and local structural evolution upon Li+ ion de-intercalation. Insights from Ni K-edge X-ray absorption near-edge structure (XANES) and non-resonant Ni Kbeta X-ray emission spectroscopy (XES) spectra are combined to track the electronic environment of Ni. X-ray Raman scattering (XRS) spectra at the Ni L2,3-edges and O K-edge provide direct bulk electronic information with regards to the interplay between Ni 3d and O 2p states. The overall findings imply that O plays a significant role in the charge compensation process, contributing to the substantial negative charge transfer from the O 2p orbitals, because of the covalency in the Ni-O bonds inside the NiO2 framework within the edge-sharing NiO6 octahedra. The utilization of complementary X-ray spectroscopy techniques clarifies the intricate electronic environment of LNO, which is helpful in understanding Ni-rich positive electrode materials and offering new insights into their covalent nature.
Materials Science (cond-mat.mtrl-sci)
Observation of quasi bound states in open quantum wells of cesiated p-doped GaN surfaces
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-03-31 20:00 EDT
Mylène Sauty, Jean-Philippe Banon, Nicolas M. S. Lopes, Tanay Tak, James S. Speck, Claude Weisbuch, Jacques Peretti
The quantized electron states in the downward band bending region (BBR) at the surface of cesiated p-type GaN are investigated. We theoretically predict the existence of metastable resonant states in the BBR with an intrinsic life-time around 20 fs. Their experimental observation requires access to the empty conduction band of the cesiated semiconductor, which is possible with near-bandgap photoemission spectroscopy. The energy distribution of the photoemitted electrons shows contributions coming from electrons accumulated into the resonant states at energies which agree with calculations.
Materials Science (cond-mat.mtrl-sci)
Strain induced stabilization of high symmetry phase in MAPbBr3 perovskite
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-03-31 20:00 EDT
Shankar Dutt, Joydipto Bhattacharya, Kailash Kumar, Rajashri Urkude, Pankaj R. Sagdeo, Archna Sagdeo
Structural phase transitions in the organic inorganic metal halide perovskites are driven via rearrangement of methylammonium cation and distortion in the PbX6 octahedra. Compositional tuning is usually incorporated for suppression of the structural phase transition in these systems with cation or anion tuning. Along with the compositional tuning, behaviour of strain present in the system can also lead to stabilization of single phase in these systems. In the present investigation, two different samples of CH3NH3PbBr3 perovskite were studied and it is observed that structural phase transition is absent for one of the sample while it is present in the other sample. The non-observance of structural phase transition and stabilization of single phase has been attributed to the perceived tensile strain in the system contrary to the compressive strain observed in the system showing structural phase transitions. This observation is further supported by theoretical calculations. Extended X-ray absorption fine structure measurements revealed distorted octahedra with varying bond lengths along planar and axial directions in both samples, along with observed increase in bond lengths in one of the sample. This stabilization of the cubic phase can enhance device performance and increase overall environmental stability, making these systems more effective for practical applications.
Materials Science (cond-mat.mtrl-sci)
The Hungry Daemon: An energy-harvesting active particle must obey the Second Law of Thermodynamics
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-03-31 20:00 EDT
Simon Bienewald, Diego Marcel Fieguth, James R. Anglin
Thought experiments like Maxwell’s Demon or the Feynman-Smoluchowski Ratchet can help in pursuing the microscopic origin of the Second Law of Thermodynamics. Here we present a more sophisticated physical system than a ratchet, consisting of a Hamiltonian active particle which can harvest energy from an environment which may be in thermal equilibrium at a single temperature. We show that while a phenomenological description would seem to allow the system to operate as a Perpetual Motion Machine of the Second Kind, a full mechanical analysis confirms that this is impossible, and that perpetual energy harvesting can only occur if the environment has an energetic population inversion similar to a lasing medium.
Statistical Mechanics (cond-mat.stat-mech), Classical Physics (physics.class-ph)
9 pages, 3 figures
Quantitative characterization of hydrophobic agglomeration at different mixing intensities using a copula-based probabilistic modeling approach
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-03-31 20:00 EDT
Niklas Eiermann, Orkun Furat, Jan Nicklas, Urs A. Peuker, Volker Schmidt
The agglomeration of small poorly wetted alumina particles in a stirred tank is investigated. For different experimental conditions, two bivariate probability densities for the area-equivalent diameter and aspect ratio of primary particles and agglomerates, respectively, are determined, using 2D image data from an inline camera system. Throughout each experiment, these densities do not change since the geometries of primary particles are unaffected by the experimental conditions, while large agglomerates fragment into multiple smaller ones, which results in an equilibrium state regarding the distribution of agglomerate descriptors. Mixtures of these densities are used to model the contents of the stirred tank at each time step of the experiments. Analytical functions, whose parameters characterize the agglomeration dynamics, are fitted to the time-dependent weights of these mixtures. This enables a quantitative comparison of agglomeration processes, highlighting the impact of mixing intensity on the joint distribution of agglomerate descriptors.
Soft Condensed Matter (cond-mat.soft)
Magnetic Resonance Particle Tracking
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-03-31 20:00 EDT
Mathieu Suter, Jens P. Metzger, Andreas Port, Christoph R. Müller, Klaas P. Pruessmann
Granular materials such as gravel, cereals, or pellets, are ubiquitous in nature, daily life, and industry. While sharing some characteristics with gases, liquids, and solids, granular matter exhibits a wealth of phenomena that defy these analogies and are yet to be fully understood. Advancing granular physics requires experimental observation at the level of individual particles and over a wide range of dynamics. Specifically, it calls for the ability to track large numbers of particles simultaneously, in three dimensions (3D), and with high spatial and temporal resolution. Here, we introduce magnetic resonance particle tracking (MRPT) and show it to achieve such recording with resolution on the scale of micrometers and milliseconds. Enabled by MRPT, we report the direct study of granular glassy dynamics in 3D. Tracking a vibrated granular system over six temporal orders of magnitude revealed dynamical heterogeneities, two-step relaxation, and structural memory closely akin to 3D glass formation in supercooled liquids and colloids. These findings illustrate broad prospective utility of MRPT in advancing the exploration, theory, and numerical models of granular matter.
Soft Condensed Matter (cond-mat.soft)
14 pages, 4 figures
Plasmon-Induced Tuning of Cerium Oxidation States in Au@CeO$_x$ Core@Shell Nanoparticles
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-03-31 20:00 EDT
Klára Beranová (1), Kevin C. Prince (2), (3), Mariana Klementová (1), Marek Vronka (1), Oleksandr Romanyuk (1) ((1) FZU - Institute of Physics, Czech Academy of Sciences, Czech, (2) Elettra-Sincrotrone Trieste S. C. p. A., Italy, (3) Charles University, Faculty of Mathematics and Physics, Department of Surface and Plasma Science, Czech)
CeO$_x$-based nanoforms are widely used in catalysis, or biomedical applications due to their redox activity and oxygen storage capacity. The key parameters determining their surface chemistry are the Ce$^{3+}$/Ce$^{4+}$ ratio and the ability to transition between Ce$^{4+}$ and Ce$^{3+}$ states. We synthesized Au@CeO$_x$ core@shell nanoparticles with different thicknesses of CeO$_x$ shells and different Ce$^{3+}$/Ce$^{4+}$ ratios through a photothermal reaction driven by localized surface plasmon resonances (LSPRs) at the Au nanoparticle surface induced by visible light. We introduce a way to further enhance the Ce$^{3+}$/Ce$^{4+}$ ratio in the shell by exposing the Au@CeO$_x$ nanoparticles to visible light using a green laser (532 nm, 50 mW). Our findings based on photoelectron spectroscopy indicate that the Ce$^{4+}$-to-Ce$^{3+}$ transition results from LSPR-induced superheating of the Au@CeO$_x$ interface, leading to the formation of oxygen vacancies and reduction of Ce$^{4+}$ ions. This process is reversible upon air exposure suggesting that the ability to transition between the Ce$^{4+}$ and Ce$^{3+}$ states is retained in the Au@CeO$_x$ nanoparticles. Our study presents the CeO$_x$-based nanoforms with a tunable cerium valence state ratio, highlighting the potential of plasmonic control in optimizing their photocatalytic and enzyme-mimetic properties.
Materials Science (cond-mat.mtrl-sci)
16 pages including the Main text and the Supplementary Material, 7 Figures, submitted to Applied Physics Letters
Spontaneous symmetry breaking with type-B Goldstone modes in the SO($2s+1$) ferromagnetic model: an entanglement perspective
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-03-31 20:00 EDT
Qian-Qian Shi, Huan-Qiang Zhou, Murray T. Batchelor, Ian P. McCulloch
Spontaneous symmetry breaking with type-B Goldstone modes is investigated in the SO($2s+1$) ferromagnetic model. A set of orthonormal basis states in the ground state subspace are constructed, which admit an exact Schmidt decomposition, exposing self-similarities in real space of an abstract fractal underlying the ground state subspace. Focusing on the SO(5) and the SO(6) ferromagnetic spin chains as illustrative examples, finite system-size scaling analysis of the entanglement entropy for this set of orthonormal basis states confirms that the entanglement entropy scales logarithmically with block size in the thermodynamic limit. The prefactor in front of the logarithm is half the number of type-B Goldstone modes $N_B$, which is identified as the fractal dimension $d_f$ for these orthonormal basis states. For the SO($2s+1$) ferromagnetic model $N_B = d_f =s$ for integer $s$ and $N_B = d_f =s+1/2$ for half-odd-integer $s$.
Strongly Correlated Electrons (cond-mat.str-el)
9 pages, 4 figures
The 2D Materials Roadmap
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-03-31 20:00 EDT
Wencai Ren, Peter Bøggild, Joan Redwing, Kostya Novoselov, Luzhao Sun, Yue Qi, Kaicheng Jia, Zhongfan Liu, Oliver Burton, Jack Alexander-Webber, Stephan Hofmann, Yang Cao, Yu Long, Quan-Hong Yang, Dan Li, Soo Ho Choi, Ki Kang Kim, Young Hee Lee, Mian Li, Qing Huang, Yury Gogotsi, Nicholas Clark, Amy Carl, Roman Gorbachev, Thomas Olsen, Johanna Rosen, Kristian Sommer Thygesen, Dmitri Efetov, Bjarke S. Jessen, Matthew Yankowitz, Julien Barrier, Roshan Krishna Kumar, Frank HL Koppens, Hui Deng, Xiaoqin Li, Siyuan Dai, D.N. Basov, Xinran Wang, Saptarshi Das, Xiangfeng Duan, Zhihao Yu, Markus Borsch, Andrea C. Ferrari, Rupert Huber, Mackillo Kira, Fengnian Xia, Xiao Wang, Zhong-Shuai Wu, Xinliang Feng, Patrice Simon, Hui-Ming Cheng, Bilu Liu, Yi Xie, Wanqin Jin, Rahul Raveendran Nair, Yan Xu, Ajit Katiyar, Jong-Hyun Ahn, Igor Aharonovich, Mark C. Hersam, Stephan Roche, Qilin Hua, Guozhen Shen, Tianling Ren, Hao-Bin Zhang, Chong Min Koo, Nikhil Koratkar, Vittorio Pellegrini, Robert J Young, Bill Qu, Max Lemme, Andrew J. Pollard
Over the past two decades, 2D materials have rapidly evolved into a diverse and expanding family of material platforms. Many members of this materials class have demonstrated their potential to deliver transformative impact on fundamental research and technological applications across different fields. In this roadmap, we provide an overview of the key aspects of 2D material research and development, spanning synthesis, properties and commercial applications. We specifically present roadmaps for high impact 2D materials, including graphene and its derivatives, transition metal dichalcogenides, MXenes as well as their heterostructures and moiré systems. The discussions are organized into thematic sections covering emerging research areas (e.g., twisted electronics, moiré nano-optoelectronics, polaritronics, quantum photonics, and neuromorphic computing), breakthrough applications in key technologies (e.g., 2D transistors, energy storage, electrocatalysis, filtration and separation, thermal management, flexible electronics, sensing, electromagnetic interference shielding, and composites) and other important topics (computational discovery of novel materials, commercialization and standardization). This roadmap focuses on the current research landscape, future challenges and scientific and technological advances required to address, with the intent to provide useful references for promoting the development of 2D materials.
Materials Science (cond-mat.mtrl-sci), Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Computational Physics (physics.comp-ph)
104 pages, to be published in 2D Materials
Enhanced superconductivity in LaRu3Si2 by chemical pressure tuning of kagome flat bands
New Submission | Superconductivity (cond-mat.supr-con) | 2025-03-31 20:00 EDT
Ryo Misawa, Markus Kriener, Rinsuke Yamada, Ryota Nakano, Milena Jovanovic, Leslie M. Schoop, Max Hirschberger
In kagome metals, flat bands induced by frustrated hopping serve as a platform for strong electronic correlation, while often exhibiting substantial dispersion along the $k_z$ direction due to interlayer coupling. Here, we investigate the superconductivity of the kagome metal LaRu$3$(Si${1-x}$Ge$_x$)$_2$ by chemical pressure tuning while preserving the Ru-$4d$ states that constitute the kagome flat bands. We observe a sizable enhancement in the density of states up to $x = 0.07$, as determined by the specific heat, with a concomitant increase in the superconducting transition temperature. As supported by our first-principles calculations, the lattice expansion along the $c$-axis by chemical pressure mitigates a detrimental effect of hybridization between kagome layers, thereby reinforcing the three-dimensional localization of flat-band electrons. Providing evidence for LaRu$_3$Si$_2$ as a flat-band hosting superconductor, we demonstrate a simple, yet effective, route to engineer flat bands by uniaxial lattice expansion.
Superconductivity (cond-mat.supr-con), Materials Science (cond-mat.mtrl-sci), Strongly Correlated Electrons (cond-mat.str-el)
18 pages, 3 figures, 3 supplemental figures
Charge creation via quantum tunneling in one-dimensional Mott insulators: A numerical study of the extended Hubbard model
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-03-31 20:00 EDT
Thomas Hansen, Lars Bojer Madsen, Yuta Murakami
Charge creation via quantum tunneling, i.e. dielectric breakdown, is one of the most fundamental and significant phenomena arising from strong light(field)-matter coupling. In this work, we conduct a systematic numerical analysis of quantum tunneling in one-dimensional Mott insulators described by the extended ($U$-$V$) Hubbard model. We discuss the applicability of the analytical formula for doublon-holon (DH) pair production, previously derived for the one-dimensional Hubbard model, which highlights the relationship between the tunneling threshold, the charge gap, and the correlation length. We test the formulas ability to predict both DH pair production and energy increase rate. Using tensor-network-based approaches, we demonstrate that the formula provides accurate predictions in the absence of excitonic states facilitated by the nearest-neighbor interaction $V$. However, when excitonic states emerge, the formula more accurately describes the rate of energy increase than the DH pair creation rate and in both cases gets improved by incorporating the exciton energy as the effective gap.
Strongly Correlated Electrons (cond-mat.str-el), Optics (physics.optics)
14 pages including bibliography and the appendix (11 pages without them), 8 figures in the main text and 1 in the appendix for a total of 9 figures, and 2 tables in the main text
Magnon-mediated terahertz spin transport in metallic Gd|Pt stacks
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-03-31 20:00 EDT
Oliver Gueckstock, Tim Amrhein, Beatrice Andres, Pilar Jiménez-Cavero, Cornelius Gahl, Tom S. Seifert, Reza Rouzegar, Ilie Radu, Irene Lucas, Marko Wietstruk, Luis Morellón, Martin Weinelt, Tobias Kampfrath, Nele Thielemann-Kühn
We study femtosecond spin transport in a Gd|Pt stack induced by a laser pulse. Remarkably, the dynamics of the spin current from Gd to Pt suggests that its dominant driving force is the ultrafast spin Seebeck effect. As the contribution of a transient spin voltage in the metal Gd is minor, Gd acts akin a magnetic insulator here. This view is supported by time- and spin-resolved photoemission, which indicates that a buildup of spin voltage is suppressed by exchange scattering, leading to similar amplitudes and relaxation rates of hot majority- and minority-spin electron populations.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Nanomolding single-crystalline CoIn3 and RhIn3 nanowires
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-03-31 20:00 EDT
Nghiep Khoan Duong, Christian D. Multunas, Thomas Whoriskey, Mehrdad T. Kiani, Shanta R. Saha, Quynh P. Sam, Han Wang, Satya Kushwaha, Johnpierre Paglione, Ravishankar Sundararaman, Judy J. Cha
Intermetallic compounds containing transition metals and group III-V metals tend to possess strong correlations and high catalytic activities, both of which can be enhanced via reduced dimensionality. Nanostructuring is an effective approach to explore this possibility, yet the synthesis of nanostructured intermetallics is challenging due to vast differences in melting points and vapor pressures of the constituent elements. In this work, we demonstrate that this challenge can be overcome with thermomechanical nanomolding (TMNM), exemplified by the synthesis of intermetallic CoIn3 and RhIn3 nanowires. We show that TMNM successfully extrudes single-crystalline nanowires of these compounds down to the 20 nm diameter range, and the nanowires remain metallic with resistivity values higher than calculated bulk resistivity. We discuss possible effects of surface roughness scattering, vacancy-induced scattering, and surface oxidation, on the measured resistivities of the nanowires. For CoIn3 nanowires, the measured resistivity values are the first reported values for this compound.
Materials Science (cond-mat.mtrl-sci), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Cracking Down on Fracture to Functionalise Damage
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-03-31 20:00 EDT
Leo de Waal, Matthaios Chouzouris, Marcelo A. Dias
In this work we propose a novel relationship between topology and damage propagation in Maxwell lattices that redefines fracture as a functional design feature rather than mere degradation. We demonstrate that topologically protected modes, inherently robust against perturbations, localise along lattice discontinuities and govern the mechanical response. By precisely engineering the microstructure, we direct these modes to control stress distributions and trigger predictable, controlled damage. Our findings – validated through comprehensive numerical simulations and experiments – advance our understanding of nontrivial mechanical responses in Maxwell lattices and establish a clear framework for designing materials with improved fracture energy. This work paves the way for further exploration of topology-driven phenomena in mechanical systems and promises a new direction in the design of robust materials.
Soft Condensed Matter (cond-mat.soft), Materials Science (cond-mat.mtrl-sci), Other Condensed Matter (cond-mat.other), Applied Physics (physics.app-ph)
arXiv admin note: text overlap with arXiv:2410.17100
Single-laser pulse toggle switching in CoHo and CoDy single layer alloys : when domain wall motion matters
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-03-31 20:00 EDT
B. Kunyangyuen, G. Malinowski, D. Lacour, J.-X. Lin, Y. Le Guen, L. D. Buda-Prejbeanu, S. Mangin, J. Gorchon, J. Hohlfeld, M. Hehn
Single pulse All Optical Helicity-Independent Toggle Switching is observed in CoHo and CoDy alloys single layers. An original reversal mechanism is reported which contrasts with those observed to date. It is shown that the reversal process is on the {\mu}s timescale involving the reorganization / coalescence of domains and domain walls. The toggle switching is explained considering the unbalanced magnetization distribution stabilized after the ultrashort laser pulse.
Materials Science (cond-mat.mtrl-sci), Applied Physics (physics.app-ph), Optics (physics.optics)
12 pages, 5 figures
Transforming Siliconization into Slippery Liquid-like Coatings
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-03-31 20:00 EDT
Hernán Barrio-Zhang (1), Glen McHale (1), Gary G. Wells (1), Rodrigo Ledesma-Aguilar (1), Rui Han (2), Nicholas Jakubovics (3), Jinju Chen (2) ((1) Institute for Multiscale Thermofluids, School of Engineering, University of Edinburgh, (2) Department of Materials, Loughborough University, (3) School of Dental Sciences, Faculty of Medical Sciences, Newcastle University)
Siliconization is widely used as a coating technique to engineer surface properties, such as in the pharmaceutical and medical device industries to lubricate motion, ensure complete dispensation of product, and to inhibit protein adsorption and biofilm growth. In the hitherto unconnected literature, there has recently been significant progress in understanding the concept of surfaces slippery to liquids. Whereas in the siliconization industry the wettability of surfaces focuses on the hydrophobicity, as measured by contact angle and surface energy, for surfaces slippery to liquids the focus is on the contact angle hysteresis (droplet-on-solid static friction). Moreover, it has been discovered that surfaces with similar static wetting properties can have dramatically different droplet kinetic friction. Here, we report a simple-to-apply coating method to create ultra-low contact angle hysteresis liquid-like coatings for glass (G), polydimethylsiloxane (PDMS), polyurethane (PU), and stainless steel (SS); materials that are used for pharmaceutical/parenteral packaging and medical equipment. Moreover, we demonstrate that the coating’s slow sliding dynamics surface properties for water droplets, which indicate high droplet kinetic friction, can be converted into fast sliding dynamics, which indicate low droplet kinetic friction, by a simple molecular capping (methylation) process. Our results provide new insight into key aspects of siliconization coatings in the context of industrial/commercial processes.
Soft Condensed Matter (cond-mat.soft), Applied Physics (physics.app-ph)
28 pages, 8 Figures, journal pre-print
Nanoparticle Deposition Techniques for Silica Nanoparticles: Synthesis, Electrophoretic Deposition, and Optimization- A review
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-03-31 20:00 EDT
Srabani Karmakar, Milind Deo, Imteaz Rahaman, Swomitra Kumar Mohanty
Silica nanoparticles have emerged as key building blocks for advanced applications in electronics, catalysis, energy storage, biomedicine, and environmental science. In this review, we focus on recent developments in both the synthesis and deposition of these nanoparticles, emphasizing the widely used Stöber method and the versatile technique of electrophoretic deposition (EPD). The Stöber method is celebrated for its simplicity and reliability, offering precise control over particle size, morphology, and surface properties to produce uniform, monodisperse silica nanoparticles that meet high-quality standards for advanced applications. EPD, on the other hand, is a cost-effective, room-temperature process that enables uniform coatings on substrates with complex geometries. When compared to traditional techniques such as chemical vapor deposition, atomic layer deposition, and spin coating, EPD stands out due to its scalability, enhanced material compatibility, and ease of processing. Moreover, Future research should integrate AI-driven optimization with active learning to enhance electrophoretic deposition (EPD) of silica nanoparticles, leveraging predictive modeling and real-time adjustments for improved film quality and process efficiency. This approach promises to accelerate material discovery and enable scalable nanofabrication of advanced functional films.
Materials Science (cond-mat.mtrl-sci)
43 pages, 11 figures
Pressure-temperature phase diagram calculations using polynomial machine learning potentials: A comprehensive study based on global structure prediction and self-consistent phonon calculations
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-03-31 20:00 EDT
Hayato Wakai, Atsuto Seko, Isao Tanaka
Polynomial machine learning potentials (MLPs) based on polynomial rotational invariants have been systematically developed for various systems and applied to efficiently predict crystal structures. In this study, we propose a robust methodology founded on polynomial MLPs to comprehensively enumerate crystal structures under high-pressure conditions and to evaluate their phase stability at finite temperatures. The proposed approach involves constructing polynomial MLPs with high predictive accuracy across a broad range of pressures, conducting reliable global structure searches, and performing exhaustive self-consistent phonon calculations. We demonstrate the effectiveness of this approach by examining elemental silicon at pressures up to 100 GPa and temperatures up to 1000 K, revealing stable phases across these conditions. The framework established in this study offers a powerful strategy for predicting crystal structures and phase stability under high-pressure and finite-temperature conditions.
Materials Science (cond-mat.mtrl-sci), Computational Physics (physics.comp-ph)
REVTeX 4-2, 18 pages, 16 figures
Analog Computing with Heat: Matrix-vector Multiplication with Inverse-designed Metastructures
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-03-31 20:00 EDT
The growing computational demand has spurred interest in energy-efficient frameworks such as neuromorphic and analog computing. A core building block of modern applications is matrix-vector multiplication (MVM), which underpins a wide range of algorithms in both signal processing and machine learning. In this work, we propose performing MVM using inverse-designed metastructures, with heat serving as the signal carrier. The proposed approach is based on a generalization of effective thermal conductivity to systems with multiple input and output ports: The input signal is encoded as a set of applied temperatures, while the output is represented by the power collected at designated terminals. The metastructures are designed using density-based topology optimization, enabled by a differentiable thermal transport solver and automatic differentiation. We apply our methodology to optimize structures that approximate MVM for matrices of various dimensions, achieving 95.9% accuracy for a 3$\times$3 matrix. These results highlight the potential of leveraging heat conduction for analog computing, with applications in scenarios where temperature gradients naturally occur, such as in electronic device hotspots, thermal mapping, and electronic skin.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Materials Science (cond-mat.mtrl-sci)
Comment on “Solvent-Induced Negative Energetic Elasticity in a Lattice Polymer Chain’’
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-03-31 20:00 EDT
In a recent Letter, Shirai and Sakumichi [Phys. Rev. Lett. 130, 148101 (2023), arXiv:2202.12483] presented a study focusing on the origin of a temperature-dependent negative contribution $G_U(T)$ to the elastic modulus $G(T)$ of hydrogels [Yoshikawa et al., Phys. Rev. X 11, 011045 (2021)]. The authors support their findings through an energy-related stiffness $k_U(r,T)$ obtained from a single chain, with $r$ being the end-to-end distance of a random walk on a 3D lattice. It is argued that the parameter $\varepsilon$ related to polymer-solvent interactions is positive, so the energy $E_s$ of an elongated state should be smaller than the energy $E_b$ of a more compact state. We believe that the analogy between $G_U(T)$ and $k_U(r,T)$ might have misled their claim that $G_U(T)<0$ when $\varepsilon>0$.
Soft Condensed Matter (cond-mat.soft), Materials Science (cond-mat.mtrl-sci), Statistical Mechanics (cond-mat.stat-mech)
Comment on arXiv:2202.12483, Shirai and Sakumichi [Phys. Rev. Lett. 130, 148101 (2023), DOI: https://doi.org/10.1103/PhysRevLett.130.148101], 1 page, 1 figure, correspondence with PRL’s editor (5 pages)
Giant Spin Pumping at Polymer/Ferromagnet Interfaces for Hybrid Spintronic Devices
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-03-31 20:00 EDT
Shiva Gaur, Akash Kumar, Himanshu Bangar, Utkarsh Shashank, Hukum Singh, Saroj P. Dash, Anubhav Raghav, Johan Åkerman
While the growing utilization of polymers in flexible electronic devices has sparked significant interest in polymer/metal interfaces, spintronic studies of such interfaces remain limited. Here, we systematically study spin pumping across a polymer/ferromagnet metal interface between hydrogen silsesquioxane (HSQ) oligomer layers ($t_\mathit{HSQ} = 30, 36, 48$ nm) and NiFe ($t_\mathit{NiFe} = 4, 5, 7, 10$ nm) thin films. Using ferromagnetic resonance measurements, we observe strong spin pumping (large linewidth broadening) and a giant spin mixing conductance, reaching 19.8${\rm nm^{-2}}$ for HSQ = 48 nm, \emph{i.e.}comparable to that of heavy metals. Our results suggest efficient spin transfer across the HSQ/NiFe interface, possibly originating from a combination of spin and orbital pumping, and provide valuable insights for designing self-powered and flexible spintronic devices utilizing polymers in combination with ferromagnetic materials.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
15 pages
Revealing the loss mechanisms of a 3D superconducting microwave cavity for use in a dark matter search
New Submission | Superconductivity (cond-mat.supr-con) | 2025-03-31 20:00 EDT
J. C. Esmenda (1), E. A. Laird (1), I. Bailey (1), T. Gamble (2), P. Smith (2), E. Daw (2), Y. A. Pashkin (1) ((1) Department of Physics, Lancaster University, UK, (2) School of Mathematical and Physical Sciences, University of Sheffield, UK)
Superconducting microwave cavities have found applications in many areas including quantum computing, particle accelerators, and dark matter searches. Their extremely high quality factors translate to very narrow bandwidth, which makes them key components of sensitive detectors. In this study, we aim to understand the loss mechanisms of an aluminium cavity and how they change as the cavity material transitions from the superconducting to normal state. We found that at temperatures not much lower than the transition temperature $T_c$, losses are dominated by quasiparticle excitations and are well described by the BCS theory. The exponential decrease of the quasiparticle density below $T_c$ results in a 1000-fold increase of the quality factor, as well as a shift of the resonance frequency due to the change of the kinetic inductance of the superconductor. At very low temperatures, losses due to two-level systems begin to dominate giving a peak in the quality factor of about 27.6 million at 130 mK. Understanding the loss mechanisms is invaluable, as the working temperature of the cavity may vary during operation regardless of its application.
Superconductivity (cond-mat.supr-con)