Soft Condensed Matter
Anomalously Large Screening Lengths in Highly Concentrated Electrolytes: A Matter of Experimental Conditions
Thomas Tilger, Esther Ohnesorge, Michalis Tsintsaris et al. (+4 more)
Considerable debate exists about anomalous underscreening. Whilst surface force apparatus (SFA) measurements have confirmed anomalously large screening lengths ($\lambda$) in concentrated aqueous electrolytes, colloidal probe atomic force microscopy (CP-AFM) measurements have not. We demonstrate that by tuning experimental conditions, similarly large $\lambda$ can be achieved in concentrated aqueous LaCl$_3$ electrolytes with CP-AFM. Structural forces were also observed at high LaCl$_3$ concentrations, which we suggest stem from the formation of diffuse ion clusters, and that the remaining counter-ions yield the large deduced $\lambda$.
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All authors Thomas Tilger, Esther Ohnesorge, Michalis Tsintsaris, Nithya Hellar, Kazue Kurihara, Hayden Robertson, Regine von Klitzing
Materials Science
Structural phase transitions in double perovskite crystals studied by Brillouin light scattering
D. O. Horiachyi, M. O. Nestoklon, I. A. Akimov et al. (+5 more)
Inorganic lead-free double perovskites represent particular interest as non-toxic and stable material platform for optoelectronic applications. Here, we employ Brillouin light scattering spectroscopy to investigate the elastic properties and structural phase transitions in single
crystals of Cs2AgBiBr6 and Cs2AgBiCl6. A complete set of elastic constants is determined from the Brillouin scattering measurements performed along three different crystallographic directions. Both materials exhibit similar elastic constants and weak elastic anisotropy in the cubic phase. At low temperatures, the lifting of degeneracy of transverse acoustic
phonon modes is attributed to a lowering of
crystal symmetry. From the temperature dependence of the acoustic
phonon frequencies, we determine the structural phase transition temperature of about 43 K for Cs2AgBiCl6, compared to 122 K for the cubic-to-tetragonal phase transition in Cs2AgBiBr6.
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All authors D. O. Horiachyi, M. O. Nestoklon, I. A. Akimov, D. R. Yakovlev, V. Vasylkovskyi, O. Trukhina, V. Dyakonov, M. Bayer
Superconductivity
On the estimating the superconducting volume fraction from the internal magnetic susceptibility
Aleksandr V. Korolev and Evgeny F. Talantsev
Zhang et al.$^1$ reported zero-field cooled (ZFC) and field cooled (FC) data measured in a highly compressed $Pr_4Ni_3O_{10}$ single
crystal. These measurements provide unambiguous confirmation of bulk superconductivity in pressurized Ruddlesden-Popper nickelates. Zhang et al.$^1$ applied an equation (described in Refs.$^{2,3}$) to recalculate ZFC data measured in a $Pr_4Ni_3O_{10}$ (sample S3) in volume fraction $f$ of the superconducting phase in the sample. In result$^1$, $f = 0.85$ was reported for sample S3 at pressure P = 40.2 GPa. The key postulate of the methodology for the calculation of $f$ (see also works$^{4-6}$) is that $f$ is equal to the amplitude of the internal
magnetic susceptibility $\vert \chi_{internal} \vert $, or $ f = \vert \chi_{internal} \vert $. Here we argue that this postulate is incorrect and present counterexample where the $Pr_4Ni_3O_{10}$ sample S3 can exhibit $f < 0.10$ and $\vert \chi_{internal} \vert = 0.82 $. In the result, we addressed recent Replies$^{2,3}$ on our Comments$^{7,8}$. Considering that the postulate $ f = \vert \chi_{internal} \vert $ is widely used in superconductivity, we extend our request to reconsider the validity of this postulate in the entire field of superconductivity.
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Soft Condensed Matter
A thermodynamic metric quantitatively predicts disordered protein partitioning and multicomponent phase behavior
Zhuang Liu, Beijia Yuan, Mihir Rao et al. (+2 more)
Intrinsically disordered regions (IDRs) of
proteins mediate sequence-specific interactions underlying diverse cellular processes, including the formation of biomolecular condensates. Although IDRs strongly influence condensate compositions, quantitative frameworks that predict and explain their phase behavior in complex mixtures remain lacking. Here we introduce a thermodynamic model that quantitatively predicts the behavior of arbitrary combinations of IDRs across a wide range of concentrations, with accuracy comparable to state-of-the-art simulations. The model learns low-dimensional, context-independent representations of IDR sequences that combine to form mixture representations, producing context-dependent interactions. These representations define a thermodynamic metric space in which distances between IDRs correspond directly to differences in their thermodynamic properties. We show that the model predicts multicomponent phase diagrams in quantitative agreement with molecular simulations without being trained on free-energy or phase-coexistence data. The metric space provides geometrically intuitive predictions of IDR partitioning, multicomponent condensation, and context-dependent mutational effects, addressing several central problems in IDR biophysics within a single model. Systematic interrogation of the learned representations reveals how amino-acid composition and sequence patterning jointly determine mixture thermodynamics. Together, our results establish a unified and interpretable framework for predicting and understanding the behavior of complex mixtures of IDRs and other sequence-dependent biomolecules.
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All authors Zhuang Liu, Beijia Yuan, Mihir Rao, Gautam Reddy, William M. Jacobs
Materials Science
Atomic-resolution imaging of gold species at organic liquid-solid interfaces
Sam Sullivan-Allsop, Nick Clark, Wendong Wang et al. (+26 more)
Understanding solid-
liquid interfaces at the atomic-scale is key to improved performance of heterogeneous catalysts, electrodes and membranes. Here we combine unique specimen design, record atomic resolution in situ electron microscopy, and artificial intelligence-enabled analysis to achieve a step change in quantitative understanding of interfacial atomic behaviour. We create the first
graphene liquid cells with organic solvents and employ them to track over 106 gold adatoms and clusters at a
graphene surface immersed in acetone and cyclohexanone. We reveal dynamic correlated behaviour of gold adatom monomers, dimers, trimers and clusters, strongly influenced by each other, the solvent properties, and the atomic
lattice of the substrate, in good agreement with theoretical calculations. We use the results to interpret differences in catalytic activity towards the industrially important acetylene hydrochlorination reaction. This new capability for exploration of atomic scale chemistry could enable rational design of future catalysts, membranes and electrodes with improved functionality.
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All authors Sam Sullivan-Allsop, Nick Clark, Wendong Wang, Rongsheng Cai, William Thornley, David G. Hopkinson, James G. McHugh, Ben Davies, Samuel Pattisson, Nicholas F. Dummer, Rui Zhang, Matthew Lindley, Gareth Tainton, Jack Harrison, Hugo De Latour, Joseph Parker, Joshua Swindell, Eli G. Castanon, Amy Carl, David J. Lewis, Natalia Martsinovich, Christopher S. Allen, Mohsen Danaie, Andrew J. Logsdail, Vladimir Falko, Graham J. Hutchings, Alex Summerfield, Roman Gorbachev, Sarah J. Haigh
Strongly Correlated Electrons
Magnetic phase diagram and spin Hamiltonian of antiferromagnet Cs$_2$CoI$_4$
S.D. Nabi, L. Facheris, V. Romerio et al. (+12 more)
We report comprehensive thermodynamic and
neutron scattering measurements on the $S$ = 3/2 antiferromagnet Cs$_2$CoI$_4$, a member of the thoroughly studied family of frustrated magnets Cs$_2MX_4$ ($M$ = Cu, Co, Ru, $X$ = Br, Cl, I, O). Unlike previously studied members, Cs$_2$CoI$_4$ undergoes a structural phase transition, for which we determine the low-temperature crystallographic structure. The resulting
symmetry reduction strongly affects both the
magnetic exchange interactions and single-ion anisotropy. Despite the large parameter space, we propose a minimal
magnetic Hamiltonian that reasonably captures the observed excitation spectrum, analyzed using extended SU(4) linear
spin-wave theory.
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All authors S.D. Nabi, L. Facheris, V. Romerio, V. Kocsis, K. Yu. Povarov, D. Sheptyakov, J. Lass, D.G. Mazzone, H. Kikuchi, T. Masuda, S.A. Barnett, D.R. Allan, Z. Yan, S. Gvasaliya, A. Zheludev
Materials Science · Cross-listed from physics.optics
Large differential attosecond delays in solid state photoemission
Andreas Gebauer, Walter Enns, Sergej Neb et al. (+11 more)
Time-resolved photoelectron spectroscopy provides access to the electronic structure and non-
equilibrium electron dynamics in matter. At solid surfaces photoemission dynamics can be investigated on its natural time scale by measuring attosecond time delays of emitted electrons. Photoelectrons with final state energies of several tens of eV need tens to hundreds of attoseconds to be released into the
vacuum. Competing effects determine the emission dynamics and, hence, the full picture of the process is still under debate. The rather large energy differences between the final states probed in commonly reported relative photoemission delays obscure their complex fine structure and hinders the interpretation of the measurements. Here we report differential attosecond delays $\tau_{\mathrm{DAD}}$, i.e., relative photoemission delays for energetically close-lying
spin-orbit split states. Differential attosecond delays on the order of 30 to 100 as for Bi 5d, Te 4d, and Se 3d core level photoemission from Bi$_2$Te$_3$ and Bi$_2$Se$_3$ can neither be attributed to intra-atomic delays, nor to ballistic transport and subsequent emission. Instead, calculations based on the one-step photoemission theory reveal that photoemission delays vary strongly on the energy scale of the
spin-orbit splitting and quantitatively match experimental observations. This strong variation arises from multiple scattering at the surface leading to final states that involve both evanescent and propagating Bloch waves. Their relative amplitudes vary strongly affecting thereby the timing of the photoemission event since evanescent and propagating components exhibit inherently different dynamics.
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All authors Andreas Gebauer, Walter Enns, Sergej Neb, Tillmann Schabbehard, Luis Maschmann, Stefan Muff, J. Hugo Dil, Ulrich Heinzmann, Stephan Fritzsche, Ricardo Diez Muiño, Pedro M. Echenique, Nikolay M. Kabachnik, Eugene E. Krasovskii, Walter Pfeiffer
Soft Condensed Matter · Cross-listed from physics.flu-dyn
Adaptive shape control for microswimmer navigation in turbulence
Jingran Qiu, Lorenzo Piro, Luca Biferale et al. (+3 more)
Navigation in turbulent environments is a fundamental challenge for biological and artificial microswimmers. While most existing studies focus on adapting motility or steering, the role of active morphological changes in
navigation remains poorly explored. Here, we investigate a shape-changing spheroidal microswimmer tasked with maximising its displacement from an initial position in two-dimensional
stochastic and turbulent flows. Using reinforcement learning (RL), the microswimmer learns to adapt its aspect ratio based on its orientation and local velocity-gradient signals. The learned strategies outperform fixed-shape and short-time-optimal baselines across different flow regimes and remain effective when transferred from
stochastic flows to fully resolved
turbulence. Guided by the learned policies, we propose a minimal analytical model that captures the essential
navigation mechanisms and reproduces the performance across flow regimes. These results show that adaptive morphology provides a robust and physically interpretable control paradigm for microswimmer
navigation in complex flows.
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All authors Jingran Qiu, Lorenzo Piro, Luca Biferale, Massimo Cencini, Bernhard Mehlig, Kristian Gustavsson
Materials Science
Strain-driven magnetic anisotropy and spin reorientation in epitaxial Co V 2 O 4 spinel oxide thin films
Lamiae El Khabchi, Laurent Schlur, Jérôme Robert et al. (+9 more)
CoV___O___ (CVO) stands out among spinel vanadates for its ultra-short V-V distances, placing it at the brink of itinerant electron behaviour-an ideal playground for strain engineering. In this work, we exploit this sensitivity by growing high-quality epitaxial CVO thin films on SrTiO___ (001) and MgO (001), inducing compressive and tensile strain, respectively. Using pulsed
laser deposition under ultra-low oxygen pressure, we achieve high crystalline quality and straincontrolled tetragonal distortions: c > a under compression (STO) and c < a under tension (MgO). Resonant elastic X-ray scattering confirms a normal spinel structure, with cobalt occupying tetrahedral sites and vanadium octahedral ones. Both strain types reduce charge transport, driving the system into a highly resistive state.
Magnetic measurements reveal strain-driven anisotropy switching: STO films transition from out-of-plane to in-plane easy axis below 90 K, while MgO films flip from in-plane to out-of-plane below 45 K. These results highlight CVO's exceptional responsiveness to
lattice strain, unlocking a path to finely tunable electronic and
magnetic properties. With its strong
spin-
lattice coupling and potential in
spin Hall magnetoresistance, strained CVO emerges as a compelling platform for next-generation lowpower spintronic devices.
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All authors Lamiae El Khabchi, Laurent Schlur, Jérôme Robert, Marc Lenertz, Cédric Leuvrey, Gilles Versini, François Roulland, Gilbert Chahine, Nils Blanc, Daniele Preziosi, Christophe Lefèvre, Nathalie Viart
Mesoscale and Nanoscale Physics
All-in-plane image sensors free from readout integrated circuits
Kirill Kapralov, Ilya Mazurenko, Elizaveta Tarkaeva et al. (+12 more)
High resolution image sensors require electrical access to each individual pixel for signal readout. Such access is especially challenging for ultra-miniaturized pixels, for heterogeneously integrated sensing and readout layers in long-wavelength detectors, and for novel light-sensing materials with unestablished integration to silicon chips. Here, we introduce and experimentally validate a novel imaging approach that does not require electrical connections to individual pixels. The sensor
matrix involves photoresistive pixels connected neighbor-to-neighbor and packed into a rectangular
lattice. The signal readout is based on electrical impedance
tomography applied to the photoresistance: the photovoltage is measured at the
matrix boundary at various positions of injected bias current, and the image is reconstructed algorithmically. We present experimental validations for moderate-size infrared imagers based on multilayer
graphene (24 pixels) and amorphous vanadium
oxide (264 pixels). The reconstruction procedure is mathematically stable, sustainable to variations of pixel resistivity and photosensitivity, and its complexity is that of linear system solution. The proposed method enables unprecedented architecture simplification of imaging devices.
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All authors Kirill Kapralov, Ilya Mazurenko, Elizaveta Tarkaeva, Valentin Semkin, Oleg Kononenko, Maxim Knyazev, Viktor Matveev, Mikhail Kashchenko, Alexander Morozov, Ivan Domaratsky, Vladimir Kaydashev, Yana Litun, Aleksandr Kuntsevich, Alexey Bocharov, Dmitry Svintsov
Mesoscale and Nanoscale Physics
Layer-Dependent Orbital Magnetization in Graphene-Haldane Heterostructures
Sovan Ghosh and Bheema Lingam Chittari
Rhombohedral multilayer
graphene (RMG) proximity-coupled to a Haldane substrate provides a platform to investigate the interplay between band
topology, layer number, and electric-field control of orbital magnetism. Using a tight-binding model and the modern theory of orbital magnetization, we study the layer-dependent
magnetic response in
bilayer, trilayer, tetralayer and pentalayer
graphene under Haldane proximity. While monolayer
graphene develops a global topological gap with quantized magnetization slope, multilayer systems remain metallic due to protected low-energy bands associated with unperturbed sublattices. Despite the absence of a global gap, finite valley-contrasting Berry
curvature produces non-trivial layer-dependent Chern numbers. We decompose the total orbital magnetization into self-rotation ($M_{\mathrm{SR}}$) and center-of-mass ($M_C$) contributions, revealing their distinct behaviors across doping and applied interlayer bias. In
bilayer graphene, magnetization remains negative and monotonic. Remarkably, trilayer and tetralayer
graphene display a bias-induced sign reversal of orbital magnetization beyond critical thresholds ($\Delta \simeq -55$ meV for 3LG, $-50$ meV for 4LG) in the hole-doped regime, a feature completely absent in the
bilayer. It is further established in the case of 5LG, that the magnetization reversal is independent of the topological transition, and depends on the direction of bias and hole doping. The effect persists across both hole and electron doping, demonstrating that layer count serves as a key tuning parameter for orbital magnetism. Our findings establish topologically proximitized multilayer
graphene as a versatile platform for electric-field-manipulable orbitronic and valleytronic devices.
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Superconductivity
Enhancement of metallicity by Na doping in La$_3$Ni$_2$O$_{7+{\delta}}$
Yingying Gao, Wei Zhou, W. H. Guo et al. (+6 more)
The observation of high-$T_c$ superconductivity in
bilayer nickelate La$_3$Ni$_2$O$_7$ under high pressure provides a new venue for exploring novel unconventional
superconductors and elucidating the mechanism of high-$T_c$ superconductivity. Subsequently, numerous chemical substitution studies have been reported, aiming to stabilize superconductivity at ambient pressure, or significantly reduce the pressure threshold required for its occurrence. Here, we report the comprehensive study on sodium (Na) doping in the Ruddlesden-Popper nickelate La$_3$Ni$_2$O$_{7+{\delta}}$, where Na$^+$ substitutes for La$^{3+}$ at the A-site with varying doping concentrations. The structural, thermal,
magnetic, and electronic transport properties of as-synthesized polycrystalline samples were systematically investigated. X-ray diffraction (XRD) analysis reveals that Na doping induces a structural transition from the '327' Amam phase to the '4310' Bmab phase when $x\geq0.075$, which is further corroborated by thermogravimetric analysis (TGA) measurements. Substitution of La$^{3+}$ with Na$^+$ gives rise to a gradual expansion of the '327' phase
lattice. Meanwhile, resistivity measurements indicate that the density wave (DW) transition is marginally suppressed and
metallicity is significantly enhanced. Upon the application of pressure, DW transition can be further suppressed, whereas the low-$T$ insulating behaviors remain insensitive to pressure. These results offer critical insights into the roles of elemental substitution and charge carrier doping in steering the competing electronic phases in layered nickelates.
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All authors Yingying Gao, Wei Zhou, W. H. Guo, Chunqiang Xu, H. F. Chen, Z. D. Han, Xiaofeng Xu, Yinzhong Wu, Bin Qian
Materials Science · Cross-listed from physics.class-ph
Unimode material based low-frequency underwater acoustic isolation
Yu Wei, Binghao Zhao, Fen Du et al. (+2 more)
Extremal materials are a specific class of Cauchy materials whose elasticity tensor has one or more zero
eigenvalues. Each zero
eigenvalue corresponds to a soft mode requiring zero strain energy, while non-zero
eigenvalues correspond to hard modes that cost energy. According to the number, N, of zero
eigenvalues, these materials can be referred to as unimode (N=1), bimode (N=2), etc. Extremal materials have enabled novel functions beyond conventional Cauchy media, e.g.,
phonon polarizers, Rayleigh wave isolators and
underwater acoustic cloaks. These functions typically require a single extremal material. Interfaces between two extremal materials exhibit rich wave behaviors, yet have been seldom explored. Here, we proposed the concept of complementary extremal materials, i.e., the soft mode of one extremal material is a hard mode of the other. As one example, we study the interface between an isotropic unimode material and an isotropic bimode material. We show that the interface allows perfect mode conversion from longitudinal waves to transverse waves. A low-frequency
underwater acoustic
insulator based on complementary extremal materials is proposed. Our finding has been verified with designed metamaterials and using effective-medium modeling. This work demonstrates the potential of complementary extremal materials in controlling elastic wave polarization and waterborne sound.
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All authors Yu Wei, Binghao Zhao, Fen Du, Yi Chen, Gengkai Hu
Materials Science
Unexpected Planar Dislocation Boundary Formation in FCC Metals Captured by Dark-Field X-ray Microscopy and Continuum Dislocation Dynamics
Adam André William Cretton, Khaled SharafEldin, Axel Henningsson et al. (+8 more)
Validating dislocation patterning models against in situ imaging experiments is a longstanding goal in materials physics. Here, we provide the first direct morphological comparison of such models. Using in situ Dark-Field X-ray Microscopy (DFXM), we map the local orientations in high-purity aluminium deformed along [100] and find unexpected planar dislocation boundaries aligned with {111} slip planes that form prior to the development of a conventional dislocation
cell structure. To explain this behaviour, we generate synthetic DFXM contrast images from a continuum dislocation dynamics (CDD) simulation. This mesoscale model, using nickel as a high stacking fault energy (SFE) FCC analogue, independently predicts the formation of the same {111} planar boundary types. This correspondence demonstrates that state-of-the-art CDD and DFXM experimental data can be used synergistically - despite differences in strain rates and length scales - as a practical route for refining continuum theories of plasticity.
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All authors Adam André William Cretton, Khaled SharafEldin, Axel Henningsson, Felix Frankus, Can Y{\i}ld{\i}r{\i}m, Carsten Detlefs, Flemming Bjerg Grumsen, Albert Zelenika, Anter El-Azab, Grethe Winther, Henning Friis Poulsen
Materials Science
Role of photonic interference in exciton-mediated magneto-optic responses
Güven Budak, Christian Riedel, Akashdeep Kamra et al. (+4 more)
Coupled optical and
magnetic excitations can give rise to remarkably strong magneto-optic responses. This is particularly evident in van der Waals magnets, such as the antiferromagnet CrSBr, where
excitons and
magnons emerge from the same electronic orbitals. While previous work has primarily focused on uncovering the magneto-electric origin of the resulting
exciton-
magnon interactions, the influence of photonic effects has received comparatively little
attention. Here, we use numerical simulations to disentangle
exciton-
magnon coupling from the
exciton-mediated
magnon-
photon interactions observed in optical experiments. Our simulations show the strong dependence of these interactions on photonic interference and dispersion effects near excitonic resonances. Such effects shape the optical response to coherent
magnons and make it intrinsically non-linear in the
magnon-induced
exciton energy shift. Thermal
magnons, which have a particularly pronounced impact on
excitons, are found to even produce qualitatively different trends in optical signatures. Depending on weak or strong coupling of
excitons and
photons, the same
exciton-
magnon interaction can lead to a red-shift of optical modes, a nearly vanishing response, or their blue-shift. Finally, we demonstrate first steps towards optimizing the multi-parameter problem of efficient
magnon-
photon transduction using a machine-learning approach.
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All authors Güven Budak, Christian Riedel, Akashdeep Kamra, Patrick Rinke, Christian Back, Matthias Stosiek, Florian Dirnberger
Soft Condensed Matter
Probing scale-dependent liveliness with nonequilibrium thermospectroscopy
Joscha Mecke and Klaus Kroy
Probing the spatially heterogeneous activity across scales is a major challenge in living matter. Energy injection at diverse length scales leads to mode coupling, inter-modal energy transfer, and
entropy production. We demonstrate the emergence of multiple effective (“active”) temperatures in nonequilibrium molecular- and Brownian-dynamics simulations of an active
polymer. Via a generalised Langevin equation for a labelled monomer we identify spectral noise temperatures and their relation to the underlying activity landscape. A harmonic trap of variable stiffness can serve as a minimally invasive prototypical spectroscopic device to selectively scan through the emergent effective temperatures and thereby resolve the scale-dependent activity.
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Materials Science
Shape Selection in Nanopillar Formation
Marta A. Chabowska and Magdalena A. Załuska-Kotur
Crystal growth processes produce a diverse array of surface formations, primarily distinguished by their
geometric shapes. While some structures strictly adhere to the underlying
crystal symmetry, others exhibit universal circular or oval geometries. Utilizing Vicinal Cellular Automata (VicCA) modeling, we demonstrate that these morphological differences depend on the spatial distribution of the growth potential. Specifically, local potential variations concentrated around surface steps drive the formation of the
lattice symmetry - following structures, whereas global potentials - often originating from defects-generate universal spherical or oval shapes. Furthermore, we illustrate how these morphologies are influenced by the growth parameters such as sticking coefficient or
diffusion coefficient. Although the positioning of surface defects is difficult to control, we show that temperature and external particle flux can be effectively used to steer and manipulate surface pattern formation.
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Materials Science
Rethinking Charge Transport and Recombination in Donor-diluted Organic Solar Cells
Chen Wang, Christopher Wöpke, Toni Seiler et al. (+12 more)
We systematically investigate PM6:Y12 bulk-heterojunction
solar cells with donor fractions ranging from 1% to 45%, linking morphology, charge transport, and recombination to device performance. Complementary structural and spectroscopic methods reveal that a percolating PM6 network forms even at below 5% donor content, with lamellar stacking and vertical composition gradients that do not hinder the charge extraction. The reduction of the effective active layer conductivity towards low donor fractions obeys a three-dimensional percolation model, indicating that charge transport is governed by network
topology rather without a pronounced percolation threshold. A transition from nongeminate Langevin recombination to a dispersive Smoluchowski-type loss occurs below 5% donor fraction. The latter regime is also nongeminate, i.e., pertains to recombination of the total charge carrier density. Correspondingly, we observe that the Langevin reduction in the higher donor fractions - mostly dominated by redissociation of electron-hole pairs after encounter - changes towards low donor fractions: in these cases, the nongeminate loss rate exceeds the prediction of the Langevin model. This regime coincides with increasing transport resistance due to
topology-limited hole conduction, leading to reduced fill factors despite a high retained charge-generation efficiency. Our results demonstrate that strong donor dilution preserves photogeneration if a continuous donor network is maintained, and unveil how
topology-controlled transport and non-Langevin recombination jointly define the performance limits of donor-diluted organic
solar blends.
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All authors Chen Wang, Christopher Wöpke, Toni Seiler, Jared Faisst, Mathias List, Meike Kuhn, Bekcy Joseph, Alexander Ehm, Dietrich R. T. Zahn, Yana Vaynzof, Eva M. Herzig, Roderick C. I. Mackenzie, Uli Würfel, Maria Saladina, Carsten Deibel
Materials Science
The giant anomalous Hall and Nernst effects in Kagome permanent magnets RCo5
Weian Guo, Pengyu Zheng, Rui Liu et al. (+3 more)
Kagome
lattice materials have attracted considerable
attention due to their intriguing topological properties and potential applications in next-generation
quantum and spintronic technologies. In particular, rare-earth permanent magnets with Kagome structure provide an ideal platform that combines robust magnetism with nontrivial
quantum phenomena. However, their anomalous transport properties, particularly thermoelectric responses, remain insufficiently explored. In this work, we perform systematic first-principles calculations on the anomalous
Hall and anomalous Nernst effects in Kagome permanent magnets RCo5 (R = Ce, La, Sm, Gd). We find that CeCo5 exhibits a pronounced anomalous
Hall conductivity of about 1500 Omega^-1 cm^-1 while GdCo5 displays a substantial anomalous Nernst conductivity of 11 A m^-1 K^-1 within +/- 0.1 eV of the
Fermi energy, both comparable to or surpassing the measured intrinsic values reported in many typical Weyl and Heusler magnets. These exceptional anomalous transport properties originate from Berry
curvature hotspots near
spin-orbit coupling induced band gaps. If validated, these theoretical predictions would be important for Berry-
curvature-driven transport in
magnetic intermetallics. Our results establish RCo5 compounds as versatile platforms for exploring Berry
curvature-driven transport in tunable
magnetic topological materials.
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All authors Weian Guo, Pengyu Zheng, Rui Liu, Yiran Peng, Ying Yang, Zhiping Yin
Statistical Mechanics
Percolation on multifractal, scale-free weighted planar stochastic porous lattice
Proshanto Kumar and Md. Kamrul Hassan
We introduce the Weighted Planar
Stochastic Porous
Lattice (WPSPL), a geometrically disordered substrate generated by iteratively subdividing a unit square. At each step a block is selected with probability proportional to its area, divided into four parts, and one sub-block is retained (removed) with probability $q$ ($1-q$). We show analytically that the WPSPL exhibits multifractality for each of its infinitely many nontrivial conserved quantities and demonstrate numerically that its snapshots at different times are statistically self-similar. The dual of the
lattice forms a complex network with a power-law degree distribution. Motivated by these properties of this porous
lattice, we study bond percolation on the WPSPL, determine the percolation threshold, and estimate the critical exponents $\alpha$, $\beta$, and $\gamma$ associated with the specific heat, order parameter, and susceptibility, respectively. The exponents vary continuously with $q$, reflecting a family of distinct universality classes as the global dimension of the
lattice depends on $q$. Remarkably, the Rushbrooke inequality, $\alpha + 2\beta + \gamma \ge 2$, is satisfied in near equality. Notably, the nonporous case ($q=1$) has a global dimension $2$ but lies outside the universality class of conventional two-dimensional
lattices. Our results highlight how
geometric disorder, multifractality, scale-free coordination number disorder, and porosity produce unconventional critical behavior.
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Materials Science
Non-Markovian heat production in ultrafast phonon dynamics
Fredrik Erikssonm Yulong Qiao, Erik Fransson, R. Matthias Geilhufe et al. (+1 more)
High-intensity THz
laser pulses enable the light-mediated control of
lattice vibrations by resonantly driving selected
phonon modes. On ultrafast timescales,
memory effects influence the
phonon dynamics and must be accounted for to describe the heat production associated with energy dissipation. Here, we establish a microscopic framework for non-Markovian
phonon dynamics by deriving the noise and dissipation kernels governing a driven
phonon mode. Using large-scale molecular dynamics simulations, we reconstruct these kernels directly from the many-body
lattice dynamics and determine the corresponding heat production rate. Our results provide a quantitative picture of the crossover between Markovian and non-Markovian dynamics on picosecond timescales and show how the finite bandwidth of the driving field limits the dynamically relevant bath spectrum. Furthermore, we demonstrate that thermodynamic quantities such as heat production can be inferred directly from the dynamics of an individual
phonon mode, enabling their experimental measurement using time-resolved spectroscopy.
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All authors Fredrik Erikssonm Yulong Qiao, Erik Fransson, R. Matthias Geilhufe, Paul Erhart
Mesoscale and Nanoscale Physics
Quantum metric senses a persistent spin helix
Awadhesh Narayan
Persistent
spin helices are a manifestation of
symmetry-protected
spin textures in systems with balanced
spin-orbit coupling. They enable long-lived
spin structures that are of interest for spintronics and coherent
spin manipulation. The
quantum metric has recently emerged as a promising tool for characterizing the
geometric structure of
quantum states. Here, we demonstrate that the
quantum metric provides a sensitive
geometric probe of the persistent
spin helix. Within the Rashba-Dresselhaus
Hamiltonian, we analytically evaluate the
quantum metric components and uncover a divergent
geometric contribution that emerges precisely at the persistent
spin helix condition. We reveal that this divergence originates from a hidden line degeneracy that forms when the strengths of Rashba and Dresselhaus
spin-orbit coupling become equal. We further study the role of higher-order cubic
spin-orbit interactions and determine how these corrections regularize the
geometric response and control the scaling behavior of the
quantum metric. Our results establish
quantum geometry as a powerful framework for identifying and characterizing persistent
spin helices and related
symmetry-protected
spin textures.
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Materials Science
Melting behavior and dynamical properties of Cr2Ge2Te6 phase-change material
Suyang Sun, Yihui Jiang, Riccardo Mazzarello et al. (+1 more)
Cr2Ge2Te6 (CrGT) is known as an intrinsic
ferromagnetic semiconductor and a promising candidate for phase-change
memory applications. In amorphous CrGT, Cr atoms form non-defective octahedral motifs with Te atoms, similar to those in the crystalline phase. The abundance of Cr[Te6] octahedra is regarded as the key structural factor in reducing the resistance drift coefficient of amorphous CrGT. However, the stage at which these octahedra emerge during melt-quench amorphization remains unclear. Here, we present ab initio molecular dynamics (AIMD) simulations to model the melting process of crystalline CrGT and to investigate the dynamical properties of
liquid and supercooled
liquid CrGT in detail. Upon heating, Ge atoms are observed to leave their
lattice sites earlier than Cr and Te atoms, diffusing into the van der Waals gap and initiating the collapse of the layered structure. The Cr[Te6] octahedra are more robust, maintaining their structural pattern up to 1400 K despite continuous rupture and re-formation of Cr-Te bonds. At higher temperatures, Cr and Te atoms start to migrate independently. In supercooled
liquid CrGT at 550 K, most Cr-centered octahedra remain intact, with only limited Cr-Te bond breaking. The collective motion of these octahedra in this temperature regime helps explain why crystallization in CrGT devices can be accomplished in tens of nanoseconds.
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All authors Suyang Sun, Yihui Jiang, Riccardo Mazzarello, Wei Zhang
Quantum Gases · Cross-listed from physics.atom-ph
Enhanced Rydberg Blockade through RF-tuned Förster Resonance
Lukas Palm, Bowen Li, Yiming Cady Feng et al. (+2 more)
Enhancing interactions between Rydberg atoms is a key challenge in contemporary
quantum technologies. Stronger interactions enable faster Rydberg gates in digital processors and larger entangled states in analog simulation. Achieving the same interaction strength at lower principal
quantum number addresses current constraints in available Rabi frequency and field sensitivity in large scale tweezer or cavity QED experiments. Here, we demonstrate a new technique using AC Stark shifts from a microwave drive to tune into a Förster resonance, thereby modifying the interaction scaling with distance from $1/R^6$ to $1/R^3$. We validate enhanced Rydberg interactions (in strength and range) by probing cavity Rydberg polariton blockade at $n=44$ in $^{87}$Rb, improving from $g^{(2)}(0) = 1.0 (1)$ in the Van-der-Waals regime to $g^{(2)}(0) = 0.38 (1)$ in the dipolar regime on the Förster resonance. Importantly, our technique allows minimal shifts of the original Rydberg state, suppressing detuning errors in gate protocols while maintaining quadratic insensitivity to DC electric fields.
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All authors Lukas Palm, Bowen Li, Yiming Cady Feng, Marius Jürgensen, Jon Simon
Strongly Correlated Electrons
Terahertz-nanoscale visualization of the microscopic spin-charge architecture of colossal magnetoresistive switching
Samuel Haeuser, Randall K. Chan, Richard H. J. Kim et al. (+4 more)
Resolving sub-10 nm
spin switching and the associated terahertz (THz) electrodynamics during the colossal magnetoresistance (CMR) transition is a definitive frontier in reaching the fundamental spatial, temporal, and energy-dissipation limits of
spin-based microelectronics and
quantum logic architectures. Yet, the requirement of simultaneous control of high
magnetic field, cryogenic environment, and nanometer-scale resolution has remained an elusive
benchmark for terahertz nanoscopy, leaving the obscured nano-scale high-frequency dynamics of these transitions largely unexplored. Here, we overcome these limitations by utilizing a custom-built cryogenic magneto-THz scattering-type scanning near-field optical microscopy (cm-THz-sSNOM) platform to resolve the nanoscale, THz spectroscopic
evolution of the
magnetic field-driven CMR transition in a manganite single
crystal $\text{Pr}_{2/3}\text{Ca}_{1/3}\text{MnO}_{3}$. Our measurements provide a real-space visualization of the local THz conductivity, capturing the moment that
magnetic-field-induced
spin switching triggers the phase transition from an
antiferromagnetic insulator to a
ferromagnetic metal. THz nano-imaging, together with an ellipsoidal near-field model, reveals a multi-scale transition initiated by 1-2 nm isolated
spin-flip sites at low
magnetic fields, which coalesce into $\sim$15~nm conducting regions as the threshold field is approached. These results provide an in situ, previously inaccessible THz real-space view of CMR switching, establishing a general analysis framework for mapping
spin-charge-
lattice-orbit-coupled dynamics at spatial scales that transcend the nominal sSNOM resolution.
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All authors Samuel Haeuser, Randall K. Chan, Richard H. J. Kim, Joong-Mok Park, Martin Mootz, Thomas Koschny, Jigang Wang
Materials Science
First-principles identification of optically efficient erbium centers in GaAs
Khang Hoang
Gallium arsenide (GaAs) doped with erbium (Er), a material of interest for optoelectronics and
quantum information, has been studied for decades. Yet the formation of Er luminescence centers in the
semiconductor host and their properties are still not well understood. Here we present a systematic investigation of Er-related defects in GaAs, including defect complexes consisting of Er and native point defects or oxygen
impurities, using first-principles hybrid-functional defect calculations. We find that these defects have electronic structure and energetics that are generally asymmetric with respect to n- and p-type doping and tend to favor electron trapping. On the basis of the calculated defect levels, formation energies, and nonradiative carrier capture coefficients, we identify Er-related defects that are efficient as trap-assisted nonradiative recombination centers for Er$^{3+}$ excitation under host photoexcitation or via minority carrier injection. Our results provide an understanding for why a particular defect center with Er coupled to two oxygen atoms is most efficient, and for the effects of n- and p-type doping and of the Er/O ratio on the formation of optically active Er centers and on the Er luminescence observed in experiments.
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Mesoscale and Nanoscale Physics
Band modulations and topological transitions in a one-dimensional periodic bead-on-string chain
Haocong Pan, Wei Wang and Chunling Liu
We study band modulations and topological transitions in a one-dimensional periodic bead-on-string chain. Using an exact transfer-
matrix formulation of the wave equation with periodically modulated mass density, combined with numerical spectral searches and tabletop experiments, we characterize band gaps and localized midgap states. We interpret these states by mapping the system to the Su-Schrieffer-Heeger (SSH) model and its low-energy (1+1)-dimensional Dirac theory. This framework reveals that the robust states are topological
solitons bound to boundaries or engineered domain walls in the Dirac mass. Through this mapping, we provide an intuitive account of how band structure controls topological phase changes in mechanically realizable
lattices.
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Other Condensed Matter · Cross-listed from quant-ph
Symmetric Trotterization in digital quantum simulation of quantum spin dynamics
Yeonghun Lee
A higher-order Suzuki-Trotter decomposition or Trotterization can be exploited to mitigate the Trotter error in digital
quantum simulation. This work revisits the second-order symmetric Trotterization in terms of the Trotter error, where
quantum many-body
spin dynamics of the transverse-field Ising model is simulated. While the work presents a pedagogical way to exploit a real
quantum computer, the effectiveness of the symmetric Trotterization is evaluated in a prototype superconducting
quantum device on IBM
Quantum Experience. It turns out that the symmetric Trotterization does not provide higher accuracy than the first-order Trotterization in the testbed using the transverse-field Ising model. The result indicates that apart from the
quantum errors, such as logical gate error and readout error, the use of a higher-order Trotterization should be circumspect, and the Trotter error would play an insignificant role in particular applications in an early stage of realized noisy intermediate-scale
quantum (NISQ) devices.
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Mesoscale and Nanoscale Physics
Designing Extremely Low-Power Topological Transistors with 1T'-MoS2 and HZO for Cryogenic Applications
Yosep Park, Yungyeong Park, Hyeonseok Choi et al. (+2 more)
Large-scale
quantum computing requires cryogenic electronic controllers such as control/readout
circuit and routing
circuit. However, current technologies face high power dissipation problems, hindering large-scale
qubit integration. Here, we theoretically propose extremely low-power cryogenic topological transistors, i.e., negative-capacitance topological
insulator field-effect transistors (NC-TIFETs). By combining a gate-field-induced two-dimensional 1T'-Molybdenum Disulfide (MoS$_2$) topological channel with a hafnium-zirconium
oxide (HZO) ferroelectric gate
insulator, NC-TIFETs exhibit an extremely steep-slope transfer curve and ultra-high transconductance at low drain voltage ($V_{\mathrm{D}}$). Therefore, NC-TIFETs are the compelling candidate for minimizing power dissipation in the cryogenic electronic interfaces essential for large-scale
quantum computing systems.
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All authors Yosep Park, Yungyeong Park, Hyeonseok Choi, Subeen Lim, Yeonghun Lee
Mesoscale and Nanoscale Physics · Cross-listed from physics.optics
Explicit Construction of Floquet-Bloch States from Arbitrary Solution Bases of the Hill Equation
Gregory V Morozov
For the Hill equation describing one-dimensional periodic systems, a constructive formulation is developed for generating Floquet-Bloch states directly from arbitrary pairs of linearly independent solutions. One-dimensional photonic
crystals are used as a concrete illustration. Explicit closed-form formulas map an arbitrary fundamental system to the corresponding Floquet-Bloch basis via the monodromy
matrix, including the generic Jordan band-edge case, without reliance on canonically normalized solutions. The construction can be expressed directly in terms of the transfer
matrix, making the residual representation freedom transparent and providing an implementation-ready framework for analytical and numerical studies of periodic systems.
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