Strongly Correlated Electrons
The Quantum Self-Consistent Harmonic Approximation: A Unified Framework for Quantum Spin System
G. C. Villela and A. R. Moura
The Self-Consistent Harmonic Approximation (SCHA) has been utilized to investigate
quantum and thermal phase transitions within
magnetic models and, more recently, in spintronic applications. The SCHA methodology involves utilizing simple harmonic
Hamiltonians, which are augmented with renormalization parameters that incorporate high-order fluctuations typically overlooked by conventional Linear
Spin-Wave (LSW) theories. Although this approach exhibits reasonable accuracy for models defined by large
spin values, its reliability diminishes when applied to
quantum systems with $S=1/2$. The traditional development of SCHA has incorporated semiclassical assumptions that obscure
quantum effects. In this study, we introduce a
quantum framework for the SCHA that eliminates the need for semiclassical approximations. Our
Quantum Self-Consistent Harmonic Approximation (QSCHA) utilizes the
spin coherent states formalism within a fully
quantum formulation. Consequently, we derive a novel renormalization parameter that accurately integrates
quantum corrections. To assess the efficacy of this new approach, we apply the QSCHA to analyze the critical temperature transitions across various well-documented
magnetic models. The findings, combined with the simplified operational procedure relative to other conventional interacting
spin-wave methodologies, suggest that QSCHA is a promising tool for advancing research in
quantum magnetism and spintronics.
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Mesoscale and Nanoscale Physics
Finite-frequency admittance and noise of a helical edge coupled to a magnet
Oliver Franke, Paula Koll, Peter G. Silvestrov et al. (+1 more)
The exchange coupling of the helical edge state of a
quantum spin-
Hall insulator with an easy-plane magnet has no effect on its DC electrical conductance if the magnet's anisotropy axis is aligned with the
spin quantization axis of the helical edge state [Meng et al., Phys. Rev. B 90, 205403 (2014)]. We here calculate the AC conductance $G_V(\omega)$ and the noise power $S_V(\omega)$ in the presence of a DC bias $V$. While both take the universal values $G_V({\omega = 0}) = e^2/h$ and $S_V(\omega = 0) = 4 e^2 k_{\rm B} T/h$ in the zero-frequency limit, $G_V(\omega)$ and $S_V(\omega)$ are quickly suppressed for finite $\omega$, so that low-frequency transport is effectively noiseless.
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All authors Oliver Franke, Paula Koll, Peter G. Silvestrov, Piet W. Brouwer
Superconductivity
Superconductivity of bilayer two-orbital Hubbard model for La$_{3}$Ni$_{2}$O$_{7}$ under high pressure
Wei-Yang Chen, Cui-Qun Chen, Meng Wang et al. (+2 more)
By combining density functional theory (DFT) and density
matrix renormalization group calculations, we investigate the unusual pressure dependence of superconducting transition temperature ($T_c$) in the nickelate
superconductor La$_{3}$Ni$_{2}$O$_{7}$. Using the hopping integrals and on-site potentials obtained by fitting the DFT band structures, we map a
quantum phase diagram of a
bilayer two-orbital Hubbard model with increasing pressure in a ladder geometry, which has an intermediate Hubbard repulsion and a Hund's coupling. Near $3/8$ filling, we find a strong
spin density wave order, which at $3/8$ filling shows a real-space
spin pattern similar to the
spin-charge stripe order along a
lattice direction. At $21/64$ filling, we find a superconducting phase with interlayer superconductivity (SC) in both the $d_{z^2}$ and $d_{x^2-y^2}$ orbitals, as well as in-plane SC in the $d_{z^2}$ orbital. Intriguingly, the SC is weakened with increasing pressure and transits to a Luttinger
liquid above $80$ GPa, which qualitatively agrees with the experimental observations of decreasing $T_c$ with increasing pressure and a transition to
Fermi liquid above $80$ GPa in La$_{3}$Ni$_{2}$O$_{7}$. Through a comparative study, we further show that the ratio of interaction to hopping integral, which reduces moderately with increasing pressure, may play a dominant role in the weakening of SC. Our results of this experimentally relevant model not only find a robust SC through suppressing the competing
spin density wave order, but also give new insight into the unusual pressure dependence of SC in La$_{3}$Ni$_{2}$O$_{7}$.
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All authors Wei-Yang Chen, Cui-Qun Chen, Meng Wang, Shou-Shu Gong, Dao-Xin Yao
Materials Science
Thermal tuning of dynamic response in Ag-based nanowire networks
J.I. Diaz Schneider, C. Gomez, C. Acha et al. (+3 more)
Self-assembled networks of metallic nanowires (NWs) are being intensively explored as test benches for neuromorphic proposals. In this work, we study the electric transport properties of dense self-assembled networks of Ag-based NWs (AgNWNs) coated with a thin insulating layer, using DC and AC stimuli. The building blocks of this network are the metallic NWs and the NW-NW junctions, either metallic or memristive. In the pristine state, frequency independence of the impedance reveals an over-percolated purely resistive network. A combination of low-temperature annealing and AC stimulus is shown to drastically affect the resistivity of the sample (interpreted as a depopulation of purely metallic junctions), unveiling a rich dynamic response. This procedure triggers the achievement of a capacitive response, which is successfully rationalized using a previously introduced 'two junction model'. Thermal treatment appears to be an indirect strategy to effectively modify the humidity content at the NW-NW intersections and, consequently, enable multiple switching schemes suitable for
brain-like processing alternatives.
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All authors J.I. Diaz Schneider, C. Gomez, C. Acha, P.E. Levy, E.D. Martínez, C.P. Quinteros
Materials Science · Cross-listed from cs.CE
A Synthesizability-Guided Pipeline for Materials Discovery
Thorben Prein, Willis O'Leary, Aikaterini Flessa Savvidou et al. (+2 more)
Computational materials discovery relies on the generation of plausible
crystal structures. The plausibility is typically judged through density functional theory methods which, while typically accurate at zero Kelvin, often favor low-energy structures that are not experimentally accessible. We develop a combined compositional and structural synthesizability score which provides an accurate way of predicting which compounds can actually be synthesized in a laboratory. We use it to evaluate non-synthesized structures from the Materials Project, GNoME, and Alexandria, and identified several hundred highly synthesizable candidates. We then predict synthesis pathways, conduct corresponding experiments, and characterize the products across 16 targets, successfully synthesizing 7 of 16. The entire experimental process was completed in only three days. Our results highlight omissions in lists of known synthesized structures, deliver insights into the practical utility of current materials databases, and showcase the central role synthesizability prediction can play in materials discovery.
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All authors Thorben Prein, Willis O'Leary, Aikaterini Flessa Savvidou, Elchaïma Bourneix, Joonatan E. M. Laulainen
Materials Science
Excitons in moiré superlattices with disordered electrons
Junghwan Kim, Dinh Van Tuan and Hanan Dery
Moiré superlattices in transition metal dichalcogenides (TMDs) heterobilayers exhibit various correlated insulating states driven by long-range Coulomb interactions, and these states crucially alter
exciton resonances, particularly at fractional fillings. We revisit a theoretical framework to investigate the doping dependence of
exciton spectra by extending hydrogenic
exciton wavefunctions, systematically analyzing how the 1$s$, 2$s$, and 3$s$ Rydberg states respond to moiré-induced mixing of $s$- and $p$-type orbitals. Notably, while the 1$s$ state remains relatively robust against doping, higher Rydberg
excitons show strong
redshifts and oscillator-strength quenching near specific fractional fillings. We incorporate both defect-induced quasi-ordering and thermal fluctuations to capture realistic device conditions, employing a large supercell approach. By selectively randomizing a subset of electrons or utilizing classical Monte Carlo simulations, we present direct calculations of
exciton spectra under varying defect densities and temperatures. Our results emphasize how even moderate disorder or finite temperature can partially or completely suppress characteristic moiré
exciton physics. Especially, we show how the 2$s$
exciton states respond to the phase transition in correlated electron states. This comprehensive picture not only clarifies recent experimental observations but also provides a framework to guide the design of moiré-based optoelectronic devices.
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Soft Condensed Matter
Capillary and priming pressures control the penetration of yield-stress fluids through non-wetting 2D meshes
Manon Bourgade, Nicolas Bain, Loïc Vanel et al. (+2 more)
Forcing hydrophilic fluids through hydrophobic porous solids is a recurrent industrial challenge. If the penetrating fluid is Newtonian, the imposed pressure has to overcome the capillary pressure at the fluid-air interface in a pore. The presence of a yield-stress, however, makes the pressure transfer and the penetration significantly more complex. In this study, we experimentally investigate the forced penetration of a water based yield-stress fluid through a regular hydrophobic mesh under quasi-static conditions, combining quantitative pressure measurements and direct visualisation of the penetration process. We reveal that the penetration is controlled by a competition between the yield-stress and two distinct pressures. The capillary pressure, that dictates the threshold at which the yield-stress fluid penetrates the hydrophobic mesh, and a priming pressure, that controls how the fluid advances through it. The latter corresponds to a pressure drop ensuing a local capillary instability, never reported before. Our findings shine a new light on forced imbibition processes, with direct implications on their fundamental understanding and practical engineering.
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All authors Manon Bourgade, Nicolas Bain, Loïc Vanel, Mathieu Leocmach, Catherine Barentin
Materials Science
Comparison between first-principles supercell calculations of polarons and the ab initio polaron equations
Zhenbang Dai, Donghwan Kim, Jon Lafuente-Bartolome et al. (+1 more)
Polarons are composite quasiparticles formed by excess charges and the accompanying
lattice distortions in solids, and play a critical role in transport, optical, and catalytic properties of
semiconductors and
insulators. The standard approach for calculating polarons from first principles relies on density functional theory and periodic supercells. An alternative approach consists of recasting the calculation of polaron wavefunction,
lattice distortion, and energy as a coupled nonlinear
eigenvalue problem, using the band structure,
phonon dispersions, and the electron-
phonon matrix elements as obtained from density functional perturbation theory. Here, we revisit the formal connection between these two approaches, with an emphasis on the handling of self-interaction correction, and we establish a compact formal link between them. We perform a quantitative comparison of these methods for the case of small polarons in the prototypical
insulators TiO2, MgO, and LiF. We find that the polaron wavefunctions and
lattice distortions obtained from these methods are nearly indistinguishable in all cases, and the formation energies are in good (TiO2) to fair (MgO) agreement. We show that the residual deviations can be ascribed to the neglect of higher-order electron-
phonon couplings in the density functional perturbation theory approach.
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All authors Zhenbang Dai, Donghwan Kim, Jon Lafuente-Bartolome, Feliciano Giustino
Materials Science
Charge disproportionation driven polar magnetic metallic double-layered perovskite Sr$_3$Co$_2$O$_7$
Hong-Fei Huang, Houssam Sabri, Jiadong Zang et al. (+1 more)
Strong coupling among spontaneous structural symmetric breaking, magnetism and
metallicity in an intrinsic polar
magnetic metal can give rise to novel physical phenomena and holds great promise for applications in spintronics. Here, we elucidate the mechanism of metallic ferroelectricity in the recently discovered polar metal Sr$_3$Co$_2$O$_7$. Our first-principles calculations reveal that both the spontaneous ferroelectric displacements and the
metallicity originate from charge disproportionation of Co ions. This is characterized by an inverted ligand-field splitting of the Co $t_2g$ orbitals at one site, while the metallic behavior is preserved by the t$_2g$ orbitals at both sites. The charge disproportionation stabilizes the asymmetric phase Within the framework of the on-site Hubbard U interaction. We thus propose that in related transition metal
oxides, charge disproportionation within specific orbitals can concurrently drive
metallicity and ferroelectricity, enabling strong coupling between these properties. More remarkably, this mechanism allows for the coexistence of magnetism, as evidenced in Sr$_3$Co$_2$O$_7$. Our findings highlight a promising avenue for realizing polar
magnetic metals and provide a new design principle for exploring multifunctional materials.
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All authors Hong-Fei Huang, Houssam Sabri, Jiadong Zang, Jie-Xiang Yu
Materials Science
Intrinsic Nonlinear Planar Thermal Hall Effect
Chanchal K. Barman
We introduce the intrinsic nonlinear planar thermal
Hall effect (NPTHE)– a dissipationless thermal response proportional to $(\nabla T)^2B$, which arises when the temperature gradient $\nabla T$ and
magnetic field $\mathbf{B}$ lie within the same plane. The effect originates from a thermal gradient induced correction to the Berry
curvature, characterized by the thermal Berry connection polarizability (TBCP) tensor, leading to a nonlinear transverse heat current independent of scattering time. A
symmetry analysis shows that the intrinsic NPTHE is permitted only in noncentrosymmetric
crystal point groups lacking horizontal mirror
symmetry. Using a tilted Dirac model, we demonstrate that its characteristic angular dependence provides an effective means to control the nonlinear thermal response. Our results establish a new class of
quantum geometry driven intrinsic nonlinear thermal transport, offering both a sensitive probe of band geometry and a pathway toward nonlinear thermal functionalities in
quantum materials.
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Strongly Correlated Electrons
Emergent charge-2$e$ carriers well hidden from electronic band structures
Muhammad Gaffar and Wei Ku
Emergence of charge-2$e$ bosonic carriers as tightly bound electrons offer perhaps the simplest route to understand the non-
Fermi liquid behaviors widely observed in functional materials. However, such scenarios are often discarded when electronic carriers are observed with well-defined energy-momentum dispersion. Here, using attractive Hubbard model as a representative example, we demonstrate the emergence of such 2$e$-carriers coexisting with residual electronic carriers through determinant
quantum Monte Carlo computation of their propagators. Interesting, even already dominant in density, the emergent 2$e$-carriers appear to efficiently elude detection by the electronic spectral function, which still shows good quasi-particles with negligible mass enhancement. Nonetheless, above the superfluid temperature, the presence of 2$e$-carriers is revealed through a pseudogap in the electronic spectral function. Our results exemplify the risk of common practice in discarding strong correlation in materials solely based on observation of clean band structures with weakly enhanced mass. More importantly, our finding provides the microscopic foundation for scenarios of
boson-
fermion mixed
liquid as effective descriptions for some of the correlated functional materials.
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Strongly Correlated Electrons
Critical theory of Pomeranchuk transitions via high-dimensional bosonization
Zhengfei Hu, Jaychandran Padayasi, Oğuz Türker et al. (+1 more)
We use high-dimensional bosonization to derive an effective field theory that describes the Pomeranchuck transition in isotropic two-dimensional
Fermi liquids. We find that the transition is triggered by the softening of an eigenmode that leads to spontaneous
Fermi surface distortion. The resultant theory in terms of this critical mode has dynamical critical exponent $z = 2$ and the upper critical dimension is $d_c = 4-z= 2$. As a result the system is at the upper critical dimension in 2D, resulting in a Gaussian fixed point with a marginally irrelevant quartic perturbation.
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All authors Zhengfei Hu, Jaychandran Padayasi, Oğuz Türker, Kun Yang
Mesoscale and Nanoscale Physics
Spontaneous Raman Scattering under Vibrational Strong Coupling: The Critical Role of Polariton Spatial Mode Coherence
Maxime Dherbécourt, Joël Bellessa, Clémentine Symonds et al. (+2 more)
Resonant coupling of a vibration to a cavity mode has been reported to dramatically modify spontaneous Raman scattering, but subsequent studies have produced conflicting results. In this Letter, we develop a microscopic
quantum framework that captures the spatial structure of polaritonic modes. In a homogeneously filled cavity, spatial overlap between polaritons and cavity resonances enforces selection rules that suppress the initially reported polaritonic Raman peaks, consistent with most experiments. In contrast, for a quasi-two-dimensional (2D) molecular layer, these rules are lifted, yielding Raman peaks at the polariton energies. Our Letter clarifies that the Raman response under vibrational strong coupling is determined by cavity-vibration spatial mode overlap and offers a framework for Raman studies of strongly coupled quasi-2D systems.
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All authors Maxime Dherbécourt, Joël Bellessa, Clémentine Symonds, Guillaume Weick, David Hagenmüller
Mesoscale and Nanoscale Physics · Cross-listed from quant-ph
Initial-State Typicality in Quantum Relaxation
Ruicheng Bao
Relaxation in open
quantum systems is fundamental to
quantum science and technologies. Yet, the influence of the initial state on relaxation remains a central, largely unanswered question. Here, by systematically characterizing the relaxation behavior of generic initial states, we uncover a typicality phenomenon in high-dimensional open
quantum systems: relaxation becomes nearly initial-state-independent as system size increases under verifiable conditions. Crucially, we prove this typicality for thermalization processes above a size-independent temperature. Our findings extend the typicality to open
quantum dynamics, in turn identifying a class of systems where two widely used quantities – the Liouvillian gap and the maximal relaxation time – merit re-examination. We formalize this with two new concepts: the 'typical strong Mpemba effect' and the 'typical relaxation time'. Beyond these conceptual advances, our results provide practical implications: a scalable route to accelerating relaxation and a typical mixing-time
benchmark that complements conventional worst-case metrics for
quantum simulations and state preparation.
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Mesoscale and Nanoscale Physics
Phason-driven temperature-dependent transport in moiré graphene
Alex Boschi, Alejandro Ramos-Alonso, Vaidotas Mišeikis et al. (+9 more)
The electronic and vibrational properties of 2D materials are dramatically altered by the formation of a moiré superlattice. The lowest-energy
phonon modes of the superlattice are two acoustic branches (called phasons) that describe the sliding motion of one layer with respect to the other. Considering their low-energy dispersion and damping, these modes may act as a significant source of scattering for electrons in moiré materials. Here, we investigate temperature-dependent electrical transport in minimally twisted
bilayer graphene, a moiré system developing multiple weakly-dispersive electronic bands and a reconstructed
lattice structure. We measure a linear-in-temperature resistivity across the band manyfold above $T\sim{10}$ K, preceded by a quadratic temperature dependence. While the linear-in-temperature resistivity is up to two orders of magnitude larger than in monolayer
graphene, it is reduced (approximately by a factor of three) with respect to magic-angle twisted
bilayer graphene. Moreover, it is modulated by the recursive band filling, with minima located close to the full filling of each band. Comparing our results with a semiclassical transport calculation, we show that the experimental trends are compatible with scattering processes mediated by longitudinal phasons, which dominate the resistivity over the contribution from conventional acoustic
phonons of the monolayer. Our findings highlight the close relation between vibrational modes unique to moiré materials and carrier transport therein.
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All authors Alex Boschi, Alejandro Ramos-Alonso, Vaidotas Mišeikis, Kenji Watanabe, Takashi Taniguchi, Fabio Beltram, Stiven Forti, Antonio Rossi, Camilla Coletti, Rafael M. Fernandes, Héctor Ochoa, Sergio Pezzini
Mesoscale and Nanoscale Physics
Unconventional relativistic spin polarization of electronic bands in an altermagnet
A. Dal Din, D.A. Usanov, L. Šmejkal et al. (+22 more)
Altermagnetism is a recently identified phase with a d, g or i-wave
spin symmetry of
magnetic ordering. Its discovery opens new research fronts at intersections of magnetism and spintronics with fields ranging from superconductivity to topological and relativistic
quantum physics. Here we demonstrate an unconventional relativistic
spin polarization in an altermagnet by
spin and angle resolved photoemission spectroscopy of electronic bands in single-domain MnTe. The relativistic
spin-orbit coupling origin is revealed by observing that the alternating momentum-dependent
spin polarization is orthogonal to the
magnetic-ordering vector. The collinearity, even-parity and time-reversal-odd nature of the demonstrated relativistic
spin polarization in the altermagnet is unparalleled in conventional forms of the relativistic
spin polarization. Our experimental results and methodology are supported by non-relativistic
spin-
symmetry and relativistic
magnetic-
symmetry analyses, and microscopic ab initio ground-state and photoemission theory.
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All authors A. Dal Din, D.A. Usanov, L. Šmejkal, S. W. D'Souza, F. Guo, O. J. Amin, E. M. Dawa, R. P. Campion, K. W. Edmonds, B. Kiraly, A. W. Rushforth, C. Polley, M. Leandersson, E. Golias, Y. Niu, S. Telkamp, F. Krizek, A. Birk Hellenes, J. Priessnitz, W. H. Campos, J. Krempaský, J. Minár, T. Jungwirth, J. H. Dil, P. Wadley
Soft Condensed Matter · Cross-listed from physics.bio-ph
Information bounds the robustness of self-organized systems
Nicolas Romeo, David G. Martin, Mattia Scandolo et al. (+3 more)
Self-organized systems, from synthetic nanostructures to developing organisms, are composed of fluctuating units capable of forming robust functional structures despite noise. Here, we ask: are there fundamental bounds on the robustness of noisy self-organized systems? By viewing self-organization as noisy encoding, we prove that the positional information capacity of short-range classical systems with discrete states obeys a bound reminiscent of area laws for
quantum information. We illustrate this principle with
lattice models whose dynamics is captured by continuum models derived using exact coarse-graining techniques and validated through Dynamical Renormalization Group calculations. The universal bound is saturated by fine-tuning transport coefficients, which can be rationalized in the continuum limit upon considering the effects of boundaries on domain wall dynamics. We illustrate how this limit can be bypassed when long-range correlations are present by investigating a wave-pinning model motivated by biological mechanisms. In this class of models, global constraints reduce the need for fine-tuning by providing effective integral feedback. Our work identifies fundamental limits for the ability of natural and synthetic microsystems to self-assemble into patterns and rationalizes them on purely information-theoretic grounds.
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All authors Nicolas Romeo, David G. Martin, Mattia Scandolo, Michel Fruchart, Edwin M. Munro, Vincenzo Vitelli
Mesoscale and Nanoscale Physics
Observation of Long-Lifetime Magnon Pairs by Fano Resonance of Photons
Qian-Nan Huang, Zhiping Xue and Tao Yu
Mode fluctuations with a long lifetime are essential for
quantum information and logic operations in magnonic devices. We probe the broadband nonlinear magnetization dynamics of a high-quality ferromagnet under a strong microwave drive using microwave spectroscopy. We observe an unexpected Fano resonance in the microwave transmission when the driven amplitude of the magnetization is large and the drive frequency $\omega_d$ is close to but not at the
ferromagnetic resonance. We interpret this Fano resonance by a scattering theory of
photons considering the three-
magnon interaction between the Kittel
magnon and
magnon pairs with opposite wave vectors of frequency $\omega_d/2$. The theoretical model suggests that the microwave spectroscopy measures the dynamics of the fluctuation $\delta \hat{\alpha}$ of the Kittel
magnon and $\delta\hat{\beta}_{\pm k}$ of the
magnon pairs over the driven steady states, which are coupled coherently by the steady-state amplitudes. With the damping of $\delta\hat{\beta}_{\pm k}$ much smaller than that of $\delta \hat{\alpha}$, the theoretical calculation well reproduces the observed Fano resonance, indicating the
magnon pairs hold a recorded long lifetime.
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Strongly Correlated Electrons
Quantum critical behavior of diluted quasi-one-dimensional Ising chains
Logan Sowadski and Thomas Vojta
CoNb$_2$O$_6$ is a unique
magnetic material. It features bulk three-dimensional
magnetic order at low temperatures, but its
quantum critical behavior in a
magnetic field is well described by the one-dimensional transverse-field Ising universality class. This behavior is facilitated by the structural arrangement of
magnetic Co$^{2+}$ ions in nearly isolated zig-zag chains. In this work, we investigate the effect of random site dilution on the critical properties of such a quasi-one-dimensional
quantum Ising system. To this end, we introduce an anisotropic site-diluted three-dimensional transverse-field Ising model. We find that site dilution leads to unconventional activated scaling behavior at the
quantum phase transition. Interestingly, the critical exponents of the
quantum critical point are in good agreement with those of the disordered three-dimensional transverse-field Ising universality class, despite the strong spatial anisotropy. We discuss the generality our findings as well as implications for experiments.
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Strongly Correlated Electrons
Is ruthenium dioxide altermagnet?
Alexander A. Tsirlin, Ece Uykur and Oleg Janson
Ruthenium dioxide was named as one of the first and most promising altermagnetic candidates with $d$-wave
symmetry. We summarize key findings for this material and critically discuss prospects of making it altermagnetic.
Statistical Mechanics
Exact Combinatorial Density of States for the Critical 1D Ising Model
Bastian Castorene, Francisco J. Peña, Martin HvE Groves et al. (+1 more)
This work presents an exact microcanonical combinatorial analysis of the one-dimensional
antiferromagnetic Ising model. At the primary ground-state level crossing $B/J=2$, degeneracies follow the Fibonacci and Lucas sequences for open chains and periodic rings, respectively. We extend this framework to the complete excitation spectrum, demonstrating that the density of states is constructed from topological defects governed by linear Diophantine equations and $p$-fold Fibonacci convolutions. Open boundaries act as fractional defects, densifying the chain spectrum into energy steps of $2J$, whereas the closed ring remains quantized in units of $4J$. Notably, this exact topological counting exposes non-trivial spectral gaps near the fully polarized limit, strictly forbidding the penultimate macroscopic energy levels in both
topologies. Through the transfer
matrix formalism, we derive exact closed-form expressions for the critical degeneracies at all energy levels. These results provide a rigorous analytical foundation for extracting exact residual
entropies and exposing the intrinsic number-theoretic architecture of
quantum critical
manifolds.
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All authors Bastian Castorene, Francisco J. Peña, Martin HvE Groves, Patricio Vargas
Soft Condensed Matter · Cross-listed from physics.med-ph
A Multiscale Framework for In Silico Thrombus Generation and Photoacoustic Simulations
Hamed Ghodsi, Sara Cardona, Behrooz Fereidoonnezhad et al. (+1 more)
Thrombus microstructure plays a critical role in determining the treatment success for thrombus-related diseases such as stroke and deep vein thrombosis. However, no in vivo diagnostic method can fully capture thrombus microstructure yet. Photoacoustic imaging is uniquely positioned to provide information on thrombi composition as it relays optical absorption information from diffuse
photons at acoustic propagation depths. Computational modeling enables systematic exploration of microstructural effects on imaging signals, offering insights into developing improved in vivo diagnostic techniques. However, no photoacoustic simulation platform can model microstructural features within centimeter-scale phantoms at reasonable computational cost. Here, we present REFINE, a
topology-driven framework for generating in silico thrombi replicating its key replicating their key microstructural traits. REFINE enables controlled, recursive optimization of thrombus
topology, making it suitable for accurate photoacoustic modeling and potentially powerful for biomechanical analyses. These digital thrombi are embedded into a multiscale photoacoustic simulation platform that bridges microscale acoustic modeling with macroscale thrombus geometries, enabling efficient and realistic simulation of photoacoustic signal responses. We created unique thrombi microstructure for various compositions and porosities. Our simulation framework effectively links microstructural features to macroscale imaging outcomes, in agreement with previous empirical studies. Our results demonstrate that thrombus microstructure significantly affects photoacoustic spectral responses and can be modeled in silico. These findings highlight that multiscale photoacoustic simulation is a powerful tool for characterizing tissue microstructure and that our framework enables in silico thrombi analysis and diagnostic imaging strategy development
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All authors Hamed Ghodsi, Sara Cardona, Behrooz Fereidoonnezhad, Sophinese Iskander-Rizk
Mesoscale and Nanoscale Physics
Nonlinear transport fingerprints of tunable Fermi-arc connectivity in magnetic Weyl semimetal Co$_3$Sn$_2$S$_2$
K. X. Jia, H. C. Li, M. H. Zou et al. (+2 more)
Fermi arcs in Weyl semimetals provide a unique platform for surface-state engineering, yet di rectly tracking of their
evolution under surface tuning remains experimentally challenging. Here we theoretically propose that nonreciprocal charge transport can serve as a direct probe of
Fermi arc Lifshitz transitions (FALT). We show that different surface terminations in Co3Sn2S2 can produce f inite and highly tunable second-order nonreciprocal signals, which can be further modulated by adjusting the surface potential. Strikingly, we show that the second-order conductivity exhibits sign changes as the
Fermi arc connectivity is tuned across FALT driven by gating or chemical potential variation. This behavior arises from the
chiral nature of electron velocities on the
Fermi arcs, and is highly sensitive to surface termination and
symmetry breaking. Our findings establish nonreciprocal transport as an electrically measurable fingerprint of FALT and propose new strategies that could be directly applied in devices for in situ engineering and detecting transport properties in topological materials.
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All authors K. X. Jia, H. C. Li, M. H. Zou, H. Geng, Hua Jiang
Statistical Mechanics · Cross-listed from hep-th
2D or not 2D: a "holographic dictionary" for Lowest Landau Levels
Gautam Mandal, Ajay Mohan and Rushikesh Suroshe
We consider 2D
fermions on a plane with a perpendicular
magnetic field, described by Landau levels. It is wellknown that, semiclassically, restriction to the lowest Landau levels (LLL) implies two constraints on a 4D phase space, that transforms the 2D coordinate space (x,y) into a 2D phase space, thanks to the non-zero Dirac bracket between x and y. A naive application of Dirac's prescription of quantizing LLL in terms of L2 functions of x (or of y) fails because the wavefunctions are functions of x and y. We are able, however, to construct a 1D QM, sitting differently inside the 2D QM, which describes the LLL physics. The construction includes an exact 1D-2D correspondence between the
fermion density \rho(x,y) and the Wigner distribution of the 1D QM. In a suitable large N limit, (a) the Wigner distribution is upper bounded by 1, since a phase space
cell can have at most one
fermion (Pauli exclusion principle) and (b) the 1D-2D correspondence becomes an identity transformation. (a) and (b) imply an upper bound for the
fermion density \rho(x,y). We also explore the
entanglement entropy (EE) of subregions of the 2D noncommutative space. It behaves differently from conventional 2D systems as well as conventional 1D systems, falling somewhere between the two. The main new feature of the EE, directly attributable to the noncommutative space, is the absence of a logarithmic dependence on the size of the entangling region, even though there is a
Fermi surface. In this paper, instead of working directly with the Landau problem, we consider a more general problem, of 2D
fermions in a rotating harmonic trap, which reduces to the Landau problem in a special limit. Among other consequences of the emergent 1D physics, we find that post-quench dynamics of the (generalized) LLL system is computed more simply in 1D terms, which is described by well-developed methods of 2D phase space hydrodynamics.
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Mesoscale and Nanoscale Physics · Cross-listed from physics.app-ph
Md. Anamul Hoque, Zoltán Kovács-Krausz, Bing Zhao et al. (+5 more)
Graphene is a promising platform for
spin-based non-volatile
memory, logic, and neuromorphic computing by combining long-distance
spin transport with electrical tunability at room temperature. However, advancing beyond passive
spin channels requires devices capable of generating large
spin signals with efficient rectification capabilities, which are essential for active spintronic components. Here, we demonstrate a folded-
bilayer graphene spin-valve device with
giant non-local
spin signals in the several mV range with pronounced
spin-rectification effects. Efficient
spin injection creates a significant
spin accumulation of 20 meV and generates a
spin diode effect with an asymmetry of over an order of magnitude between forward and reverse bias conditions. This
spin-diode effect is expected to arise from nonlinear
spin-charge interactions in the folded-
bilayer graphene channel. These observed large
spin signals and
spin-diode effects in
graphene systems offer a promising platform for developing active two-dimensional spintronic devices.
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All authors Md. Anamul Hoque, Zoltán Kovács-Krausz, Bing Zhao, Prasanna Rout, Ivan Vera Marun, Szabolcs Csonka, Péter Makk, Saroj P. Dash
Mesoscale and Nanoscale Physics
Coherent control of Floquet-engineered magnon frequency combs
Christopher Heins, Amelie L. Fehrmann, Lukas Körber et al. (+5 more)
Frequency combs represent a hallmark of coherence emerging from nonlinear dynamics, where periodic driving organizes energy into a precisely spaced spectral structure. Extending this concept to collective excitations in solids such as
magnons, the quanta of
spin waves in magnetically ordered materials, offers a powerful route to control energy flow, coherence, and information processing in condensed matter systems. Here, we demonstrate deterministic control of Floquet-engineered
magnon frequency combs in
magnetic vortices using nanosecond voltage pulses. By tuning the pulse duration and timing, we control the nonlinear energy transfer between
magnons and the
vortex core, enabling the Floquet-engineered initiation or suppression of
magnon frequency combs far below their spontaneous instability threshold. This pulse-programmable interaction allows the
vortex to sustain
magnon-driven auto-oscillation with high phase stability, or to revert to its static ground state on demand. Our results establish
vortex-based
magnetic systems as a robust solid-state platform for Floquet engineering, bridging nonlinear
spin dynamics with frequency conversion and coherent
spin-based
quantum devices.
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All authors Christopher Heins, Amelie L. Fehrmann, Lukas Körber, Joo-Von Kim, Attila Kákay, Jürgen Fassbender, Katrin Schultheiss, Helmut Schultheiss
Strongly Correlated Electrons
From Wavefunction Sign Structure to Static Correlation
Matúš Dubecký
A variational nodal partition of the correlation energy is introduced, $E_{\mathrm{cor}}=E_{\mathrm{sym}}+E_{\mathrm{stat}}$, relative to a chosen mean-field correlation baseline and its associated single-determinant node. Static correlation $E_{\mathrm{stat}}$ is the negative of the energy penalty incurred when the many-electron wavefunction is constrained to that reference node rather than the exact one. This nodal term isolates the antisymmetric, sign-structure component of correlation, while the complementary symmetric term $E_{\mathrm{sym}}$ necessarily contains dynamic correlation together with a distinct strong but nodeless contribution. The resulting state-based, method-independent framework clarifies the relation between dynamic, nondynamic, strong, and static correlation, places earlier node-based decompositions on rigorous footing, and explains why single-determinant fixed-node
diffusion Monte Carlo can be highly accurate in some systems yet fail in others.
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Superconductivity
Transverse superconducting diode without parity and time-reversal violation
Ruo-Peng Yu, Jin-Xin Hu and Zi-Ting Sun
The superconducting diode effect (SDE) is characterized by its nonreciprocal nature in critical supercurrents. However, realizing a longitudinal SDE typically requires simultaneous time-reversal ($\mathcal{T}$) and inversion ($\mathcal{P}$)
symmetry breaking in the device, raising challenges in applications. In this Letter, we reveal that an off-axis direct-current bias applied to a planar anisotropic
superconductor can convert intrinsic anisotropy into transverse nonreciprocity, generating ultra-tunable SDE without breaking either $\mathcal{P}$ or $\mathcal{T}$
symmetry. Using both Ginzburg-Landau theory and self-consistent mean-field calculations, we show that diode efficiency can be continuously tuned via bias current amplitude. Notably, when the injected bias current exceeds a critical threshold, the system is driven into a “unidirectional superconductivity" regime, where transverse dissipationless currents are permitted in only one direction. Based on this mechanism, we propose the “current-gated orthogonal superconducting transistor (CGOST)" and demonstrate its utility in tunable supercurrent range controllers and half-wave rectifiers. Our findings open new avenues for nonreciprocal superconducting electronics.
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Mesoscale and Nanoscale Physics
High-temperature superconducting Majorana fermions platforms in the layered Kitaev Materials: Case study of $Li_2IrO_3$
Elnaz Rostampour and Badie Ghavami
Recent advances in Kitaev materials have highlighted their potential to host Majorana
fermions without or high-temperature of superconductivity. In this research, we propose $Li_2IrO_3$ as a promising High-temperature superconducting platform supporting Majorana edge modes due to its strong
spin-orbit coupling, honeycomb
lattice structure, and proximity to a
quantum spin liquid (QSL) phase. A theoretical and numerical framework based on the Kitaev-Heisenberg
Hamiltonian is developed to model
spin interactions in $Li_2IrO_3$. Here, the existence of topological zero-energy states is demonstrated, and their signatures in the edge-localized spectral weight are identified. A device concept based on this material is also proposed with potential industrial applications in spintronics,
magnetic field sensing, and topological
quantum memory.
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Materials Science
Predictive quantum vibrational spectra through active learning 4G-NNPs
Md Omar Faruque, Dil K. Limbu, Nathan London et al. (+1 more)
Predictive simulation of vibrational spectra of complex condensed-phase and interface systems with thousands of degrees of freedom has long been a challenging task of modern condensed matter theory. In this work, fourth-generation high-dimensional committee neural network potentials (4G-HDCNNPs) are developed using active learning and query-by-committee, and introduced to the essential
nuclear quantum effects (NQEs) as well as conformational
entropy and anharmonicities from path integral (PI) molecular dynamics simulations. Using representative bulk water and air-water interface test cases, we demonstrate the accuracy of the developed framework in infrared spectral simulations. Specifically, by seamlessly integrating non-local charge transfer effects from 4G-HDCNNPs with the NQEs from PI methods, our introduced methodology yields accurate infrared spectra using predicted charges from the 4G-HDCNNP architecture without explicit training of dipole moments. The framework introduced in this work is simple and general, offering a practical paradigm for predictive spectral simulations of complex condensed phases and interfaces, free from empirical parameterizations and ad hoc fitting.
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All authors Md Omar Faruque, Dil K. Limbu, Nathan London, Mohammad R. Momeni