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Physics Condensed Matter

cond-mat Watch Condensed Matter

Wednesday 8 April

Strongly Correlated Electrons

Magnon harmonic generation in antiferromagnets: Dynamical symmetry enriched by symmetry breaking

Yuto Jita, Minoru Kanega, Takumi Ogawa et al. (+2 more)

In recent years, techniques of intense THz laser have enabled us to experimentally observe nonlinear spin dynamics in antiferromagnets since the elementary excitations such as magnons reside on a THz to GHz range in antiferromagnets and THz laser thus can directly excite them. We numerically and theoretically investigate THz-laser or GHz-wave driven harmonic generations in typical ordered phases of antiferromagnets: Néel, canted and weak ferromagnetic phases. The radiation waves (harmonic generations) are created by the incident-wave driven magnon dynamics. We point out that magnetic orders and phase transitions can change the spectra of harmonic generations, differently from those of metallic, semiconductor, or atomic-gas systems without (spontaneous) symmetry breakings. We consider both the magnon harmonic generation driven by standard single-color laser and that by two-color laser in the antiferromagnets, and find several dynamical symmetries and the corresponding selection rules of the harmonic generations. These results indicate that the magnon harmonic generation spectra provide new information about symmetry or symmetry breaking of antiferromagnets.
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All authors Yuto Jita, Minoru Kanega, Takumi Ogawa, Shunsuke C. Furuya, Masahiro Sato

Soft Condensed Matter

Cholesteric Fingers from a Magnetic Perspective: Topology, Energetics, and Interactions

Takayuki Shigenaga and Andrey O. Leonov

Chiral liquid crystals and chiral magnets host a wide variety of topological solitons described by closely related continuum theories, namely the Frank-Oseen and Dzyaloshinskii models. Exploiting this correspondence, we develop a unified description of cholesteric fingers in confined liquid crystals and their magnetic counterparts. Within a continuum framework including bulk and surface anisotropies, we analyze the topology, structure, interactions, and collective states of the two main finger types, CF-1 and CF-2. We show that cholesteric fingers are composite chiral solitons built from merons. CF-2 corresponds to a bimeron with unit topological charge, while CF-1 is a topologically trivial composite of two merons with identical vorticities. From a homotopic viewpoint these textures correspond to skyrmions and droplets. Strong homeotropic anchoring induces confinement effects that reshape the meron structure and redistribute topological charge across the film thickness. Isolated fingers in the homogeneous state interact repulsively and behave as particle-like objects. Periodic phases emerge when the energy of an isolated finger becomes negative, leading to nucleation-type transitions with a diverging lattice period. Degenerate finger types allow mixed periodic sequences, analogous to stacking polytypes. In a conical background, interactions become attractive due to overlap of distortion regions. Film thickness controls stability and structure: at small thickness solitons collapse, while at large thickness bimerons exhibit bistability between surface-stabilized and bulk-like states.
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Materials Science

High-Mobility Indium Native Oxide Transistors via Liquid-Metal Printing in Air

Shi-Rui Zhang, Sanjoy Kumar Nandi, Felipe Kremer et al. (+8 more)

Oxide semiconductors have emerged as common channel materials in transistors and hold promise for next-generation electronics, yet achieving high mobility typically requires costly vacuum-based techniques. Here, ultrathin (5-nm) indium native oxide (InOx) prepared by ambient-air liquid-metal printing (LMP) at low temperature (250 {\deg}C), is applied as semiconducting channel in field-effect transistor (FET). The resulting InOx is found to be polycrystalline with large lateral grains that extend vertically throughout the film thickness. InOx FETs in a transfer length method (TLM) configuration demonstrate a high conductivity mobility (uCON) of 125 cm2 V-1 s-1, with systematic analysis of contact resistance confirming potential for channel length scaling. Integration with atomic-layer-deposited (ALD) gate dielectrics further reveals excellent compatibility, for instance, InOx FET integrated with HfO2 exhibits a high field-effect mobility (uFE) of 107 cm2 V-1 s-1, an on/off current ratio (ION/IOFF) of >107, a subthreshold swing (SS) of 204 mV dec-1, a gate leakage of <10-6 A cm-2, while maintaining stable performance over 104 endurance cycles without degradation. Post-fabrication oxygen-plasma treatment is applied to achieve enhancement-mode operation and a depletion-load inverter is demonstrated, exhibiting a voltage gain of 69.8 V/V. These results demonstrate the great potential of LMP InOx as semiconducting channel in high-performance and power-efficient transistors for next-generation oxide electronics.
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All authors Shi-Rui Zhang, Sanjoy Kumar Nandi, Felipe Kremer, Shimul Kanti Nath, Wenzhong Ji, Thomas Ratcliff, Li Li, Nicholas J. Ekins-Daukes, Teng Lu, Yun Liu, Robert Glen Elliman

Strongly Correlated Electrons

Investigating the intrinsic anomalous Hall effect in MnPt3 topological semimetal

Jing Meng, Hongru Wang, Kun Zheng et al. (+15 more)

The cubic Cu$_3$Au-type $X$Pt$_3$ family ($X$ = V, Cr, and Mn) is a topological semimetal characterized by anti-crossing gapped nodal lines near the Fermi level, which give rise to significant Berry curvatures and thus to the anomalous Hall effect (AHE). Among the three members, CrPt$_3$ has been experimentally verified to exhibit a large anomalous Hall conductivity (AHC), while its counterparts MnPt$_3$ and VPt$_3$ remain largely unexplored. Here, a series of MnPt$_3$ thin films with varying thicknesses (20–70 nm) was epitaxially grown on the MgO substrates using magnetron sputtering and was systematically investigated by magnetization, electrical resistivity, and Hall resistivity measurements. MnPt$_3$ films undergo a ferromagnetic transition at a Curie temperature $T_\mathrm{C}$, which increases as the film thickness increases, reaching $\sim$ 344 K for the 70-nm-thick film. All the anomalous Hall transport properties of MnPt$_3$ films, including the resistivity, conductivity, and angle, exhibit a strong correlation with their magnetic properties. The scaling analysis suggests that the intrinsic Berry-curvature mechanism dominates the observed AHE, while the extrinsic contributions are much smaller. The intrinsic AHC increases as the film thickness increases, while the extrinsic AHC is thickness-independent. Such an enhanced intrinsic AHC in the MnPt$_3$ films is most likely attributed to the strain effect, implying that it serves as an effective method to tune the electronic band topology in the $X$Pt$_3$ topological semimetal.
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All authors Jing Meng, Hongru Wang, Kun Zheng, Yuhao Wang, Zheng Li, Bocheng Yu, Haoyu Lin, Keqi Xia, Jingzhong Luo, Zengyao Wang, Xiaoyan Zhu, Baiqing Lv, Yaobo Huang, Jie Ma, Yang Xu, Shijing Gong, Tian Shang, Qingfeng Zhan

Quantum Gases

Breathing Modes as a Probe of Energy Fluctuations in a Unitary Fermi Gas

Shi-Guo Peng, Jing Min and Kaijun Jiang

Directly accessing energy fluctuations in interacting quantum many-body systems remains a long-standing challenge, especially far from equilibrium. Here we show that in scale-invariant quantum gases with SO$(2,1)$ dynamical symmetry, the amplitude of the breathing mode provides a direct and quantitative probe of energy fluctuations. We establish an exact and universal relation between the oscillation amplitude and the energy fluctuation, with a dimensionless ratio fixed solely by the Bargmann index $k$, which labels the irreducible representation of the underlying SU$(1,1)$ algebra and thereby determines the structure of the many-body spectrum and dynamics. As a consequence, this relation is fully dictated by symmetry and remains independent of microscopic details and excitation protocols. Furthermore, we show that the excitation of breathing-mode states follows a universal statistical distribution governed by a single parameter, independent of the specific driving protocol. Our findings demonstrate that energy fluctuations, typically encoded in the many-body spectrum, can be directly accessed through collective dynamics, offering a symmetry-based route to probe nonequilibrium energy statistics in strongly interacting quantum systems.
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Strongly Correlated Electrons

Decomposing momentum scales in the Hubbard Model: From Hatsugai-Kohmoto to Aubry-André

Dmitry Manning-Coe and Barry Bradlyn

The all-to-all momentum coupling of the Hubbard interaction makes interacting lattice models generically unsolvable. In many settings, however, from Peierls instabilities to Moiré superlattice physics, the low-energy behavior is dominated by scattering at a few characteristic wavevectors. We exploit this by constructing a momentum-space clustering scheme that retains only a chosen subset of interaction channels. Our scheme can be considered a generalization of twist-averaged boundary conditions. In proving this, we also prove that our scheme can be considered as a generalization of Hatsugai-Kohmoto (HK) models, and all versions of the HK model previously considered in the literature arise as special cases. This shows that the surprising phenomenological success of HK models arises from their correspondence to the finite-site Hubbard model. In particular, the recently introduced "Momentum-Mixing HK" model corresponds to a specific choice of clustering limit, which is equal to the original finite-site Hubbard model with twist-averaged boundary conditions. Our scheme becomes particularly powerful when a spatially varying potential selects the dominant momentum channels. We demonstrate this on the one-dimensional analogue of interacting moiré systems: the Aubry-André-Hubbard model. We show that for sufficiently strong onsite potential, clusters as small as two sites can recover the ground state energy to below 1% error relative to DMRG benchmarks. This establishes that physically motivated momentum-space truncations can yield accurate low-energy descriptions at feasible computational cost, opening a path toward tractable interacting models of Moiré systems in two dimensions. Code for reproducing all numerical results is available at https://github.com/chainik1125/decomposing-hubbard.
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Materials Science

On the possibility of hybrid chalcogenide perovskite photovoltaics

Ruiqi Wu, JJ Acton, Shirui Wang et al. (+1 more)

Chalcogenide perovskites are an emerging class of photovoltaic absorbers offering stable, lead-free structures and promising optoelectronic properties. To date, the literature on chalcogenide perovskites has focused primarily on fully inorganic systems such as \ce{BaZrS3}. This contrasts with the halide perovskites, for which hybrid organic-inorganic systems exhibit record performance. In this work, we assess the viability of hybrid chalcogenide perovskite absorbers using first-principles calculations. We screen a wide range of monovalent and divalent organic cations within the A-site to evaluate their electronic, optical, and thermodynamic properties. Our analysis reveals that the majority of candidates are structurally unstable; however, we identify the hydrazinium cation (\ce{N2H6^{2+}}) as a unique candidate that maintains a stable perovskite structure. Specifically, we identify \ce{N2H6ZrSe3} as the most promising candidate, exhibiting a quasi-direct band gap of \SI{1.31}{eV} and a theoretical maximum efficiency of \SI{24.5}{\percent} for a \SI{200}{\nm} thin film. This study represents the first comprehensive computational report on hybrid chalcogenide perovskites, opening new avenues for the development of Earth-abundant photovoltaic materials.
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All authors Ruiqi Wu, JJ Acton, Shirui Wang, Alex Ganose

Statistical Mechanics · Cross-listed from math.AP

Local H theorem for Enskog and Enskog-Vlasov equations with a modified Enskog factor

Aoto Takahashi and Shigeru Takata

The local H theorem is shown to hold for the Enskog equation with a modified Enskog factor proposed by the authors [Phys. Rev. E 111, 065108 (2025)]. This is a stronger statement than the global one in the same paper and has been obtained along the lines of Mareschal et al. [Phys. Rev. Lett. 52, 1169-1172 (1984)] for the modified (or revised) Enskog equation. Furthermore, it is shown that the local H theorem also holds for the corresponding Enskog-Vlasov equation.
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Materials Science

The effects of dispersion damping and three-body interactions for accurate layered-material exfoliation energies

Adrian F. Rumson, Kyle R. Bryenton and Erin R. Johnson

Accurate predictions of exfoliation energies and lattice constants of layered materials hinge on a correct description of London dispersion physics. Modern a posteriori dispersion corrections in density-functional theory (DFT), such as the exchange-hole dipole moment (XDM) model, capture the proper asymptotic behaviour at long range while making use of damping functions to prevent unphysical divergence at short range. In the united-atom limit, the dispersion energy is damped to a finite, non-zero value by both the canonical Becke–Johnson (BJ) damping function and the new Z-damping function. XDM(BJ) has previously demonstrated exceptional accuracy for modelling layered materials, such as in the LM26 benchmark, which includes graphite, hexagonal boron nitride, lead(II) oxide, and transition-metal dichalcogenides. This work presents the first assessment of XDM(Z) on the same benchmark. We also show that inclusion of three-body interactions via the Axilrod–Teller–Muto (ATM) term further improves the computed exfoliation energies for both XDM(BJ) and XDM(Z), yielding the best performance achieved on LM26 using semi-local functionals to date, relative to reference data from the random-phase approximation.
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Tuesday 7 April

Other Condensed Matter · Cross-listed from physics.soc-ph

Financial Interactions and Collective States: Part III. Description of Dynamic Collective States

Pierre Gosselin and Aïleen Lotz

In a series of papers, we analyzed the mechanisms of capital allocation and accumulation among firms, investors, and banks within the framework of Field Economics. At the macro level, we found that multiple collective states may emerge, each organized in groups of agents characterized by distinct levels of disposable capital, returns, and stakes across sectors. This multiplicity of collective states reflects the inherent instability and default-prone nature of financial markets. It also underscores the necessity of transitions among these states. These transitions were not fully accounted for in our previous description of collective states, where we only considered marginal fluctuations around equilibrium levels. To fill this gap, the present paper aims to characterize the possible dynamic mechanisms underlying transitions between these collective states. It reviews and extends our previous analysis by examining their probability and stability. By introducing the notion of dynamic sub-collective states, it explores potential patterns of transition-such as morphing, merging, or splitting-among collective states. This study thus provides the foundational tools and analytical framework that will be employed to develop a field-theoretic description of dynamic collective states.
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Materials Science · Cross-listed from physics.bio-ph

Drug-delivery Ca-Mg silicate scaffolds encapsulated in PLGA

A. Jadidi, E. Salahinejad, E. Sharifi et al. (+1 more)

The aim of this work is to develop dual-functional scaffolds for bone tissue regeneration and local antibiotic delivery applications. In this respect, bioresorbable bredigite (Ca7MgSi4O16) porous scaffolds were fabricated by a foam replica method, loaded with vancomycin hydrochloride and encapsulated in poly lactic-co-glycolic acid (PLGA) coatings. Field emission scanning electron microscopy, Archimedes porosimetry and Fourier-transform infrared spectroscopy were used to characterize the structure of the scaffolds. The drug delivery kinetics and cytocompatibility of the prepared scaffolds were also studied in vitro. The bare sample exhibited a burst release of vancomycin and low biocompatibility with respect to dental pulp stem cells based on the MTT assay due to the fast bioresorption of bredigite. While keeping the desirable characteristics of pores for tissue engineering, the biodegradable PLGA coatings modified the drug release kinetics, buffered physiological pH and hence improved the cell viability of the vancomycin-loaded scaffolds considerably.
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All authors A. Jadidi, E. Salahinejad, E. Sharifi, L. Tayebi

Materials Science · Cross-listed from physics.bio-ph

Competition of carrier bioresorption and drug release kinetics of vancomycin-loaded silicate macroporous microspheres to determine cell biocompatibility

A. Bolandparvaz Jahromi and E. Salahinejad

Bioceramic porous microspheres are promising substances for dental and orthopedic bone void filling, tissue engineering and drug delivery applications. In this research, the structure and cytocompatibility of bioactive magnesium-calcium silicate macroporous microspheres loaded with vancomycin hydrochloride, an antibiotic drug, were studied. In this regard, bredigite (Ca7MgSi4O16), akermanite (Ca2MgSi2O7) and diopside (CaMgSi2O6) carriers were fabricated through a sequence of sol-gel, calcination, droplet extrusion and sintering processes, followed by impregnated with vancomycin. X-ray diffraction (XRD) and scanning electron microscopy verified the formation of the desired ceramic crystalline phases and macroporous characteristics of the carriers, respectively. Based on the MTT assay, the antibiotic-loaded bredigite, akermanite and diopside devices comparatively exhibited the lowest, intermediate and highest levels of human bone marrow mesenchymal stem cells (hBM-MSCs) viability and proliferation, respectively. It was concluded that the role of the carrier bioresorption kinetics prevails over the drug delivery kinetics in determining the cell biocompatibility of the devices.
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Statistical Mechanics

Comment on "Extension of the adiabatic theorem"

Jie Gu

Phys. Rev. B 113, 165102 (2026) proposed the conjecture that, for quantum quenches within the same phase, the overlap between the initial ground state and postquench eigenstates is maximal for the postquench ground state. We show that this conjecture is not valid in general. An explicit local, translationally invariant, gapped free-fermion counterexample exists even though the pre- and postquench Hamiltonians are connected by a symmetry-preserving gapped path and the thermodynamic-limit spectrum is continuous.
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Soft Condensed Matter

i-Rheo-Tempo: A Model-Free, Quadrature-Free Reconstruction of the Shear Relaxation Modulus from Complex Viscosity

Jorge Ramírez and Manlio Tassieri

Reliable transformation between frequency- and time-domain material functions remains a central challenge in linear viscoelasticity due to finite bandwidth, discrete sampling, and experimental noise. We introduce \emph{i\text{-}Rheo-Tempo}, a quadrature-free method that reconstructs the shear relaxation modulus directly from dynamic measurements through an exact second-derivative representation of the complex viscosity. When the spectrum is approximated as piecewise linear, the inversion reduces to a compact interval-slope formulation based solely on local spectral properties, avoiding numerical quadrature, parametric fitting, and predefined relaxation spectra. The method is validated against a set of complex fluids including synthetic models, polymer melts, industrial elastomers, comb polymers, and broadband microrheology datasets spanning nearly nine decades in frequency. In all cases, the reconstructed relaxation modulus is in quantitative agreement with independent time-domain measurements. These results demonstrate that \emph{i\text{-}Rheo-Tempo} provides a robust, model-free solution to the frequency-to-time inverse problem and, more generally, establishes a framework for recovering time-domain responses from experimentally measured complex spectra.
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Strongly Correlated Electrons

K$_2$Co$_2$(TeO$_{3}$)$_{3}$ $\cdot$ 2.5 H$_2$O : A mineral-inspired pseudo-honeycomb cobalt dimer antiferromagnet

Austin M. Ferrenti, Maxime A. Siegler, Yiqing Hao et al. (+9 more)

In recent years, magnetically-frustrated triangular and honeycomb lattice cobaltates have seen extensive study in the pursuit of a quantum spin liquid (QSL) state in a real material. In this work, we describe the hydroflux synthesis of K$_2$Co$_2$(TeO$_{3}$)$_{3}$ $\cdot$ 2.5 H$_2$O (KCoTOH), a novel zemannite-type antiferromagnet (AFM) possessing structural elements of both triangular dimer and honeycomb structural motifs. Bulk magnetometry and specific heat data support the onset of long-range AFM order below $T_\text{N}$ = 7.6(1) K, with neutron diffraction and muon spin relaxation ($\mu$SR) measurements placing the majority of the ordered moment within the pseudo-honeycomb plane. We resolve three unique oscillation frequencies from the zero-field $\mu$SR spectra, additionally suggesting a remarkably low level of structural disorder in as-grown KCoTOH crystals. Whereas interactions between dimerized chains of Co$^{2+}$ cations are typically observed to be negligible or ferromagnetic in nature, the largely planar ordering motif observed in KCoTOH is instead stabilized by net antiferromagnetic interactions through bridging tellurite groups. This work highlights the potential of hydroflux synthesis methods in the stabilization of magnetic materials possessing novel and potentially more frustrated lattice geometries.
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All authors Austin M. Ferrenti, Maxime A. Siegler, Yiqing Hao, Chris Lygouras, Tong Chen, Tiffany A. Soetojo, Megan R. Rutherford, Kenji M. Kojima, Huibo Cao, Natalia Drichko, Alannah M. Hallas, Tyrel M. McQueen

Quantum Gases · Cross-listed from physics.flu-dyn

Collective Dynamics of Vortex Clusters in Compact Fluid Domains: From Pair Interactions to a Quadrupole Description

Aswathy KR and Rickmoy Samanta

Clusters of co-rotating vortices on compact fluid domains exhibit a simple collective dynamics, combining coherent global rotation with a slow breathing of the cluster size. In this work, we investigate an analytic model of vortex interactions on a doubly periodic inviscid fluid domain, based on an exact representation in terms of the Schottky-Klein prime function and its $q$-representation. The two-vortex problem reduces to a single complex degree of freedom, from which explicit expressions for the orbital rotation frequency and dipole translation velocity are obtained. Building on this framework, we derive a small-cluster expansion that reveals a decomposition of the dynamics into universal planar interactions, isotropic torus corrections, and geometry-induced anisotropic modes. At leading order, the collective dynamics is encoded in a single complex quadrupole moment: its real part governs corrections to the rotation rate, while its imaginary part controls the slow breathing of the cluster. These predictions are quantitatively confirmed by direct numerical simulations, establishing a reduced description of vortex clusters on the flat torus and compact fluid domains.
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Materials Science

Quantitative 3D Analysis of Porosity and Fractal Geometry in Electrochemically Etched Macroporous Silicon

A. Ramírez-Porras, I. Prado, N.R. Schwarz et al. (+1 more)

Macroporous silicon is widely employed in sensing and optoelectronic applications due to its large internal surface area and adjustable pore structure. However, quantitative correlations between morphology and functionality require accurately characterizing the three dimensional pore network. In this study, we used focused Ga+ ion beam scanning electron microscopy tomography to reconstruct representative volumes of electrochemically etched macroporous silicon layers. We extracted true three dimensional porosity and surface-to-volume ratios and compared them with two-dimensional estimates obtained from SEM images. Our results demonstrate that surface-based porosity systematically underestimates true volumetric porosity. These discrepancies arise from anisotropy, branching, and variability in pore size. Fractal analysis reveals that the pore network has moderate geometric complexity, consistent with electrochemical macropore formation mechanisms. The results highlight the importance of direct 3D characterization for reliable morphological quantification and provide a robust framework for interpreting structural trends in macroporous silicon.
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All authors A. Ramírez-Porras, I. Prado, N.R. Schwarz, U. Steiner

Quantum Gases

Observation of roton emission from a quantized vortex

A. Lester, N. Morrison, F. Novotny et al. (+5 more)

Turbulence in inviscid quantum fluids offers unparalleled access to the universal principles of non-equilibrium dynamics, spanning a vast range of length scales from macroscopic flow down to the individual vortex core. In the zero-temperature limit, the microscopic mechanism by which the turbulent energy cascade terminates in the absence of viscosity remains a foundational challenge in quantum hydrodynamics. While prevailing theoretical descriptions prioritize phonon emission, they fail to account for the strong interatomic correlations that give rise to the roton minimum in superfluid $^4\mathrm{He}$. Here, we report the direct observation of roton emission from a single quantized vortex using a high-quality-factor nanomechanical resonator at 10 mK. We identify a sharp onset of dissipation at a critical velocity, and measure the energy loss per cycle, which corresponds quantitatively to the roton gap energy. Our findings address the long-standing mystery of zero-temperature energy relaxation by establishing roton emission as the primary dissipation channel in strongly correlated quantum liquids.
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All authors A. Lester, N. Morrison, F. Novotny, D. Schmoranzer, S.Ó Peatáin, V. Zavjalov, V. Tsepelin, S. Kafanov

Strongly Correlated Electrons

Floquet X-Ray Scattering as a Probe of Hidden Electronic Orders

Martin Eckstein and Eva Paprotzki

We develop a theoretical framework for Floquet resonant X-ray scattering, using Floquet theory combined with the ultrashort core-hole lifetime expansion. We obtain a compact expression for the Floquet components of the resonant inelastic X-ray scattering operator, which shows that Floquet X-ray scattering provides direct access to bond and current correlations that do not directly produce charge Bragg peaks in conventional diffraction. Applying this framework to charge-ordered states on the Kagome lattice, we demonstrate that different symmetry-breaking orders exhibit distinct polarization fingerprints in the Floquet Bragg peaks. Moreover, the relative weight of bond and current contributions can be tuned through the drive frequency. These results establish Floquet X-ray scattering as a symmetry-resolved probe of hidden electronic order or fluctuations in quantum materials.
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Mesoscale and Nanoscale Physics

Ballistic atomic transport in narrow carbon nanotubes

Alberto Ambrosetti, Pier Luigi Silvestrelli, John F. Dobson et al. (+1 more)

Friction forces are conventionally modeled via semiclassical theories that associate energy dissipation with newtonian motion on corrugated interface potentials. This consolidated approach is challenged at the nanoscale by observation of nearly unimpeded water flow in narrow carbon nanotubes (CNTs), in spite of nonvanishing energy corrugations. Here we go beyond the standard newtonian perspective, adopting a quantum mechanical description of 4 He flow through narrow CNTs. Building upon our Bloch-wave dynamics [Phys. Rev. Lett. 131, 206301 (2023)] we explore realistic flow conditions, including non-negligible interface interactions, finite temperatures, and imperfect CNTs. At T = 0 K we found that 4 He waves can propagate through ideally periodic, corrugated interface potentials with no friction: below a critical velocity regulated by interface corrugations, energy loss by emission of plasmon and phonon quanta is forbidden. Introducing realistic impurities/defects one still finds very large mean free paths that can exceed the micrometer scale, while thermal phonons and plasmons yield even lower scattering rates. This establishes the unexpected emergence of ballistic wavelike transport in narrow CNTs within realistic nanoscale devices, and demonstrates the intrinsic quantumness of nanoscale interfaces.
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All authors Alberto Ambrosetti, Pier Luigi Silvestrelli, John F. Dobson, Luca Salasnich

Statistical Mechanics

Dimensional crossover in surface growth on rectangular substrates

Ismael S. S. Carrasco and Tiago J. Oliveira

In a recent work [Phys. Rev. E 109, L042102 (2024)], interesting dimensional crossovers [from two- to one-dimensional (2D to 1D) scaling] were found in the growth of Kardar-Parisi-Zhang (KPZ) interfaces on rectangular substrates, with lateral sizes $L_y > L_x$. Here, we extend this study to other universality classes for interface growth – specifically, the Edwards-Wilkinson (EW), the Mullins-Herring (MH), and the Villain-Lai Das Sarma (VLDS) classes. From extensive simulations, we demonstrate that, in all systems with sufficiently large aspect ratio $\mathcal{R}=L_y/L_x$, the roughness $W$ scales with time $t$ in the growth regime as $W \sim t^{\beta_{\text{2D}}}$ for $t \ll t_c$ and $W \sim t^{\beta_{\text{1D}}}$ for $t \gg t_c$, where $t_c \sim L_x^{z_{2\text{D}}}$ in most cases. For the VLDS class, this crossover is also observed in the height distribution (HD), which approaches its characteristic probability density function for the 2D case at short times ($t \ll t_c$) and then crosses over to the asymptotic 1D HD. Dimensional crossovers are also found in the steady state regime, both in the roughness scaling as well as in the VLDS HD, which interpolate between the 2D and 1D ones as $\mathcal{R}$ increases. The particular case $L_x = L_y^{\delta}$, with $0 < \delta < 1$, is also discussed in detail and reveals interesting features of the investigated systems. For instance, there exist a `special' exponent $\delta^* = z_{1\text{D}}/z_{2\text{D}}$ such that the temporal crossover cannot be observed for $\delta > \delta^*$. Moreover, this leads the saturation roughness to display a nonuniversal scaling: $W_s \sim L_y^{\Lambda}$, with $\Lambda = (1-\delta) \alpha_{1\text{D}} + \delta \alpha_{2\text{D}}$.
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Materials Science · Cross-listed from physics.app-ph

Blue Organic Light-Emitting Diodes with External Quantum Efficiencies over 20% Based on Europium(II) Emitters

Mahmoud Soleimani, Toni Bärschneider, Felix Kaden et al. (+4 more)

The realization of blue electroluminescence with high efficiency and lifetime remains a long-standing hurdle for organic light-emitting diode (OLED) technology to overcome. Divalent Europium [Europium(II)] complexes offer a fundamentally distinct pathway toward this goal, as their atomic 4f-5d transitions yield single-Gaussian, spectrally pure emission with theoretical 100% exciton utilization in electroluminescence and no involvement of fragile organic bonds in the emissive process. Here, we present a rigid aza-crown europium(II) complex (Eu5NHCrown) that achieves near-unity photoluminescence quantum yield with bright, pure-blue emission and its incorporation in OLEDs. The emitter complex sublimes without decomposition and can be processed by industry-standard vacuum deposition. A bottom-emitting, single-host OLED architecture delivers an external quantum efficiency (EQE) of 20.7% with minimal roll-off (19.3% at 1000 cd m${}^{-2}$ ) and a narrowband electroluminescence with Commission Internationale de l'Eclairage (CIE) coordinates of (0.12, 0.25). This ligand design provides enhanced steric shielding of the Eu(II) center, enabling the highest reported efficiency among vacuum-deposited Eu(II)- based blue OLEDs while maintaining performance at high luminance. These results reveal the true potential of divalent Europium 4f-5d transitions for high-efficiency blue OLEDs, establishing a molecular design concept that bridges atomic-transition efficiency with the processability of organic materials.
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All authors Mahmoud Soleimani, Toni Bärschneider, Felix Kaden, Roman Tkachov, Sebastian Schellhammer, Sebastian Reineke, Carsten Rothe

Materials Science · Cross-listed from physics.app-ph

High-Efficiency Deep Blue Single-Gaussian Europium(II) Emitters and their Emitter-Host Interactions

Mahmoud Soleimani, Paulius Imbrasas, Jan-Michael Mewes et al. (+6 more)

Eu(II) complexes are attractive emitters for deep-blue organic light-emitting diodes (OLEDs) due to their narrow, parity-allowed 4f-5d emission; however, their implementation in vacuum-processed OLEDs has remained limited. Here, we introduce a new molecular design concept for Eu(II) emitters, in which a crown-ether ligand is combined with carborate anions to define the coordination environment and improve steric shielding of the europium center. Based on this design, we present two emitters that combine narrow deep-blue photoluminescence with quantum yields approaching 90% and sufficient thermal stability for vacuum deposition. As the excited state dynamics of this emitter class are different from most conventional OLED emitters and the pathway to maximum luminescence efficiency in thin films is not fully established, we study interactions between Eu(II) complexes and the host environment, based on density functional theory and time-resolved experiments. We identify steric shielding of the Eu(II) core and energetic confinement of the excited 5d electron, defined by molecular design as key factors governing efficient luminescence, providing a roadmap for rational design of Eu(II) emitters. Together, these results establish a basis for higher-efficiency and deeper blue OLEDs incorporating Eu(II) emitters.
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All authors Mahmoud Soleimani, Paulius Imbrasas, Jan-Michael Mewes, Felix Kaden, Stephanie Anna Buchholtz, Karl Leo, Sebastian Schellhammer, Carsten Rothe, Sebastian Reineke

Statistical Mechanics

Extensive Spatio-Temporal Chaos in Non-reciprocal Flocking

Chul-Ung Woo, Jae Dong Noh and Heiko Rieger

Non-reciprocal interactions in active matter give rise to a multitude of fascinating phenomena among which are collective oscillatory states without intrinsic particle chirality and active turbulence. Here we show that in a paradigmatic model for non-reciprocal flocking, the two species Vicsek model, these two states coexist: chiral order for small flocks, and extensive spatiotemporal chaos for large flocks, both separated by a finite-wavelength instability whose scale is set by the rotation radius of the chiral orbits. For system sizes larger than this length scale extensive spatiotemporal chaos unfolds, as manifested by an extensive number of positive Lyapunov exponents as well as of Floquet exponents, a finite correlation and chaotic length and a broad energy spectrum. Our results suggest that complex, turbulent behavior is a generic possibility in systems where particles or fields interact asymmetrically, and may have significant implications for understanding how non-reciprocal interactions could drive chaotic, fluid-like behavior in active matter.
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Statistical Mechanics · Cross-listed from quant-ph

Quantum Fragmentation

Yiqiu Han, Oliver Hart, Alexey Khudorozhkov et al. (+1 more)

We introduce a systematic protocol for constructing quantum Hilbert-space-fragmented Hamiltonians, whose Krylov-sector structure, unlike in classically fragmented models, can be fully resolved only in an entangled basis. The protocol takes as input a classically fragmented model and uses a Rokhsar-Kivelson type construction to promote it to a quantum fragmented model. Notably, the procedure also works with non-fragmented inputs (such as Ising models). We explain how the Krylov sectors of the resulting quantum fragmented model may be labeled and counted in one dimension, and outline experimentally accessible verification of quantum fragmentation, assuming the ability to prepare specific initial states and perform tomography on reduced density matrices. We further analyze the entanglement structure of the entangled basis underlying quantum fragmentation, which sharply distinguishes it from both classical fragmentation and the trivial "fragmentation" of generic Hamiltonians in their eigenbasis. We also extend the construction to higher dimensions, with an explicit proof of principle example in two dimensions. We expect these results to open a new route to the systematic exploration of quantum fragmentation.
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All authors Yiqiu Han, Oliver Hart, Alexey Khudorozhkov, Rahul Nandkishore

Strongly Correlated Electrons

Topochemically-engineered coexistence of charge and spin orders in intercalated endotaxial heterostructures

Samra Husremović, Wanlin Zhang, Medha Dandu et al. (+10 more)

Correlated electron systems that host multiple electronic orders offer routes to multifunctional quantum materials, but strong competition between these orders often prevents their coexistence. Here we show that nanoscale, metastable intercalated heterostructures can stabilize a rare combination of long-range magnetism and a commensurate charge density wave (C-CDW) order in a single material. We synthesize a two-dimensional (2D) metastable crystal, T/H-Fe$_x$TaS2, which comprises an endotaxial polytype heterostructure of 1T-TaS$_2$ and H-TaS$_2$ with Fe intercalated in the van der Waals interfaces. In T/H-Fe$_x$TaS2, Fe intercalants provide localized spins that support ferromagnetism, while 1T layers host a robust commensurate charge density wave (C-CDW) that persists to room temperature. In these intercalated heterostructures, Fe content simultaneously tunes ordering of spin and charge degrees of freedom, positioning topochemically-prepared intercalated endotaxial heterostructures as a route to stabilize and control competing quantum phases in 2D materials.
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All authors Samra Husremović, Wanlin Zhang, Medha Dandu, Berit H. Goodge, Isaac M. Craig, Ellis Kennedy, Matthew P. Erodici, Karen C. Bustillo, Chengyu Song, Jim Ciston, Sinéad Griffin, Archana Raja, D. Kwabena Bediako

Materials Science

Study of the Nonlinear Dependence of Anomalous Hall Conductivity on Magnetization in Weak Itinerant Ferromagnet ZrZn2

Surasree Sadhukhan, Stepan S. Tsirkin, Yaroslav Zhumagulov et al. (+1 more)

As opposed to the ordinary Hall effect, the anomalous Hall effect (AHE) remained unexplained for decades, and, amazingly, some misconceptions have survived even now, in particular, the claim that AHE is linearly related to the net magnetization. Karplus and Luttinger provided a quantum-mechanical explanation of AHE by explicitly including the SOC and the Berry curvature of electronic bands. They did address the question of linearity, but only in the relatively uncommon limit of the exchange coupling smaller than SOC. Now the linear relation in traditional ferromagnets is understood as a domain population effect: both AHE and magnetization are independently proportional to the domain disbalance. In this connection, it is interesting to check to what extent this relation will hold in single-domain itinerant ferromagnet, the closest case to that analyzed by Karplus and Luttinger? We answer this question by direct calculations, using the Karplus-Luttinger formula, of AHE in a prototypical itinerant ferromagnet, ZrZn$_2$. We show that in the zero-magnetization limit, $M\rightarrow 0$, the linear relation hold, but at rather small moments of $\sim 0.4\ \mu_B$/Zr breaks down completely and even flips the sign.
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All authors Surasree Sadhukhan, Stepan S. Tsirkin, Yaroslav Zhumagulov, Igor. I. Mazin

Soft Condensed Matter

Two-dimensional active polar semiflexible polymer under shear flow

A. Lamura and R. G. Winkler

The nonequilibrium structural and dynamical properties of semiflexible active polar polymers subject to linear flow are studied by numerical simulations. Filaments are confined in two dimensions and immersed in a fluid described by the Brownian Multiparticle Collision Dynamics approach. The applied shear flow causes conformational changes of a polymer, aligns it along the flow direction, and induces a tumbling motion at large flow rates. In an intermediate, activity-dependent shear-rate regime, a characteristic scaling exponent for the mean-square end-to-end distance along the gradient direction is observed. This exponent appears to be determined by the semiflexibility of the polymer. The tumbling dynamics exhibits a characteristic time, with a stronger dependence on the Weissenberg number than that of flexible active or passive polymers. Activity strongly impacts the rheological properties of the semiflexible polymers, and even implies a negative viscosity for weak flows. At very large values of the shear rate, shear dominates over activity and passive-polymer behavior is assumed.
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Disordered Systems and Neural Networks

Disorder averaging in random lattice models with periodic boundary conditions: Application to models with uncorrelated and correlated disorder

Balázs Hetényi, Luís Miguel Martelo and András Lászlóffy

Periodic boundary conditions are not always used in the study of disordered systems, but it can be advantageous to apply them to mimick thermodynamically large systems. In this case, polarization and its cumulants can not be obtained directly, but through the tools of the modern theory of polarization. This theory casts the polarization in crystalline systems as a geometric phase, rather than an operator expectation value. We develop disorder averaging techniques within the context of this theory which can calculate the variance of the polarization, its higher order moments, and the excess kurtosis (or Binder cumulant). We also derive an indicator of delocalization based on the degeneracy as a function of boundary conditions. We apply the computational techniques to two model systems. To test localization, we use a one-dimensional disordered model which is fully Anderson localized. Our calculations verify this. We also apply our techniques to the one dimensional de Moura-Lyra model, developed to study power law correlated (controlled by a parameter, $\alpha$) disorder. While this model is a pathological one, our method is validated. We also point out the significance of pairwise degeneracies found in the parameter range, $\alpha>2$ and near the band center (or near half filling), where the model was conjectured to exhibit a mobility edge.
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Materials Science · Cross-listed from physics.app-ph

High Breakdown Field Multi-kV UWBG AlGaN Transistors

Seungheon Shin, Kyle Liddy, Jon Pratt et al. (+6 more)

We demonstrate high-performance UWBG AlGaN PolFETs exhibiting a state-of-the-art combination of nearly 1 A/mm on-state current (~ 960 mA/mm) and large breakdown field (> 4.8 MV/cm) in high carrier density (1.15 x 1013 cm-2). Multi-kV robustness is successfully demonstrated exhibiting 1.28 and 2.17 kV by utilizing a gate-connected field plate structures in 3.9 and 6.8 {\mu}m LGD, corresponding to the extremely low specific on-resistance of 1.25 and 2.86 m{\Omega}cm2, respectively. High RF performance is also achieved, providing fT and fMAX, of 8.5 and 15 GHz, respectively, for 3.9 {\mu}m LGD. These results highlight UWBG AlGaN as a platform for both high-voltage RF and power applications.
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All authors Seungheon Shin, Kyle Liddy, Jon Pratt, Can Cao, Yinxuan Zhu, Brianna A. Klein, Andrew Armstrong, Andrew A. Allerman, Siddharth Rajan