CMP Journal 2025-07-21
Statistics
Nature Materials: 1
Nature Reviews Physics: 1
arXiv: 49
Nature Materials
Pure-blue single-layer organic light-emitting diodes based on trap-free hyperfluorescence
Original Paper | Electronics, photonics and device physics | 2025-07-20 20:00 EDT
Oskar Sachnik, Naomi Kinaret, Rishabh Saxena, Marvin Manz, Wenlan Liu, Jacob T. Blaskovits, Denis Andrienko, Jasper J. Michels, Paul W. M. Blom, Gert-Jan. A. H. Wetzelaer
Blue organic light-emitting diodes based on thermally activated delayed fluorescence suffer from low stability and broad emission. Hyperfluorescence–in which the excited state created on the thermally activated delayed fluorescence emitter is transferred to a fluorescent terminal emitter with a narrow emission spectrum–is promising towards improving colour purity and stability. However, direct charge trapping on the smaller-gap terminal emitter may lead to direct emissive losses, inhibited charge transport and charge imbalance. Here we demonstrate single-layer pure-blue hyperfluorescent organic light-emitting diodes that are not compromised by charge trapping on the terminal emitter. We reveal that the energetic disorder of the thermally activated delayed fluorescence sensitizer allows for the presence of a terminal emitter with a smaller energy gap, without affecting charge transport. Consequently, the stability benefits of single-layer organic light-emitting diodes can be combined with trap-free hyperfluorescence, resulting in pure-blue emission, a simple device structure, high quantum and power efficiencies, and state-of-the-art operational stability.
Electronics, photonics and device physics, Organic LEDs
Nature Reviews Physics
Atomistic computing of the solid-fluid surface free energy and tension
Review Paper | Chemical physics | 2025-07-20 20:00 EDT
Aziz Ghoufi
This Review surveys methods that use atomistic simulations to compute solid-fluid surface tension, a key parameter for understanding and controlling physical properties at interfaces. Accurate calculation and understanding of these properties are increasingly important in applications, especially in confined-fluid systems in which surface effects dominate over bulk properties. Traditional approaches such as contact angle measurements, the Wilhelmy plate method, and sessile drop methods often fall short in directly measuring solid-liquid surface tension. By contrast, molecular simulations allow the direct extraction of this parameter, offering a more detailed insight into its behaviour at the nanoscale. The Review emphasizes the challenges associated with solid-fluid interfaces, particularly their anisotropic nature, and discusses computational techniques such as the cleaving method, perturbation approaches and capillary wave theory.
Chemical physics, Surfaces, interfaces and thin films
arXiv
Information-Assisted Carnot Engine Surpasses Standard Thermodynamic Bounds
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-07-21 20:00 EDT
Yang Xiao, Qian Zeng, Jin Wang
Information can improve heat engine performance, but the underlying principles are still not so clear. Here we introduce a Carnot information machine (CIE) and obtain a quantitative relationship between the engine performance and information. We demonstrate that the presence of information changes allows the CIE to operate as a heat engine in the regime where the standard Carnot cycle is prohibited, ensures that the efficiency of the CIE is greater than or equal to the standard Carnot efficiency, and significantly enables it to achieve 100% efficiency with positive work extraction for arbitrary two-level systems. We explicitly demonstrate these features using a spin-1/2 system and propose an experimental implementation scheme based on a trapped $ ^{40}\mathrm{Ca}^+$ ion.
Statistical Mechanics (cond-mat.stat-mech), Data Analysis, Statistics and Probability (physics.data-an), Quantum Physics (quant-ph)
The Hofstadter Butterfly: Bridging Condensed Matter, Topology, and Number Theory
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-07-21 20:00 EDT
Celebrating its golden jubilee, the Hofstadter butterfly fractal emerges as a remarkable fusion of art and science. This iconic X shaped fractal captivates physicists, mathematicians, and enthusiasts alike by elegantly illustrating the energy spectrum of electrons within a two dimensional crystal lattice influenced by a magnetic field. Enriched with integers of topological origin that serve as quanta of Hall conductivity, this quantum fractal and its variations have become paradigm models for topological insulators, novel states of matter in 21st century physics. This paper delves into the theoretical framework underlying butterfly fractality through the lenses of geometry and number theory. Within this poetic mathematics, we witness a rare form of quantum magic: Natures use of abstract fractals in crafting the butterfly graph itself. In its simplest form, the butterfly graph tessellates a two dimensional plane with trapezoids and triangles, where the quanta of Hall conductivity are embedded in the integer sloped diagonals of the trapezoids. The theoretical framework is succinctly expressed through unimodular matrices with integer coefficients, bringing to life abstract constructs such as the Farey tree, the Apollonian gaskets, and the Pythagorean triplet tree.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Chaotic Dynamics (nlin.CD)
Generalized cluster algorithms for Potts lattice gauge theory
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-07-21 20:00 EDT
Anthony E. Pizzimenti, Paul Duncan, Benjamin Schweinhart
Monte Carlo algorithms, like the Swendsen-Wang and invaded-cluster, sample the Ising and Potts models asymptotically faster than single-spin Glauber dynamics do. Here, we generalize both algorithms to sample Potts lattice gauge theory by way of a $ 2$ -dimensional cellular representation called the plaquette random-cluster model. The invaded-cluster algorithm targets Potts lattice gauge theory at criticality by implementing a stopping condition defined in terms of homological percolation, the emergence of spanning surfaces on the torus. Simulations for $ \mathbb Z_2$ and $ \mathbb Z_3$ lattice gauge theories on the cubical $ 4$ -dimensional torus indicate that both generalized algorithms exhibit much faster autocorrelation decay than single-spin dynamics and allow for efficient sampling on $ 4$ -dimensional tori of linear scale at least $ 40$ .
Statistical Mechanics (cond-mat.stat-mech), Computational Geometry (cs.CG), Mathematical Physics (math-ph), Probability (math.PR)
Lattice-charge coupling in a trilayer nickelate with intertwined density wave order
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-07-21 20:00 EDT
Xun Jia, Yao Shen, Harrison LaBollita, Xinglong Chen, Junjie Zhang, Yu Li, Hengdi Zhao, Mercouri G. Kanatzidis, Matthew Krogstad, Hong Zheng, Ayman Said, Ahmet Alatas, Stephan Rosenkranz, Daniel Phelan, Mark P. M. Dean, M. R. Norman, J. F. Mitchell, Antia S. Botana, Yue Cao
Intertwined charge and spin correlations are ubiquitous in a wide range of transition metal oxides and are often perceived as intimately related to unconventional superconductivity. Theoretically envisioned as driven by strong electronic correlations, the intertwined order is usually found to be strongly coupled to the lattice as signaled by pronounced phonon softening. Recently, both charge/spin density waves (CDW/SDW) and superconductivity have been discovered in several Ruddlesden-Popper (RP) nickelates, in particular trilayer nickelates RE4Ni3O10 (RE=Pr, La). The nature of the intertwined order and the role of lattice-charge coupling are at the heart of the debate about these materials. Using inelastic X-ray scattering, we mapped the phonon dispersions in RE4Ni3O10 and found no evidence of phonon softening near the CDW wavevector over a wide temperature range. Calculations of the electronic susceptibility revealed a peak at the observed SDW ordering vector but not at the CDW wavevector. The absence of phonon softening is in sharp contrast to that in canonical oxide materials, notably cuprates. Our experimental and theoretical findings highlight the crucial role of the spin degree of freedom and establish a foundation for understanding the interplay between superconductivity and density-wave transitions in RP nickelate superconductors and beyond.
Strongly Correlated Electrons (cond-mat.str-el), Superconductivity (cond-mat.supr-con)
High-performance amorphous superconducting rhenium films by e-beam evaporation
New Submission | Superconductivity (cond-mat.supr-con) | 2025-07-21 20:00 EDT
E.V. Tarkaeva, V.A. Ievleva, A.R. Prishchepa, E.S. Zhukova, A.V. Terentiev, A.Yu. Kuntsevich
We present electron beam evaporation of rhenium films on room-temperature substrates. The films are shown to be amorphous and achieve a record-high critical temperature for rhenium - exceeding 7 K at the midpoint of the transition - alongside a high critical current density of 5000 A/mm^2 and critical fields above 10 T. Terahertz spectroscopy reveals a BCS-like character of superconductivity with a zero-temperature energy gap of approximately 2 meV and subgap optical conductivity. Despite being friable, the films are stable and compatible with lift-off processes that opens the capabilities for superconducting device applications.
Superconductivity (cond-mat.supr-con), Disordered Systems and Neural Networks (cond-mat.dis-nn)
Cutting soft materials: how material differences shape the response
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-07-21 20:00 EDT
Miguel Angel Moreno-Mateos, Paul Steinmann
Cutting soft materials is a complex process governed by the interplay of bulk large deformation, interfacial soft fracture, and contact forces with the cutting tool. Existing experimental characterizations and numerical models often fail to capture the variety of observed cutting behaviors, especially the transition from indentation to cutting and the roles of dissipative mechanisms. Here, we combine novel experimental cutting tests on three representative materials-a soft hydrogel, elastomer, and food-based materials-with a coupled computational model that integrates soft fracture, adhesion, and frictional interactions. Our experiments reveal material-dependent cutting behaviors, with abrupt or smooth transitions from indentation to crack initiation, followed by distinct steady cutting regimes. The computational model captures these behaviors and shows that adhesion and viscous cohesive forces dominate tangential stresses, while Coulomb friction plays a negligible role due to low contact pressures. Together, these results provide new mechanistic insights into the physics of soft cutting and offer a unified framework to guide the design of soft materials, cutting tools, and cutting protocols, with direct relevance to surgical applications and the engineering of food textures optimized for mastication.
Soft Condensed Matter (cond-mat.soft), Classical Physics (physics.class-ph)
Competing Length Scales and Symmetry Frustration Govern Non-Universal Melting in 2D Core-softened Colloidal Crystals
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-07-21 20:00 EDT
Thiago Puccinelli, Alexandre V. Ilha, José Rafael Bordin
We investigate the melting behavior of two-dimensional colloidal crystals stabilized by a core-softened potential featuring two competing interaction length scales. Using molecular dynamics simulations, we analyze three polymorphic solid phases – low-density triangular, stripe, and kagome – and uncover distinct melting pathways. The triangular and kagome crystals undergo abrupt first-order transitions, driven by the interplay between energetic frustration and structural reorganization. In particular, the LDT phase melts through a sharp transition induced by a crossover between the two characteristic length scales. In contrast, the stripe phase exhibits a continuous transition with liquid-crystalline features: orientational and translational order decay gradually, while intra-stripe mobility persists, consistent with a KTHNY-like scenario. These findings demonstrate that melting in 2D soft-matter systems is inherently non-universal and governed by the competition between lattice symmetry, frustration, and multiple interaction scales. Our results provide microscopic insight into melting mechanisms beyond classical universality classes and offer guiding principles for the design of self-assembled materials with tunable phase behavior.
Soft Condensed Matter (cond-mat.soft), Chemical Physics (physics.chem-ph)
Magnon-induced topological phases
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-07-21 20:00 EDT
Kosuke Fujiwara, Takahiro Morimoto
Topological electronic states such as topological insulators and quantum Hall states typically require strong spin-orbit coupling or magnetic fields. In this study, we consider an electron system coupled to a spin system, where electrons interact with magnons, quasiparticles of spin waves. We show that the interaction between electrons and magnons transfers the effect of symmetry breaking in the spin system to the electron system, whereby a non-trivial topological phase can be induced in the electron system that is otherwise topologically trivial. Through this ``topology transfer’’ mechanism, we demonstrate the realization of various topological phases, including quantum Hall and quantum spin Hall insulators, in simple ferromagnetic spin systems, without requiring strong spin-orbit coupling or magnetic field for electron systems.
Strongly Correlated Electrons (cond-mat.str-el)
15 pages, 12 figures
Optically detected magnetic resonance of nitrogen-vacancy centers in microdiamonds inside nanopolycrystalline diamond anvil cell
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-21 20:00 EDT
Masahiro Ohkuma, Keigo Arai, Kenji Ohta, Toru Shinmei, Ryo Matsumoto, Yoshihiko Takano, Tetsuo Irifune
We demonstrated optically detected magnetic resonance (ODMR) of nitrogen-vacancy (NV) centers in microdiamonds inside a diamond anvil cell pressurized with nanopolycrystalline diamond (NPD) anvils. NPD exhibits high optical transparency, superior hardness, and low thermal conductivity, making it suitable for optical and spectroscopic measurements under high-pressure and high-temperature conditions. We observed the ODMR signal from an ensemble of NV centers under high pressures, reaching up to 20 GPa, with a culet diameter of 600 $ \mu$ m. We also performed ODMR measurements on multiple microdiamonds sealed inside a sample chamber and found that the resonance frequency varied with the pressure distribution. The combination of NPD and microdiamonds containing NV centers is auspicious for pressure and magnetic imaging under concurrent high-pressure and high-temperature conditions.
Materials Science (cond-mat.mtrl-sci)
Learning general pair interactions between self-propelled particles
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-07-21 20:00 EDT
Jérôme Hem, Alexis Poncet, Pierre Ronceray, Daiki Nishiguchi, Vincent Démery
Synthetic active matter systems, such as active colloids, often have complex interactions, which can be of hydrodynamic, chemical or electrostatic origin and cannot be computed from first principles. Here, we use Stochastic Force Inference to learn general pair interactions, including transverse forces and torques, between self-propelled Janus particles from experimental trajectories. We use data from two experiments: one where the particles flock, and one where the system remains disordered. The learned interactions are then fed to numerical simulations, which reproduce all the experimental observables and could be extrapolated to different densities. Overall, we find that the radial interaction is mostly repulsive and isotropic, while the angular interaction has a richer angular dependence, which controls the behavior of the system; the transverse interaction is negligible. Finally, testing the symmetry relations obeyed by the inferred interactions allows us to show that they cannot come from electrostatics only, so that they must have a hydrodynamic component.
Soft Condensed Matter (cond-mat.soft), Statistical Mechanics (cond-mat.stat-mech)
Nonlinear management of the miscibility-immiscibility transition in binary Bose-Einstein condensates
New Submission | Quantum Gases (cond-mat.quant-gas) | 2025-07-21 20:00 EDT
B. B. Baizakov, B. A. Malomed, M. Salerno
We investigate application of the nonlinearity management (NM, i.e., periodic variation of the strength of the inter-component repulsion) to the miscibility-immiscibility (MIM) transition across the critical point of a two-component BEC, both with and without the linear mixing (Rabi coupling, RC) between the components. To this end, we first identify, by means of a variational approximation and numerical solution, diverse stationary domain-wall (DW) structures supported by the system in the absence of the management. The approximate analytical solutions for the DWs are found to be in excellent agreement with their numerical counterparts. An analytical estimate is also produced for the upshift of the MIM transition caused by the pressure of the trapping potential in the case of a confined system. An exact DW solution is produced for the system including the Pöschl-Teller potential, which is stable (unstable) if the potential is repulsive (attractive). Further, we find the spectrum of linear excitations in the spatially uniform mixed state, and thus establish parameter regions where the system is stable/unstable against demixing. In particular, RC upshifts the critical strength of the inter-component repulsion for the onset of the MIM transition. Eigenfrequencies of excitations on top of DW states are identified from numerical simulations through monitoring the evolution of perturbed states. Weak NM applied at the DW eigenfrequency reveals features of the nonlinear resonance. Stronger NM, under which the system periodically crosses the MIM-transition point, restricts the miscibility.
Quantum Gases (cond-mat.quant-gas), Pattern Formation and Solitons (nlin.PS)
13 pages, 9 figures. To be published in Phys. Rev. E
Topological Majorana flat bands in the Kitaev model on a Bishamon-kikko lattice
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-07-21 20:00 EDT
We unveil an interesting example of topological flat bands of Majorana fermions in quantum spin liquids. We study the Kitaev model on a periodically depleted honeycomb lattice, under a magnetic field within the perturbation theory. The model can be straightforwardly extended while maintaining the exact solvability, and its ground state is a quantum spin liquid as on the honeycomb lattice. As fractionalized excitations, there are unpaired localized Majorana fermions in addition to the itinerant Majorana fermions and $ \mathbb{Z}_2$ fluxes. We show that in the absence of the magnetic field the Majorana fermions have completely flat bands at zero energy, and by applying the magnetic field, they turn into topological flat bands with nonzero Chern number. By varying the anisotropy of the interactions and the magnitude of the magnetic field, we clarify that the system exhibits a variety of topological phases that do not appear in the original model. We emphasize that the topological flat bands that give this rich topology come from the hybridization of the Majorana flat bands and unpaired Majorana fermions, which is unique to the flat bands of fractionalized excitations in quantum spin liquids. Our findings would stimulate the exploration of a new type of Kitaev materials exhibiting rich topology from topological Majorana flat bands.
Strongly Correlated Electrons (cond-mat.str-el)
14 pages, 10 figures
Topological signatures of jamming in granular force networks via persistent homology
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-07-21 20:00 EDT
Vishali S, Abrar Naseer, Vijay Natarajan, Tejas G Murthy
Granular materials exhibit intricate force networks, often concentrated in chains rather than being uniformly distributed. These meso-scale structures are complex to characterize, owing to their heterogeneous and anisotropic nature. We present a topological analysis in which we characterize force networks by studying the connectivity of contact forces in granular materials. We obtain the force network data during the isotropic compression of a 2D granular ensemble, which comprises of bidisperse photoelastic disks. The force chains are visualized using a bright-field polariscope, which are then analyzed using photoelasticity techniques to get contact force information across all the particles in the granular ensemble. The forces and contact network are studied using topological descriptors. We analyze the evolution of these descriptors using methods developed in the areas of computational topology and persistent homology. Specifically, we evaluate the number of homology class generators to capture critical changes in network connectivity with the evolution of packing fraction. Building on previous applications of persistent homology, our topological analysis of the force network provides valuable insights by distinguishing different phases of particle interactions and revealing unique structural transitions around jamming and thus help enhance our understanding of the stability and jamming dynamics in granular systems.
Soft Condensed Matter (cond-mat.soft)
Accepted for publication in Powders and Grains 2025
Strain-Engineered Electronic Structure and Superconductivity in La$_3$Ni$_2$O$_7$ Thin Films
New Submission | Superconductivity (cond-mat.supr-con) | 2025-07-21 20:00 EDT
Yu-Han Cao, Kai-Yue Jiang, Hong-Yan Lu, Da Wang, Qiang-Hua Wang
Recently, the films of the Ruddlesden-Popper (RP) nickelate superconductors, in which the (La,Pr)$ 3$ Ni$ 2$ O$ 7$ system exhibits a remarkable transition temperature $ T_c$ exceeding 40 K, were synthesized at ambient pressure. We systematically investigate the band structures and electronic correlation effect to identify the key factors controlling superconductivity and pathways to enhance $ T_c$ . Based on density functional theory (DFT) calculations, we construct a bilayer two-orbital ($ 3d{3z^2-r^2}$ and $ 3d{x^2-y^2}$ ) tight-binding model for a series of in-plane compression mimicking the substrate effect. We find the band energy at the $ M$ point drops with the compression, leading to increase of the density of states at the Fermi level, in stark contrast to the behavior of the bulk under pressure. We then apply functional renormalization group (FRG) method to study the electronic correlation effect on the superconductivity. We find the $ s\pm$ -wave pairing symmetry remains robust in the films, the same as the bulk. But somewhat surprisingly, for the films, we find $ T_c$ can be enhanced by reducing the in-plane lattice constant, increasing the out-of-plane lattice constant, or further electron-doping. These findings are consistent with the itinerant picture of the superconductivity induced by spin-fluctuations and provide theoretical support for further boosting $ T_c$ in future experiments.
Superconductivity (cond-mat.supr-con), Strongly Correlated Electrons (cond-mat.str-el)
5 pages, 5 figures
Spin-Electric Control of Individual Molecules on Surfaces
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-07-21 20:00 EDT
Paul Greule, Wantong Huang, Máté Stark, Kwan Ho Au-Yeung, Johannes Schwenk, Jose Reina-Gálvez, Christoph Sürgers, Wolfgang Wernsdorfer, Christoph Wolf, Philip Willke
Individual magnetic molecules are promising building blocks for quantum technologies because of their chemical tunability, nanoscale dimensions, and ability to self-assemble into ordered arrays. However, harnessing their properties in quantum information processing requires precise local control of their spin properties. In this work, we present spin-electric coupling (SEC) for two molecular spin systems, iron phthalocyanine (FePc) and Fe-FePc complexes, adsorbed on a surface. We use electron spin resonance combined with scanning tunnelling microscopy (ESR-STM) to locally address them with the STM tip and electrically tune them using the applied bias voltage. These measurements reveal a pronounced nonlinear voltage dependence of the resonance frequency, linked to the energic onset of other molecular orbitals. We attribute this effect to a transport-mediated exchange field from the magnetic tip, providing a large, highly localized, and broadly applicable SEC mechanism. Finally, we demonstrate that the SEC enables all-electrical coherent spin control: In Rabi oscillation measurements of both single and coupled Fe-FePc complexes we show that the spin dynamics can be tuned, demonstrating a pathway towards electrically controlled quantum operation.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Quantum Physics (quant-ph)
18 pages, 4 figures
Moiré-Induced Magnetoelectricity in Twisted Bilayer NiI2
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-21 20:00 EDT
Haiyan Zhua, Hongyu Yua, Weiqin Zhua, Guoliang Yua, Changsong Xu, Hongjun Xiang
Twisted magnetic van der Waals (vdW) materials offer a promising route for multiferroic engineering, yet modeling large-scale moiré superlattices remains challenging. Leveraging a newly developed SpinGNN++ framework that effectively handles spin-lattice coupled systems, we develop a comprehensive interatomic machine learning (ML) potential and apply it to twisted bilayer NiI2 (TBN). Structural relaxation introduces moiré-periodic “bumps” that modulate the interlayer spacing by about 0.55Å and in-plane ionic shifts up to 0.48Å. Concurrently, our ML potential, which faithfully captures all key spin interactions, produces reliable magnetic configurations; combined with the generalized KNB mechanism, it yields accurate spin-driven polarization. For twist angles 1.89^{\circ} \leq \theta \leq 2.45^{\circ}, both mechanisms become prominent, yielding rich polarization textures that combine ionic out-of-plane dipoles with purely electronic in-plane domains. In the rigid (unrelaxed) bilayer, skyrmions are absent; lattice relaxation is essential for generating polar-magnetic topologies. In contrast, near {\theta} \approx 60^{\circ}, stacking-dependent ferroelectric displacements dominate, giving rise to polar meron-antimeron networks. These results reveal cooperative ionic and spin-driven ferroelectricity in TBN, positioning twisted vdW magnets as adaptable platforms for tunable multiferroic devices.
Materials Science (cond-mat.mtrl-sci)
Enhancing Coherence with a Clock Transition and Dynamical Decoupling in the Cr$_7$Mn Molecular Nanomagnet
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-07-21 20:00 EDT
Guanchu Chen (1,2), Brendan C. Sheehan (1,2), Ilija Nikolov (1), James W. Logan (1), Charles A. Collett (1), Gajadhar Joshi (1), Grigore A. Timco (3), Jillian E. Denhardt (2), Kevin R. Kittilstved (2), Richard E. P. Winpenny (3), Jonathan R. Friedman (1,2) ((1) Department of Physics and Astronomy, Amherst College, Amherst, USA (2) Department of Physics, University of Massachusetts Amherst, Amherst, USA (3) Department of Chemistry, The University of Manchester, Manchester, UK)
Molecular magnets are attractive as spin qubits due to their chemical tunability, addressability through electron-spin resonance techniques, and long coherence times. Clock transitions (CTs), for which the system is immune to the effect of magnetic-field fluctuations to first order, provide a method to enhance the coherence time $ T_2$ , and to reveal mechanisms of decoherence that are not due to such fluctuations. Here we investigate two variants of Cr$ _7$ Mn, a spin-1 molecular nanomagnet, at fields near a zero-field CT. We find that at temperatures $ \le$ 2 K, $ T_2\sim1$ $ \mu$ s at the CT using a Hahn-echo pulse sequence. Away from the CT, electron-spin-echo envelope modulation (ESEEM) oscillations due to coupling to nuclear spins are observed and have a $ T_2$ as high as $ 1.35$ $ \mu$ s, indicating a distinct mechanism of coherence preservation. Dynamical decoupling with the CPMG pulse sequence yields $ T_2\sim!2.8$ $ \mu$ s at the CT and up to $ \sim!3.6$ $ \mu$ s in the ESEEM regime along with a demodulation of the oscillatory behavior. The experimental values of $ T_2$ are largely independent of the degree of dilution of the molecules in solvent or whether the solvent is deuterated, indicating that much of the decoherence and ESEEM arises from sources within the molecules themselves. To account for decoherence, we develop a model that includes not only field fluctuations but also fluctuations in the CT transition frequency itself. Our results can be well explained by treating the environment as a combination of noise at the nuclear Larmor precession frequency and $ 1/f$ noise in the transverse anisotropy parameter $ E$ . Such information about the microscopic origins of decoherence can aid the rational design of molecular-based spin qubits.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Quantum Physics (quant-ph)
The Main Manuscript has 16 pages and 12 figures. The Supplement has 15 pages and 11 figures
Autferroicity: concept, candidates, and applications
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-21 20:00 EDT
Jun-Jie Zhang, Ziwen Wang, Shuai Dong
Autferroicity is a newly proposed form of hybrid ferroicity, which is a sister branch of multiferroicity. It is characterized by the mutually exclusive magnetic and polar phases within a single system, giving a unique seesaw-type magnetoelectric coupling. This perspective provides a theoretical overview of its underlying concept, phase diagram characteristics, and representative candidates such as Ti-based trichalcogenide monolayers, while also highlighting its potential applications in nonvolatile memory devices and true random number generation.
Materials Science (cond-mat.mtrl-sci)
Phase Transition Under Control: Toward Application-Oriented Luminescence Thermometry and Thermally Activated Emission
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-21 20:00 EDT
M. T. Abbas, M. Szymczak, D. Szymanski, J. Zeler, M. Drozd, L. T. K Giang, L. Marciniak
Phase-transition-based luminescent thermometers are characterized by two inherent limitations: a narrow thermal operating range and the presence of a hysteresis loop in the thermometric parameter. In this work, we demonstrate that controlling the particle size of LaGaO3:Eu3+ phosphors enables significant enhancement of thermometric performance. Specifically, a reduction in grain size dispersion leads to an increase in relative thermal sensitivity and significantly narrows the hysteresis loop. As a result of this approach, the relative sensitivity was increased to 18.2% K-1 for LaGaO3:Eu3+ synthesized via the solid-state method, compared to 3.0% K-1 for the counterpart prepared using the Pechini method. Furthermore, we show that the intentional incorporation of Al3+ and Sc3+ co-dopant ions allows for continuous tuning of the structural phase transition temperature from 165 K for 15% Al3+ to 491 K for 2% Sc3+, without significantly affecting the low-temperature spectroscopic properties of Eu3+ ions. This ability to shift the phase transition temperature in LaGaO3 offers a practical route to modulate the thermal response range of the luminescent thermometer, enabling its adaptation to specific application requirements. The empirical relationship established in this study between the phase transition temperature and the ionic radius mismatch parameter provides a predictive tool for the rational design of phase-transition-based phosphors with tailored thermometric performance. The ability to systematically tune the phase transition temperature via ionic radius mismatch, together with enhanced thermometric performance resulting from reduced grain size dispersion, establishes a coherent strategy for the rational design of high-sensitivity, low-hysteresis thermal sensors.
Materials Science (cond-mat.mtrl-sci)
Investigation of competing magnetic orders and the associated spin-phonon coupling effect in quasi-2D Cr1+xTe2 (x = 0.22) single crystal
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-07-21 20:00 EDT
Gayathri V, Sathishkumar M, Sandip Kumar Kuila, Vikash Kumar, Abhidev B, Reshna Elsa Philip, Partha Pratim Jana, Soham Manni
Single crystals of quasi-2D chromium telluride system represented by Cr1+xTe2 (x = 0.22), which crystallizes in the trigonal structure with the c-axis as the growth direction, are synthesized by the flux method. The magnetization measurements revealed the coexistence and competition between ferromagnetic and antiferromagnetic exchange interactions due to the presence of the intercalated Cr-layers. A series of diverse magnetic transitions is exhibited by the crystal. While cooling the crystal, it undergoes a paramagnetic to antiferromagnetic transition at 190 K, followed by a transition into a ferromagnetic state at around 160 K, and a spin-canting at a lower temperature of 75 K. A possible lack of inversion symmetry in the crystal structure, along with the observance of an unusual jump and loop opening in the isothermal magnetization suggests that the crystals Cr1+xTe2 (x = 0.22) may host skyrmions. Furthermore, concomitant to their magnetic transitions, anomalies were observed in the derived Breit-Wigner-Fano fit parameters obtained from the asymmetric temperature-dependent Raman spectra, evidencing a strong spin-phonon coupling effect, intrinsic to the grown crystals. A strong perpendicular magnetic anisotropy along with the robust spin-phonon coupling, makes the system a promising candidate for prospective spintronics applications.
Strongly Correlated Electrons (cond-mat.str-el), Materials Science (cond-mat.mtrl-sci)
5 pages + Supplimentary material
Resonant two-qubit gates for fermionic simulations with spin qubits
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-07-21 20:00 EDT
Konstantinos Tsoukalas, Alexei Orekhov, Bence Hetényi, Uwe von Lüpke, Jeth Arunseangroj, Inga Seidler, Lisa Sommer, Eoin G. Kelly, Leonardo Massai, Michele Aldeghi, Marta Pita-Vidal, Stephen W. Bedell, Stephan Paredes, Felix J. Schupp, Matthias Mergenthaler, Gian Salis, Andreas Fuhrer, Patrick Harvey-Collard
In gate-defined semiconductor spin qubits, the highly tunable Heisenberg exchange interaction is leveraged to implement fermionic two-qubit gates such as CZ and SWAP. However, the broader family of fermionic simulation (fSim) gates remains unexplored, and has the potential to enhance the performance of near-term quantum simulation algorithms. Here, we demonstrate a method to implement the fSim gate set in spin qubits using a single pulse combining baseband and resonant exchange drives. This approach minimizes gate duration and drive amplitude, mitigating decoherence and crosstalk. We validate its effectiveness by realizing a resonant iSWAP gate between two hole spins in germanium, achieving a fidelity of 93.8(5)% extracted with interleaved randomized benchmarking. Quantum process tomography confirms accurate gate calibration and identifies qubit decoherence as the dominant error source. Our results establish a practical route toward a versatile and efficient two-qubit gate set for spin-based quantum processors.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Quantum Physics (quant-ph)
Molecular Dynamics Study of Rayleigh-Plateau Instability at Liquid-Liquid Interfaces
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-07-21 20:00 EDT
Shunta Kikuchi, Hiroshi Watanabe
We investigated the Rayleigh-Plateau instability at the interface between two immiscible liquids of equal viscosity using molecular dynamics simulations. We examined two types of initial conditions: one involving a single-mode perturbation at the interface and the other without any imposed perturbation. The growth rate under single-mode perturbation showed strong agreement with classical theory, particularly for large cylinder this http URL, for smaller radii, the growth rate deviated significantly from the theoretical prediction. This discrepancy can be attributed to the effects of thermal fluctuations or pressure differences between the inside and outside of a cylinder. In contrast, with initial conditions free of perturbation, we observed a relationship between breakup time and minimum radius, where the power exponent decreased as the radius decreased. This result suggests that thermal fluctuations have a more substantial impact on systems of smaller dimensions. This study demonstrated that imposing single-mode perturbations effectively suppresses thermal noise and mode coupling, thereby yielding growth rates consistent with those predicted by linear stability analysis.
Soft Condensed Matter (cond-mat.soft), Statistical Mechanics (cond-mat.stat-mech)
18 pages, 11 figures
Improving structure search with hyperspatial optimization and TETRIS seeding
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-21 20:00 EDT
Daviti Gochitashvili, Maxwell Meyers, Cindy Wang, Aleksey N. Kolmogorov
Advanced structure prediction methods developed over the past decades include an unorthodox strategy of allowing atoms to displace into extra dimensions. A recently implemented global optimization of structures from hyperspace (GOSH) has shown promise in accelerating the identification of global minima on potential energy surfaces defined by simple interatomic models. In this study, we extend the GOSH formalism to more accurate Behler-Parrinello neural network (NN) potentials, make it compatible with efficient local minimization algorithms, and test its performance on nanoparticles and crystalline solids. For clusters modeled with NN potentials, four-dimensional optimization offers fairly modest improvement in navigating geometric relaxation pathways and incurs increased computational cost largely offsetting the benefit, but it provides a significant advantage in facilitating atom swaps in nanoalloys. In comparison, the introduction of a moderate, controlled bias for generating more physically sensible starting configurations, achieved via TETRIS-inspired packing of atomic blocks, has a more direct impact on the efficiency of global structure searches. The benchmarked systems are Lennard-Jones clusters, Au or Cu-Pd-Ag nanoparticles and binary Sn alloys described by NN potentials, and compounds with covalent B or BC frameworks modeled with density functional theory
Materials Science (cond-mat.mtrl-sci), Computational Physics (physics.comp-ph)
Intraband circular photogalvanic effect in Weyl semimetals
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-07-21 20:00 EDT
We apply the semiclassical theory including the Berry curvature dipole, side jumps and skew scattering for a quantitative description of the circular photogalvanic effect (CPGE) in Weyl semimetals at intraband absorption. In contrast to gapped systems where they completely exhaust all contributions to the CPGE current, all previously known semiclassical mechanisms give a result different from that obtained using a complete quantum-mechanical approach. We show that this difference in the existing quasiclassical and full quantum-mechanical approaches persists at all spatial ranges of the disorder potential. Apparently, the implementation of another microscopic mechanism into the quasiclassical description of the CPGE is required.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Quantum Physics (quant-ph)
5+5 pages, 2 figures
Less is more: removing a single bond increases the toughness of elastic networks
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-07-21 20:00 EDT
Antoine Sanner, Luca Michel, Alessandra Lingua, David S. Kammer
We investigate how the removal of a single bond affects the fracture behavior of triangular spring networks, whereby we systematically vary the position of the removed bond. Our simulations show that removing the bond has two contrasting effects on the fracture energy for initiation of crack propagation and on the fracture energy for failure of the entire network. A single missing bond can either lower or raise the initiation fracture energy, depending on its placement relative to the crack tip. In contrast, the failure fracture energy is always equal to or greater than that of a perfect network. For most initial placements of the missing bond, the crack path remains straight, and the increased failure fracture energy results from arrest at the point of maximum local fracture resistance. When the crack deviates from a straight path, we observe an even higher fracture energy, which we attribute primarily to crack bridging. This additional toughening mechanism becomes active only at low failure strains of the springs; at higher failure strains, the crack path tends to remain straight. Altogether, our results demonstrate that even a single bond removal can significantly enhance toughness, offering fundamental insights into the role of defects in polymer networks and informing the design of tough architected materials.
Soft Condensed Matter (cond-mat.soft), Materials Science (cond-mat.mtrl-sci)
Resonant Photoluminescence of Quantum Incompressible Liquids
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-07-21 20:00 EDT
D. A. Shchigarev, A. V. Larionov, L. V. Kulik, E. M. Budanov, I. V. Kukushkin, V. Umansky
We investigate resonant photoluminescence arising from incompressible quantum liquids formed in two-dimensional electron systems. We demonstrate that, for excitons composed of a photoexcited electron occupying the upper spin sublevel of the zeroth Landau level and a valence-band hole, the influence of disorder potential fluctuations on optical recombination is strongly suppressed, indicating complete screening of the disorder. We identify an optical invariant quantity that is insensitive to excitation energy yet strongly dependent on the electron temperature, serving as a probe of exciton recombination in quantum liquids. Analysis of this quantity reveals that quantum-liquid formation initiates at (n = 1/3) as the electron temperature decreases, consistent with the Laughlin state. Upon further cooling, the range of filling factors exhibiting quantum-liquid behavior expands continuously from (n = 1/3) toward (n = 1/2). Transitions between distinct incompressible quantum-liquid states occur smoothly, without well-defined phase boundaries separating insulating and conducting regimes. Locally, the system retains quantum-liquid characteristics even as bulk transport measurements indicate finite conductivity. Finally, we present a phase diagram delineating the stability region of incompressible quantum liquids relative to conductive phases.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
6 pages, 5 figures
Extension of Second-Principles Density Functional Theory into the time domain
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-21 20:00 EDT
Toraya Fernández-Ruiz, Jorge Íñiguez, Javier Junquera, Pablo García-Fernández
We present an extension of the second-principles density functional theory (SPDFT) method to perform time-dependent simulations. Our approach, which calculates the evolution of the density matrix in real time and real space using the Liouville-von Neumann equation of motion, allows determining optical and transport properties for very large systems, involving tens of thousands of atoms, using very modest computational platforms. In contrast with other methods, we show that SPDFT can be applied to a wide variety of materials including both metals and insulators. In particular, we illustrate its capabilities by obtaining the spectra of SrTiO$ _3$ , diamond and metallic lithium. We find that, while SPDFT results in SrTiO$ _3$ are quite similar to those obtained from DFT using linear perturbation theory, we observe significant improvements over this method in both diamond and metallic lithium. The inclusion of electron-electron interactions during the evolution of the density matrix in diamond allows the spectra to more closely resemble those obtained with the Bethe-Salpeter equation than from perturbation theory. In lithium time-dependent SPDFT not only predicts interband transitions but also the Drude peak, opening the possibility of detailed ab initio studies of transport properties beyond many of the usual approximations.
Materials Science (cond-mat.mtrl-sci), Other Condensed Matter (cond-mat.other)
14 pages, 8 figures
Tuning the Surface States of $Fe_3O_4$ Nanoparticles for Enhanced Magnetic Anisotropy and Induction Efficacy
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-07-21 20:00 EDT
Kyle A. Portwin (1 and 2), Pablo Galaviz (3), Xiaoning Li (1), Chongyan Hao (1), Lachlan A. Smillie (1), Mengyun You (1), Caleb Stamper (1), Richard Mole (3), Dehong Yu (3), Kirrily C. Rule (2 and 3), David L. Cortie (2 and 3), Zhenxiang Cheng (1) ((1) Institute for Superconducting and Electronic Materials, Faculty of Engineering and Information Science, University of Wollongong, North Wollongong, Australia (2) School of Physics, Faculty of Engineering and Information Science, University of Wollongong, Wollongong, Australia (3) Australian Centre for Neutron Scattering, Australian Nuclear Science and Technology Organisation, Lucas Heights, Australia)
Magnetite ($ Fe_3O_4$ ) nanoparticles are crucial for biomedical applications, including magnetic hyperthermia, targeted drug delivery, and MRI contrast enhancement, due to their biocompatibility and unique physicochemical properties. Here, we investigate how surface states influence their induction performance. Heat treatment removes surface water and FeOOH, forming a $ {\gamma}$ -$ Fe_2O_3$ shell, as confirmed by synchrotron powder diffraction, neutron powder diffraction, thermogravimetric analysis, X-ray photoelectron spectroscopy, X-ray absorption spectroscopy, and time-of-flight inelastic neutron spectroscopy. AC magnetic susceptibility measurements reveal that this surface modification enhances magnetic anisotropy and reduces the spin relaxation time, leading to a 140% increase in the specific absorption rate. Additionally, the increased anisotropy suppresses the low-temperature clustered spin-glass transition and raises the blocking temperature. These findings highlight surface-state engineering as a powerful approach to optimizing $ Fe_3O_4$ nanoparticles for biomedical applications.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Sizable superconducting gap and anisotropic chiral topological superconductivity in the Weyl semimetal PtBi$_2$
New Submission | Superconductivity (cond-mat.supr-con) | 2025-07-21 20:00 EDT
Xiaochun Huang, Lingxiao Zhao, Sebastian Schimmel, Julia Besproswanny, Patrick Härtl, Christian Hess, Bernd Büchner, Matthias Bode
Topological superconductors offer a fertile ground for realizing Majorana zero modes – topologically protected, zero-energy quasiparticles that are resilient to local perturbations and hold great promise for fault-tolerant quantum computing. Recent studies have presented encouraging evidence for intrinsic topological superconductivity in the Weyl semimetal trigonal PtBi$ _2$ , hinting at a robust surface phase potentially stable beyond the McMillan limit. However, due to substantial spatial variations in the observed superconducting (SC) gap $ \Delta$ the nature of the underlying order parameter $ \Delta$ ($ k$ ) remained under debate. Here we report the realization of sizable surface SC gaps ($ \Delta > 10,\mathrm{meV}$ ) in PtBi$ _2$ , exhibiting remarkable spatial uniformity from hundreds of nanometers down to the atomic level, as revealed by scanning tunneling microscopy and spectroscopy. Building on this spatial homogeneity – indicative of long-range phase coherence – we uncover previously unobserved low-energy Andreev bound states (ABSs) that ubiquitously emerge within the SC gap across the surface. Theoretical simulations that closely reproduce the experimental spectra, reveal an anisotropic chiral pairing symmetry of $ \Delta$ ($ k$ ), and further suggest that the observed ABSs are of topological origin. The combination of a large, nontrivial pairing gap and accessible surface states establishes PtBi$ _2$ as a compelling platform for investigating topological superconductivity and its associated Majorana modes.
Superconductivity (cond-mat.supr-con), Materials Science (cond-mat.mtrl-sci)
The main manuscript consists of 14 pages and 4 figures, with 6 additional figures in the extended data section
Driven shear flow in biological magneto-active fluids
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-07-21 20:00 EDT
Malo Marmol, Cécile Cottin-Bizonne, Andrejs Cebers, Damien Faivre, Christophe Ybert
Active fluids made of powered suspended particles have unique abilities to self-generate flow and density structures. How such dynamics can be triggered and leveraged by external cues is a key question of both biological and applied relevance. Here we use magnetotactic bacteria to explore how chemotaxis and magnetotaxis – leading, respectively, to positional and orientational responses – combine to generate global scale flows. Such steady regime can be quantitatively captured by a magneto-active hydrodynamic model, while time-dependent magnetic driving unveils additional patterning complexity. Overall, our findings shed light on how active fluids respond to the ubiquitous situation of multiple external information, also suggesting routes for their manipulation.
Soft Condensed Matter (cond-mat.soft)
6 pages, 4 figures. Submitted
Linear response and exact hydrodynamic projections in Lindblad equations with decoupled Bogoliubov hierarchies
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-07-21 20:00 EDT
Patrik Penc, Fabian H. L. Essler
We consider a class of spinless-fermion Lindblad equations that exhibit decoupled BBGKY hierarchies. In the cases where particle number is conserved, their late time behaviour is characterized by diffusive dynamics, leading to an infinite temperature steady state. Some of these models are Yang-Baxter integrable, others are not. The simple structure of the BBGKY hierarchy makes it possible to map the dynamics of Heisenberg-picture operators on few-body imaginary-time Schrödinger equations with non-Hermitian Hamiltonians. We use this formulation to obtain exact hydrodynamic projections of operators quadratic in fermions, and to determine linear response functions in Lindbladian non-equilibrium dynamics.
Statistical Mechanics (cond-mat.stat-mech), Strongly Correlated Electrons (cond-mat.str-el)
23 pages
Exact ground state on the 3D analogue of the Shastry-Sutherland model
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-07-21 20:00 EDT
Kelvin Salou-Smith, Arnaud Ralko, Ludovic D.C. Jaubert
Exact results in frustrated quantum many-body systems are rare, especially in dimensions higher than one. The Shastry-Sutherland (SS) model stands out as a rare example of a two-dimensional spin system with an exactly solvable dimer singlet ground state. In this work, we introduce a three-dimensional analogue of the SS lattice, constructed by deforming the pyrochlore lattice to preserve the local SS geometry. Despite the dimensional increase and altered topology, the ground-state phase diagrams of classical Ising and Heisenberg spins, remain analytically tractable and closely follow their 2D counterparts, including the existence of a 1/3 magnetization plateau and umbrella states. Most notably, for quantum spins S = 1/2, the dimer singlet state survives as an exact ground state over a finite region of the phase diagram. We argue, using exact diagonalization, that the singlet phase is stabilized beyond its 2D counterpart, suggesting enhanced robustness in three dimensions. These results offer a rare, controlled platform to explore the impact of dimensionality on quantum frustration, exact solvability, and potential spin liquid behavior in 3D, with relevance to emergent topological and magnetic phases.
Strongly Correlated Electrons (cond-mat.str-el), Statistical Mechanics (cond-mat.stat-mech)
Predicting temperature-dependent failure and transformation zones in 2D silica glass through quasistatic Gaussian Phase Packets
New Submission | Disordered Systems and Neural Networks (cond-mat.dis-nn) | 2025-07-21 20:00 EDT
Miguel Spínola, Shashank Saxena, Franz Bamer, Dennis M. Kochmann
The athermal quasistatic (AQS) method is a powerful technique to study the mechanical behavior of disordered systems. However, its applicability is limited to temperatures near zero, where thermal activation is unlikely. In this work, we extend the AQS method to finite temperatures, based on a formulation that describes atoms as temperature-dependent Gaussian packets (GPPs) in phase space under quasistatic conditions, thus equivalent to minimum free energy conditions. This framework is used to study the effect of temperature on the onset of inelasticity and fracture in amorphous two-dimensional silica glass approaching quasistatic conditions under uniaxial tensile loading. An important characteristic of this formulation is the directional dependence of the variance of each Gaussian packet in configuration space, making this formulation an inexpensive and accurate predictor of zones prone to atomic-scale rearrangements, both in the undeformed state and (with increasing accuracy) as the deformation progresses. This method is also shown to accurately capture the thermal expansion of the disordered material. Furthermore, combining the GPP description with Metropolis sampling predicts the effect of temperature on the onset of fracture of the material, which is validated through MD simulations at strain rates as low as $ 10^{4}$ s$ ^{-1}$ . The presented framework therefore provides a valuable technique for studying the nonlinear mechanics of disordered materials at finite temperature and for predicting local rearrangement zones in disordered solids efficiently without the need for expensive MD simulations.
Disordered Systems and Neural Networks (cond-mat.dis-nn), Materials Science (cond-mat.mtrl-sci)
22 pages, 10 figures
Alignment behavior of 2D diopsides (d-silicates) under the influence of an AC electric field
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-07-21 20:00 EDT
Himakshi Mishra, Bruno Ipaves, Raphael Benjamim de Oliveira, Marcelo Lopes Pereira Junior, Raphael Matozo Tromer, e Douglas Soares Galvao, Chandra Shekar Tiwary
Controlling the alignment of two dimensional (2D) materials is crucial for optimizing their electronic and mechanical properties in next generation devices. This study explores how electric fields can manipulate the orientation of 2D diopside (CaMgSi2O6) flakes, a flexible silicate material, through a phenomenon called flexoelectricity, where applied voltage generates mechanical strain. We exfoliated diopside crystals into ultrathin flakes, placed them on microelectrodes, and used AC electric fields to induce alignment via acoustic strain. Raman spectroscopy showed that the flakes reoriented/realigned under the field, with vibrational peaks weakening most at high frequencies (10 MHz). Electrical tests revealed this alignment improves conductivity by 20-30%, as straightened flakes create better pathways for current flow. Fully atomistic molecular dynamics simulations further explained how these flakes naturally align on surfaces within picoseconds, matching our experimental observations. Together, these findings demonstrate a practical way to tune diopside properties using electric fields, opening doors for its use in flexible electronics, sensors, and energy devices.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Materials Science (cond-mat.mtrl-sci)
Excitonic Insulator and the Extended Falicov–Kimball Model Away from Half-Filling
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-07-21 20:00 EDT
D. I. Golosov (Bar-Ilan Univ., Israel)
We consider an extended spinless Falicov–Kimball model at an arbitrary doping level, focusing on the range of parameter values where a uniform excitonic insulator is stabilised at half-filling. We compare the properties of possible uniform phases and construct the Hartree–Fock phase diagrams, which include sizeable phase separation regions. It is seen that the excitonic insulator can appear as a component phase in a mixed-phase state in a broad interval of doping levels. In addition, in a certain range of parameter values the excitonic metal (doped excitonic insulator) is identified as the lowest-energy uniform phase. We suggest that this phase, which is unstable with respect to phase separation, may be stabilised when the phase separation is suppressed by the long-range Coulomb interaction. Overall, we find that excitonic correlations can affect the behaviour of the system relatively far away from half-filling.
Strongly Correlated Electrons (cond-mat.str-el), Materials Science (cond-mat.mtrl-sci)
11 pages LaTeX-Revtex, 7 PostScript figures
Density Matrix Geometry and Sum Rules
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-07-21 20:00 EDT
Guangyue Ji, David E. Palomino, Nathan Goldman, Tomoki Ozawa, Peter Riseborough, Jie Wang, Bruno Mera
Geometry plays a fundamental role in a wide range of physical responses, from anomalous transport coefficients to their related sum rules. Notable examples include the quantization of the Hall conductivity and the Souza-Wilkens-Martin (SWM) sum rule – both valid at zero temperature, independent of interactions and disorder. The finite-temperature generalization of the SWM sum rule has been explored in the literature, revealing deep connections to the geometry of density matrices. Building on recent advances in time-dependent geometric frameworks, we propose a time-dependent quantum geometric tensor for thermal density matrices. This formalism provides a unified interpretation of known sum rules within the framework of the fluctuation-dissipation theorem, further elucidating their fundamental geometric origin. In addition, it provides experimentally accessible methods to probe quantum geometry beyond the zero-temperature regime.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
21 pages
Contact point geometry governs structural build-up at rest in Portland cement-limestone blends
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-07-21 20:00 EDT
Luca Michel, Antoine Sanner, Franco Zunino, Robert J. Flatt, David S. Kammer
The early stiffening of fresh cement paste plays a key role in shaping and stability during casting and 3D printing. In Portland cement systems, this phenomenon arises from the formation of calcium-silicate-hydrate (C-S-H), which stiffens grain-to-grain contacts. However, the role of powder characteristics such as particle size and morphology remains poorly understood. Here, we vary the fineness and grain shape by blending Portland cement with either coarse or fine limestone, leveraging the affinity of C-S-H to nucleate on limestone surfaces. By coupling calorimetry and rheometry, we relate the amount of formed hydration products to the increase in stiffness, and show that the mechanism of contact stiffening through C-S-H formation remains unchanged with limestone addition. Nevertheless, the rate of stiffening varies across blends. We find that these rates correlate with a characteristic length scale that captures particle size and shape. These results demonstrate that early stiffening depends not only on the amount of hydration products formed, but also on the geometry of the contacts where these products form, offering a framework for understanding more complex systems such as limestone-calcined clay cements.
Soft Condensed Matter (cond-mat.soft)
Real time observation of glass-like carbon formation from SU-8 using X-ray and ultraviolet photoelectron spectroscopy
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-21 20:00 EDT
Simon Astley, Jaspa Stritt, Soumen Mandal, Jerome A. Cuenca, D. Andrew Evans, Oliver A. Williams
The structural development and change in elemental composition of SU-8 3005 photoresist into glass-like carbon due to pyrolysis up to 1000$ \degree$ C is investigated utilising \textit{in-situ} x-ray and ultraviolet photoelectron spectroscopy (XPS/UPS) under ultra-high vacuum (UHV). XPS spectra were analysed in order to investigate changes to elemental composition and physical structure. Peak asymmetry in the measured C 1s spectra is found to be a clear indicator of a transition in both physical structure and increased electrical conductivity. The \textit{in-situ} XPS measurement of pyrolysis is effective in isolating changes in oxygen composition solely due to the pyrolysis process. Oxygen concentration, C 1s peak asymmetry and C 1s peak positions are strong indicators of semiconducting SU-8 transitioning to conducting glass-like carbon. For SU-8 pyrolysed above temperatures of 500$ \degree$ C, a clear development is observed in the material structure and composition towards a carbon rich conducting network indicative of glass-like carbon. UPS spectra were analysed to investigate the changes in secondary electron cut-off (SECO) and valence band maximum (VBM) as the SU-8 layer is heated in UHV. The changes in SECO and VBM correlates well with the XPS data and a zero binding energy state is observed at 1000~$ \degree$ C.
Materials Science (cond-mat.mtrl-sci)
Multiscale contact mechanics for elastoplastic contacts
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-07-21 20:00 EDT
Andreas Almqvist, Bo N. J. Persson
Understanding contact between rough surfaces undergoing plastic deformation is crucial in many applications. We test Persson’s multiscale contact mechanics theory for elastoplastic solids, assuming a constant penetration hardness. Using a numerical model based on the boundary element method, we simulate the contact between a rough, rigid surface and an elastic-perfectly plastic half-space with a flat surface. The theory’s predictions for elastic, plastic, and total contact area agree quantitatively with the numerical results. The simulations also support the boundary conditions assumed in the theory, namely that the stress probability vanishes at both zero and yield stress. These findings reinforce the validity of the theory for systems with constant hardness.
Soft Condensed Matter (cond-mat.soft), Materials Science (cond-mat.mtrl-sci)
Predicting interface and spin states in armchair graphene nanoribbon junctions
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-07-21 20:00 EDT
Sofia Sanz, Daniel Sánchez-Portal
We present a theoretical analysis of interface states emerging at junctions between armchair graphene nanoribbons of varying widths. By exploring diverse width combinations and junction geometries, we demonstrate that predicting the precise number of interface states requires considerations beyond the topological classification alone; specifically, the width differences and bonding configuration at the interface play crucial roles. For junctions involving ribbons with small gaps, we further examine how an applied strain affects their topological properties and, consequently, the interface states formed. The spin states at these junctions are investigated using the mean-field Hubbard model, revealing how the magnetic behavior at the interface depends on the number of localized states present. These results are summarized in a series of ``rules of thumb” to predict the number of localized states and the magnetic moment at the junction. Our findings contribute to understanding and engineering localized states in graphene-based devices, providing guidelines for manipulating electronic and magnetic properties through structural design.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Emergent topology by Landau level mixing in quantum Hall-superconductor nanostructures
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-07-21 20:00 EDT
Yuriko Baba, Alfredo Levy Yeyati, Pablo Burset
We demonstrate the emergence of novel topological phases in quantum Hall-superconductor hybrid systems driven by Landau level mixing and spin-orbit interactions. Focusing on a narrow superconducting stripe atop a two-dimensional electron gas, we identify regimes where the hybridization of the chiral Andreev states at each side of the stripe leads to different phases beyond the long sought $ p$ -wave superconducting one. These topological phases exhibit distinctive transport signatures, including quantized nonlocal conductance arising from electron cotunneling at filling factor $ \nu=1$ , which can coexist with quantized crossed Andreev reflection at $ \nu=2$ . A combination of numerical simulations and effective modelling reveals the role of spin-orbit coupling and stripe geometry in controlling these transitions. Our findings suggest new strategies for realizing and detecting topology in proximized quantum Hall devices.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Superconductivity (cond-mat.supr-con)
13 pages; 11 figures
Strongly correlated altermagnet CaCrO$_3$
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-07-21 20:00 EDT
Zhenfeng Ouyang, Peng-Jie Guo, Rong-Qiang He, Zhong-Yi Lu
Altermagnetism, a newly discovered magnetic phase, has spurred growing research activity. Studies from a perspective of dynamical electronic correlation still remain scarce. Employing density functional theory plus dynamical mean-field theory (DFT+DMFT) that incorporates dynamical electronic correlation, we demonstrate that CaCrO$ _3$ is a strongly correlated altermagnet. Our DFT+DMFT calculations successfully reproduce the correlated metallic behavior of CaCrO$ _3$ and quantitatively capture the incoherence state observed experimentally. We also identify that the altermagnetic CaCrO$ _3$ is a Hund’s metal with a non-Fermi liquid behavior. Moreover, we find that altermagnetism can induce flat bands, and these incipient flat bands are further promoted by the strong renormalization from Hundness, which drives a heavy-fermion behavior. Hence, we propose that Hund’s metals provide an ideal platform for hosting novel strongly correlated altermagnetism. Our work will promote the study of strongly correlated altermagnetism physics.
Strongly Correlated Electrons (cond-mat.str-el), Materials Science (cond-mat.mtrl-sci)
6 pages, 4 figures, 1 table
Ex Situ Fabrication of Superconducting Nanostructures for Low-Temperature STM
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-21 20:00 EDT
Adrian Greichgauer, Roozbeh Yazdanpanah, Alexey Taskin, Oliver Breunig, Yoichi Ando, Jens Brede
Nanofabrication enables flexible experimental design but is often incompatible with scanning tunneling microscopy and spectroscopy (STM/STS) due to the latter’s stringent surface quality requirements. Here, we present a fabrication strategy that combines ex situ nanolithography with in situ ultrahigh-vacuum (UHV) cleaving to produce atomically clean, nanopatterned superconductor/topological insulator (TI) heterostructures suitable for high-resolution STM/STS. In our initial Design I, nanoribbons were defined by etching trenches into a TI film, followed by niobium capping and sample flipping before cleaving. This enabled STM/STS to be applied in large areas, although edge quality was limited by etch debris. To overcome this, we developed Design II, which avoids etching through the film by locally thinning it, leaving nanoscale ribbons raised above a continuous TI layer, followed again by Nb capping and sample flipping before cleaving. This method yields clean, reproducible nanostructures with well-defined superconducting gaps, demonstrating a reliable fabrication pathway for high-resolution STM/STS studies of nanoscale topological devices.
Materials Science (cond-mat.mtrl-sci), Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Superconductivity (cond-mat.supr-con)
29 pages, with 13 figures. Manuscript and Supporting Information
Global $q$-dependent inverse transforms of intensity autocorrelation data
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-07-21 20:00 EDT
Tobias Eklund, Christina M. Tonauer, Felix Lehmkühler, Katrin Amann-Winkel
We present a new analysis approach for intensity autocorrelation data, as measured with dynamic light scattering and X-ray photon correlation spectroscopy. Our analysis generalizes the established CONTIN and MULTIQ methods by direct nonlinear modeling of the $ g_2$ function, enabling decomposition of complex dynamics without a priori knowledge of experimental scaling factors. We describe the mathematical formulation, implementation details, and strategies for solution, as well as demonstrate decompositions of soft matter dynamics data into distributions of diffusion rates/velocities. The open-source MATLAB implementation, including example data, is publicly available for adoption and further development.
Soft Condensed Matter (cond-mat.soft), Data Analysis, Statistics and Probability (physics.data-an)
Fast charge noise sensing using a spectator valley state in a singlet-triplet qubit
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-07-21 20:00 EDT
David W. Kanaar, Yasuo Oda, Mark F. Gyure, J. P. Kestner
Semiconductor spin qubits are a promising platform for quantum computing but remain vulnerable to charge noise. Accurate, in situ measurement of charge noise could enable closed-loop control and improve qubit performance. Here, we propose a method for real-time detection of charge noise using a silicon singlet-triplet qubit with one electron initialized in an excited valley state. This valley excitation acts as a spectator degree of freedom, coupled to a high-quality resonator via the exchange interaction, which is sensitive to charge-noise-induced voltage fluctuations. Dispersive readout of the resonator enables a continuous, classical measurement of exchange fluctuations during qubit operation. Signal-to-noise analysis shows that, under realistic device parameters, sub-microsecond measurement times are possible using a quantum-limited amplifier. Even without such an amplifier, sub-millisecond performance is achievable with appropriately engineered resonator parameters. This approach allows the probe to monitor slow drift in exchange in real time, opening the door to feedback and feedforward strategies for maintaining high-fidelity quantum operations. Importantly, the protocol preserves spin coherence and can be run concurrently with qubit logic gates.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Quantum Physics (quant-ph)
11 pages, 3 figures
Spatiotemporal Order and Parametric Instabilities from First-Principles
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-07-21 20:00 EDT
Daniel Kaplan, Pavel A. Volkov, Jennifer Coulter, Shiwei Zhang, Premala Chandra
Shaping crystal structure with light is an enduring goal of physics and materials engineering. Here we present calculations in candidate materials selected by symmetry that allow light-induced spatiotemporal parametric instabilities. We demonstrate a theoretical framework that includes a complete symmetry analysis of phonon modes that contribute to parametric instabilities across all non-centrosymmetric point groups, a detailed survey of the materials landscape and finally the computation of nonlinear couplings from first principles. We then showcase detailed results for chiral crystals, ferroelectrics, and layered van der Waals materials. Our results pave the way towards realizing designer time-crystalline order in quantum materials, detectable with time-resolved diffractive probes.
Materials Science (cond-mat.mtrl-sci), Disordered Systems and Neural Networks (cond-mat.dis-nn), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
9 page + 2 appendices. 8 Figures. Comments welcome
Anyonic analogue of optical Mach-Zehnder interferometer
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-07-21 20:00 EDT
Navketan Batra, Zezhu Wei, Smitha Vishweshwara, D. E. Feldman
Anyonic interferometry is a direct probe of fractional statistics. We propose an interferometry geometry that parallels an optical Mach-Zehnder interferometer and offers several advantages over existing interferometry schemes. In contrast to the currently studied electronic Mach-Zehnder interferometer, our setup has no drain inside the device so that the trapped topological charge is time-independent. In contrast to electronic Fabry-Pérot interferometry, anyons cannot go around the device more than once. Thus, the interference signal has a straightforward interpretation in terms of anyonic statistical phases. The proposed geometry suppresses the undesirable effects of bulk-edge coupling. Moreover, the setup allows for simple exact solutions for the electric current and noise for an arbitrary quasiparticle tunneling strength in a broad range of conditions. The structure of the solutions is similar to that for non-interacting electrons but reflects fractional charge and statistics. We present results for electric current and noise in Jain states and address thermal interferometry at zero voltage bias.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Strongly Correlated Electrons (cond-mat.str-el)
25 pages, 8 figures
Design framework for programmable three-dimensional woven metamaterials
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-07-21 20:00 EDT
Molly Carton, James Utama Surjadi, Bastien F.G. Aymon, Carlos M. Portela
Mechanical metamaterials have continued to offer unprecedented tunability in mechanical properties, but most designs to date have prioritized attaining high stiffness and strength while sacrificing deformability. The emergence of woven lattices-three-dimensional networks of entangled fibers-has introduced a pathway to the largely overlooked compliant and stretchable regime of metamaterials. However, the design and implementation of these complex architectures has remained a primarily manual process, restricting identification and validation of their full achievable design and property space. Here, we present a geometric design framework that encodes woven topology using a graph structure, enabling the creation of woven lattices with tunable architectures, functional gradients, and arbitrary heterogeneity. Through use of microscale in situ tension experiments and computational mechanics models, we reveal highly tunable anisotropic stiffness (varying by over an order of magnitude) and extreme stretchability (up to a stretch of four) within the design space produced by the framework. Moreover, we demonstrate the ability of woven metamaterials to exhibit programmable failure patterns by leveraging tunability in the design process. This framework provides a design and modeling toolbox to access this previously unattainable high-compliance regime of mechanical metamaterials, enabling programmable large-deformation, nonlinear responses.
Soft Condensed Matter (cond-mat.soft)
35 pages, 5 main text Figures, 11 Supplementary Figures
Learning the non-Markovian features of subsystem dynamics
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-07-21 20:00 EDT
Michele Coppola, Mari Carmen Bañuls, Zala Lenarčič
The dynamics of local observables in a quantum many-body system can be formally described in the language of open systems. The problem is that the bath representing the complement of the local subsystem generally does not allow the common simplifications often crucial for such a framework. Leveraging tensor network calculations and optimization tools from machine learning, we extract and characterize the dynamical maps for single- and two-site subsystems embedded in an infinite quantum Ising chain after a global quench. We consider three paradigmatic regimes: integrable critical, integrable non-critical, and chaotic. For each we find the optimal time-local representation of the subsystem dynamics at different times. We explore the properties of the learned time-dependent Liouvillians and whether they can be used to forecast the long-time dynamics of local observables beyond the times accessible through direct quantum many-body numerical simulation. Our procedure naturally suggests a novel measure of non-Markovianity based on the distance between the quasi-exact dynamical map and the closest CP-divisible form and reveals that criticality leads to the closest Markovian representation at large times.
Statistical Mechanics (cond-mat.stat-mech), Quantum Physics (quant-ph)
24 pages, 11 figures