Papers

Toward measuring the thermal properties of exfoliated atomically thin materials, we demonstrate simultaneous measurements of the thermal conductivity and specific heat in suspended membranes. We use the 3{\omega} technique applied to quasi-two-dimensional silicon nitride membranes having a metal line heater patterned on the surface to both deliver heat and directly measure the thermal impedance of the membrane at the heating frequency, Z(2{\omega}). We derive an expression for the complex thermal impedance as a function of frequency, approximating the actual rectangular membranes with a one dimensional model. The derivation accounts for potential parasitic heat loss mechanisms including conduction along the heater line, and by the gas load in an imperfect vacuum. Qualitatively, the thermal impedance response resembles a low-pass filter, owing to the combination of the total thermal resistance and total specific heat. Fitting Z(2{\omega}) to measurements across a few decades in frequency, we extract values of the thermal conductivity and specific heat of silicon nitride in agreement with literature values. We also study the dependence on the heating current, and compare to measurements of the thermal conductivity at zero frequency.

Materials with broken fundamental symmetries, such as chiral crystals, provide a rich playground for exploring unconventional spin-dependent transport phenomena. The interplay between a material's chirality, strong spin-orbit coupling, and charge currents can lead to complex non-reciprocal effects, where electrical resistance depends on the direction of current and magnetic fields. In this study, we systematically investigate the angular dependencies of magnetoresistance in single-crystalline chiral Tellurium (Te). We observe distinct non-reciprocal magnetoresistances for magnetic fields applied along three orthogonal directions: parallel to the current along the chiral axis (z), in the sample plane but perpendicular to the current (y), and out of the sample plane (x). Through detailed analysis of the chirality- and thickness-dependence of the signals, we successfully disentangle multiple coexisting mechanisms. We conclude that the Edelstein effect, arising from the chiral structure's radial spin texture, is responsible for the non-reciprocity along the z-axis. In contrast, the chirality-independent signal along the y-axis is attributed to the Nernst effect, and the non-reciprocity along the x-axis may originate from intrinsic orbital magnetizations. These findings elucidate the complex interplay of spin, orbital, and thermal effects in Te, providing a complete picture of its non-reciprocal transport properties.

Pair density waves (PDW) are novel forms of superconducting states that exhibit periodically modulated pairing. A remaining challenge is to elucidate how intrinsic PDW order can emerge robustly in strongly correlated electrons. Here we propose that PDW is prone to form in strongly coupled multiband superconductors simply with interband Cooper pairing between electrons from oppositely dispersing bands. This scenario is heuristically motivated by the observation that uniform interband pairing in such systems would exhibit negative superfluid weight – a signature of an instability towards pairing modulation, implying that PDW emerges naturally in the true ground state. Using large-scale density-matrix-renormalization-group calculations with finite-size scaling analysis, we demonstrate this PDW mechanism in a minimal model with strong interband attractions. Our simulations reveal power-law superconducting correlations characterized by incommensurate modulations. The exponent $K_{sc}$ of the power-law PDW correlation decreases systematically with increasing ladder width, confirming a genuine long-range PDW order in the 2D limit. Our study therefore demonstrates a promising route to robust PDW states in multiband systems.

Engineering electron correlations in quantum dot arrays demands navigation of high-dimensional, non-convex parameter spaces where hole doping fundamentally alters the physics. We present a comparative study of two control paradigms for the one-hole, half-filled Hubbard model: (i) systematic physics-guided design and (ii) autonomous deep reinforcement learning with geometry-aware neural architectures. While systematic analysis reveals key design principles, such as field-induced localization for trapping the mobile hole, it becomes computationally intractable for optimization. We show that an autonomous RL agent, benchmarked across five 3D lattices from tetrahedron to FCC, achieves human-competitive accuracy (R^2 > 0.97) and 95.5 percent success on held-out tasks. The agent is 3-4 orders of magnitude more sample-efficient than grid search and outperforms other black-box optimization methods. Transfer learning yields 91 percent few-shot generalization to unseen geometries. This work establishes autonomous RL as a viable and highly efficient framework for rapid optimization and non-obvious strategy discovery in complex quantum systems.

We study Anderson localization of a one-dimensional quantum droplet in a speckle-like potential employing the generalized Gross-Pitaevskii equation. We compute the droplet width, density profiles, diffusion exponent and coefficient, and the localization length for both small and large droplets. Interesting classes of anomalous diffusions are obtained in transport dynamics ranging from superdiffusion to subdiffusion for a strong disorder strength. We find that above a certain critical disorder strength the droplet exhibits a transition to Anderson localization. Our results can be redibly probed with recent experiments.

The evolution of a system coupled to baths is commonly described by a master equation that, in the long-time limit, yields a steady-state density matrix. However, when the same evolution is unraveled into quantum trajectories, it is possible to observe a transition in the scaling of entanglement within the system as the system-bath coupling increases - a phenomenon that is invisible in the trajectory-averaged reduced density matrix of the system. Here, we go beyond the paradigm of trajectories from master equations and explore whether a qualitatively analogous entanglement-scaling transition emerges in a single unitary evolution of the combined system-bath setup, without monitoring the dynamics of the system. We investigate the scaling of entanglement in a unitary quantum setup composed of a two-dimensional lattice of free fermions, where each site is coupled to a fermionic bath. As the system-bath coupling increases, the logarithmic fermionic negativity reveals an entanglement transition from logarithmic-law to area-law scaling. This occurs while the system's steady-state properties are trivial, highlighting that the signatures of these different scalings are within the bath-bath correlations. Evidence of the transition is also found in the mutual information and the correlations of the full system-bath setup, suggesting that the entanglement transition is underpinned by a change in the spatial structure of quantum information.

Quantum geometric electronic responses are often viewed through a non-interacting lens: independent quasiparticles accumulate Berry phases as they move through a static crystal and background potential. Here we argue that the combined action of electron-electron interactions and an out-of-equilibrium many-body state can produce striking departures from this familiar picture. We demonstrate how nonequilibrium exchange interactions produce a nonequilibrium collective quantum geometry distinct from that of its equilibrium ground state. We find this manifests as an exchange induced nonlinear Hall effect with nonlinear Hall current signals competitive with that of well-known non-interacting mechanisms. This highlights the critical role electron interactions and nonequilibrium states can play in the nonlinear response of quantum matter.

We investigate the interplay of particle-hole symmetry and sub-Brillouin zone (sBZ) topology by coupling a so-called Chern dartboard insulator (CDI) to a superconductor (SC) via the proximity effect. We dub the hybrid system, and equivalent intrinsically superconducting phases, a Chern dartboard superconductor (CDSC). We show that a CDSC can have nontrivial sBZ topology if it arises from a CDI that has an even number of mirror symmetries $n$. On the other hand, particle-hole symmetry constrains a CDSC that arises from an odd-$n$ CDI to have trivial sBZ topology. However, we can circumvent this constraint for $n=1$ by inducing an FFLO-type pairing or shifting the CDI in momentum space, converting the mirror symmetry to a momentum-space nonsymmorphic mirror symmetry. With a superconducting pairing that preserves the (nonsymmorphic) mirror symmetries, even-$n$ CDIs and the shifted $n=1$ CDI can realize the minimal spinless phase that has a trivial total Chern number and nontrivial reduced Chern numbers. With a pairing that breaks the mirror symmetries, the hybrid system can realize phases that have nontrivial total and reduced Chern numbers, expanding the classification of phases that have sub-Brillouin zone (sBZ) topology. We also predict that some types of $n=2$ CDSCs inherit the quantized crystalline response of the $n=2$ CDI, providing experimentalists with a well-defined way to probe the CDSC. Our work motivates further exploration of sBZ topology, bulk topology, and quantized response.

We report the results and unique instrument configuration of a novel experiment in which we successfully transitioned a DPPH sample from its natural paramagnetic state and essentially a non-magnetic material to a ferromagnetic state at room temperature. This was achieved using a specifically applied helical flux magnetic field. The DPPH sample (2,2-diphenyl-1-picrylhydrazyl) remained ferromagnetic for at least one hour after the experiment, indicating that a transformation in the material was induced by the external field rather than being merely a temporary magnetic phase transition observed only during the experiment. The external magnetic field used had a helical pitch angle of approximately $54.7{\deg}$, known mathematically as the Magic Angle, relative to the +z-axis, which is aligned with the normal S to N external field's magnetic moment vector. Based on the phenomenology of the experiment and results, we suggest that this specific magic angle corresponding to the known quantization precession spin angle of free electrons under a homogeneous straight flux magnetic field potentially enhances the percentage of unpaired valence electrons within the DPPH material, allowing them to align in parallel with the applied external field. Typically, in paramagnetic materials, the distribution of unpaired electrons' quantum spins relative to an external field is nearly random, showing roughly a 50% chance of either parallel or antiparallel alignment. Only a slight majority preference exists in one alignment direction due to the Boltzmann thermal distribution, which contributes to the paramagnetic nature of these materials. In our measurements, we found that the induced ferromagnetism of the DPPH sample resulted in an abnormal thousand-fold decimal value increase in relative magnetic permeability at ${\mu}{\approx}1.4$, compared to its typical paramagnetic value of $1.0001$ for this material.

The discovery of high-T$_c$ superconductivity in La$_3$Ni$_2$O$_7$ has opened the door to a new route to high temperature superconductivity, distinct from that in cuprates and iron-based materials. Yet, despite intense recent activity, we lack experimentally testable protocols for distinguishing between different pairing scenarios. In this Letter, we construct a minimal two-band model that reproduces the Fermi-surface topology observed in recent ARPES measurements and DFT calculations, and we analyze superconductivity arising from two distinct pairing mechanisms. We show that these mechanisms yield sharply different responses to an applied perpendicular electric field. Thus, La$_3$Ni$_2$O$_7$ offers the unique opportunity to cleanly distinguish between different pairing scenarios. Finally, we propose three concrete experimental proposals designed to distinguish these scenarios and thereby identify the pairing mechanism most relevant to the real material.

As a core technology for green chemical synthesis and electrochemical energy storage, electrocatalysis is central to decarbonization strategies aimed at combating climate change. In this context, computational and machine learning driven catalyst discovery has emerged as a major research focus. These approaches frequently use the thermodynamic overpotential, calculated from adsorption free energies of reaction intermediates, as a key parameter in their analysis. In this paper, we explore the large-scale applicability of such overpotential estimates for identifying good catalyst candidates by using datasets from the Open Catalyst Project (OC20 and OC22). We start by quantifying the uncertainty in predicting adsorption energies using ab initio methods and find that $\sim$0.3-0.5 eV is a conservative estimate for a single adsorption energy prediction. We then compute the overpotential of all materials in the OC20 and OC22 datasets for the hydrogen and oxygen evolution reactions. We find that while the overpotential allows the identification of known good catalysts such as platinum and iridium oxides, the uncertainty is large enough to misclassify a broad fraction of the datasets as “good”, which limits its value as a screening criterion. These results question the reliance on overpotential estimation as a primary evaluation metric to sort through catalyst candidates and calls for a shift in focus in the computational catalysis and machine learning communities towards other metrics such as synthesizability, stability, lifetime or affordability.

Among van der Waals crystals, transition metal trihalide VI3 has driven attention for its magnetic and orbital properties. However, its chemical instability under ambient conditions make its exploitation challenging for technological implementation. In this context, here we show how synchrotron radiation soft X-rays partially restore stoichiometric chemical and electronic properties of VI3 crystals. By combining X-ray absorption and X-ray photoemission spectroscopies, we show as-cleaved and aged (in ultra-high vacuum conditions) chemical degradation of VI3 crystal surface, with the formation of vanadates, and its, at least partial, recovery under high-flux soft X-ray beam exposure, revealing that superficial hygroscopic contamination couples relatively weakly to the crystal surface.

Integrating magnetic order to moiré superlattices is of significant scientific and technological interest. Based on first-principles calculations, we study the interplay of magnetic proximity and moiré proximity in WSe2/WSe2/CrI3 trilayers with different stackings and twist angles. Large valley splitting is observed due to redistribution of the exciton charge density across layers via a super-exchange-like mechanism, and its electric-field dependence bears similarity to electrically tunable and valley-selective Feshbach resonances. The valley splitting can be magnified in moiré superlattices owing to the superposition of Umklapp excitons folded from moiré minibands, yielding spatially modulated and enhanced magnetic proximity. The moiré proximity effect is demonstrated via an imprinted moiré potential on CrI3 layer and its feedback to the direct moiré potential on WSe2 bilayers is observed. The cooperation between the direct and imprinted moiré potentials is shown to yield novel topological and correlated states.

We investigate the stabilization of topological Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) phases, with a specific emphasis on the intraband FFLO phase, in a one-dimensional (1D) Fermi gas subjected to an external magnetic field. This research highlights the crucial role of the interplay between Rashba spin-orbit coupling (RSOC) and Dresselhaus spin-orbit coupling (DSOC). Employing a Fermi-Hubbard model alongside the density matrix renormalization group (DMRG) method, we examine the combined effects of RSOC and DSOC on these exotic superfluid phases, taking into account attractive fermionic interactions. Our principal finding reveals that while RSOC primarily stabilizes conventional zero-momentum pairing, DSOC performs a distinct and crucial role in selectively stabilizing the intraband FFLO phase. This stabilization is achieved by enhancing spin polarization within a single helicity band and suppressing interband coherence, thereby facilitating the formation of finite-momentum FFLO pairs within the same band and resulting in the emergence of a topologically nontrivial superfluid. This targeted control of intraband FFLO pairing paves the way for new strategies in the manipulation of superfluid phases in spin-orbit coupled systems and offers essential insights for experimental realizations in ultracold atomic gases, with implications for topological quantum computing and Majorana fermions.

Predicting the glass-forming ability (GFA) of chemical compositions remains a fundamental challenge in materials science, especially for oxide glasses with broad compositional diversity. Traditional empirical and thermodynamic approaches often fail to capture the complex, nonlinear factors governing vitrification. In this study, we applied two ensemble machine learning algorithms-Random Forest (RF) and Extreme Gradient Boosting (XGB)-to the glass_ternary_hipt dataset to predict the GFA of ternary oxide glasses directly from composition-derived descriptors. Both models achieved excellent predictive accuracy (R^2 > 0.92, MAE < 0.04), confirming that GFA is learnable from compositional features alone. Feature importance analysis revealed that electronegativity variance, atomic size mismatch, and valence electron descriptors are the most influential factors, while cohesive energy and ionic radius provided secondary contributions. These chemically interpretable features align with established theories of glass formation, thereby bridging predictive performance with physical understanding. The novelty of this work lies in systematically extending ML-based predictive modeling to ternary oxide glasses, a class less studied compared to metallic and binary systems. Our results demonstrate that ensemble learning not only enables accurate GFA prediction but also provides actionable insights for designing new glass compositions with enhanced stability.

BaMg2Bi2 is a Dirac semimetal characterized by a simple Dirac cone crossing the Fermi level at the center of the Brillouin zone, protected by C3 rotational symmetry. Together with its Sr-based analogue SrMg2Bi2, it has been proposed as a promising candidate for a chemically driven topological switch: while SrMg2Bi2 is an insulator, BaMg2Bi2 exhibits non-trivial topological features. A detailed understanding of its electronic structure is essential to elucidate its electronic and transport properties. Previous photoemission studies confirmed the Dirac nature of BaMg2Bi2, but were limited to high photon energies, which hindered direct comparison with density functional theory calculations (DFT), due to reduced resolution and higher-frequency matrix-element modulation in that regime. In this work, we combine high-resolution angle-resolved photoemission spectroscopy (ARPES) and DFT calculations to get full insight on the valence band states, providing a comprehensive picture of the low-energy electronic structure. Our measurements reveal the presence of previously unobserved surface states. We found that they are topologically trivial, but they unlock a more comprehensive understanding of the material's behavior, reconciling previous discrepancies between experiment and theory.

The observation of reversible de-mixing phenomena in mixed-halide perovskites under illumination is one of the most challenging as well as intriguing aspects of this class of materials. On the one hand, it poses critical constraints to the compositional space that allows reliable design of absorbers for perovskite photovoltaics. On the other hand, it holds potential for the development of novel optoionic devices where an ionic response is triggered via optical stimuli. Funda-mental questions about the origin of such photo de-mixing process remain unanswered, both in terms of its mechanism as well as thermodynamic description. Here, we relate in-situ measurements of ionic and electronic transport of mixed bromide-iodide perovskite thin films performed during photo de-mixing with the evolution of their optical and morpho-logical properties. The results point to the definition of different stages of the de-mixing process which, based on micros-copy and spectroscopic measurements, we assign to regimes of spinodal decomposition and nucleation of quasi-equilibrium iodide- and bromide-rich phases. Combined with density functional theory calculations, we explore the role of dimensionality in the mechanism and reversibility of photo de-mixing and dark re-mixing processes, referring to elec-tronic and ionic contributions to the de-mixing driving force. Additionally, our data emphasizes the role of the surface, as significantly different de-mixing dynamics, in terms of extent and reversibility, are observed for films with or without encapsulation. Our comprehensive analysis of transport, phase and optical properties of mixed-halide perovskites pro-vides guidelines for future materials design as well as for the more general fundamental understanding of light-induced ionic phenomena.

In this paper we study magnetoelectric effects in two-dimensional magnetic bilayers and introduce the notion of a layer dipole magnetoelectric polarizability. This magnetoelectric polarizability describes the magnetization response to an applied electric field perpendicular to the bilayer. As such, it represents the electric analog of the spin magnetoelectric polarizability, governing the charge polarization response to an applied Zeeman field. Starting from the orbital magnetization produced by a perpendicular displacement field, we derive a microscopic expression for the layer dipole magnetoelectric polarizability and apply it to two minimal models for bilayer magnets, i.e., a buckled square lattice model and a magnetic topological insulator model. In the case of the buckled square lattice model we show that the layer dipole magnetoelectric polarizability has a (quasi-)topological contribution, revealing a topological magnetoelectric response of two-dimensional antiferromagnets associated with the layer pseudospin degree of freedom.

Abrikosov vortices in type-II superconductors critically influence current flow and coherence, thereby imposing fundamental limits on superconducting quantum technologies. Quantum circuits employ superconducting elements at micro- and mesoscopic scales, where individual vortices can significantly impact device performance, necessitating investigation of vortex entry, motion, and pinning in these constrained geometries. Cavity-optomechanical platforms combining flux-tunable microwave resonators with superconducting nanomechanical elements offer a promising route to the single-photon strong-coupling regime and enable highly sensitive probing of the mechanical degree of freedom under elevated magnetic fields. Here, we exploit this platform to investigate vortex entry processes at the single-event level. We observe discrete jumps of the mechanical resonance frequency attributable to individual vortex entry, corresponding to attonewton-scale forces and allowing quantitative extraction of single-vortex pinning energies. These signatures are superimposed on a smooth power-law background characteristic of the collective Campbell-regime of vortex elasticity. Our results establish optomechanics-inspired sensing as a powerful method for exploring fundamental superconducting properties and identifying decoherence pathways in quantum circuits. Beyond advancing vortex physics, this work opens new opportunities for integrating mechanical sensing into superconducting device architectures, bridging condensed matter physics and quantum information science.

We study the distinctive features of the interplay between the interlayer superconductivity and ferroelectricity in van der Waals heterostructures. Corresponding analysis is carried out within the framework of the quasiclassical Eilenberger equations for a tunnel coupled bilayer with inhomogeneous relative shift of the conduction bands between the layers, which describes the net charge transfer in sliding ferroelectrics. It is shown that the critical temperature of the interlayer superconductivity can be significantly enhanced for superconducting nuclei localized in the vicinity of ferroelectric domain walls. We demonstrate that the increase in the tunneling amplitude leads to the decrease (increase) in the difference between the critical temperatures for localized and homogeneous superconducting states for the spin-singlet (spin-triplet) interlayer superconductivity. We also perform an extensive analysis of the effects of the in-plane magnetic field on the interlayer superconductivity. It is shown that the orbital effect can result in the suppression of the spin-singlet interlayer superconductivity and to the enhancement of the spin-triplet one. We find that possible manifestations of the paramagnetic effect include the suppression of the interlayer superconductivity by rather weak Zeeman fields, the two-fold anisotropy of the critical magnetic field for the spin-triplet states as well as the appearance of the reentrant superconducting phases. It is shown that the joint influence of the orbital and paramagnetic mechanisms on the spin-triplet interlayer superconductivity can even lead to a nonmonotonic behavior of the superconducting critical temperature as a function of the external magnetic field. The obtained results are discussed in the context of recent experimental data on van der Waals structures with coexisting superconductivity and sliding ferroelectricity.

In this paper we predict that the magnetoelectric response of two-dimensional (2D) antiferromagnets is determined by the topology of the ground state. This topological magnetoelectric response, encoded in the spin magnetoelectric polarizability and its closely related spin multipolization, occurs when the electronic structure of the antiferromagnetic insulator is described by massive 2D Dirac fermions, and is therefore native to 2D, unlike the topological magnetoelectric effect of three-dimensional topological insulators. To demonstrate the topological contribution to the (spin) magnetoelectric polarizability, we compute the magnetoelectric polarizability microscopically for two distinct minimal lattice models: a spin-orbit coupled Néel antiferromagnet and a spin-orbit-free noncollinear antiferromagnet with double-$Q$ spin order. We show that the topological origin of the revealed magnetoelectric effect can be traced back to the electromagnetic response of topological semimetals in two dimensions, and hence is ultimately governed by a strong topological invariant in one dimension. Given this dimensional hierarchy, we further consider two minimal lattice models in one dimension, both one-dimensional variants of the 2D lattice models, and show that the magnetoelectric polarizability exhibits a clear signature of nontrivial crystalline topology. Possible material realizations are discussed.

The timing of reproduction is crucial for biological fitness. Reproductive delays carry an inherent demographic cost: an individual that takes longer to reproduce contributes later to population growth, a priori, without any compensating benefit. However, natural selection favors delayed reproduction under certain environmental conditions, a phenomenon that remains poorly understood. Here, we investigate how the environment can determine the evolution of particular life histories using a parsimonious delayed-logistic model. Individuals become reproductive only after a fixed lag whereas birth rates fluctuate under temporally correlated stochasticity. Numerical integration, analytical calculations and evolutionary simulations reveal that the joint effect of demographic memory and colored multiplicative noise generate a strongly nonmonotonic dependence of fitness on life history, with three distinct regimes of population performance: rapid reproduction maximizes linear growth but amplifies fluctuations and extinction risk; delayed reproduction buffers environmental variability, substantially increasing mean extinction times despite slower growth; strikingly, and central to our results, there is a broad band of maladaptive intermediate life histories that simultaneously reduce both growth and persistence, an effect that arises generically from the mismatch between reproductive timing and environmental autocorrelation. Our results show that reproductive timing is not merely a life-history parameter but an adaptive mechanism tuned to environmental time scales, and that "dangerous middle" maturation times can be inherently disfavored, with implications for understanding reproductive strategies across the tree of life.

$\alpha$-Li$_3$PS$_4$ is a promising solid-state electrolyte with the highest ionic conductivity among its polymorphs. However, its formation presents a thermodynamic paradox: the $\alpha$-phase is the equilibrium phase at high temperature and transforms to the stable $\gamma$-Li$_3$PS$_4$ polymorph when cooled to room temperature; however, $\alpha$-Li$_3$PS$_4$ can be synthesized and quenched in a metastable state via rapid heating at relatively low temperatures. The origin of this synthesizability and anomalous stability has remained elusive. Here, we resolve this paradox by establishing a comprehensive time-temperature-transformation (TTT) diagram, constructed from a computational temperature-size phase diagram and experimental high-time-resolution isothermal measurements. Our density functional theory calculations reveal that at the nanoscale, the $\alpha$-phase is stabilized by its low surface energy, which drastically lowers the nucleation barrier across a wide temperature range. This size-dependent stabilization is directly visualized using in-situ synchrotron X-ray diffraction and electron microscopy, capturing the rapid nucleation of nano-sized $\alpha$-phase and its subsequent slow transformation. This work presents a generalizable framework that integrates thermodynamic and kinetic factors for understanding nucleation and phase transformation mechanisms, providing a rational strategy for the targeted synthesis of functional metastable materials.

We develop a microscopic theory of magnon-exciton drag effect in a bilayer van der Waals antiferromagnetic semiconductor CrSBr. Effective exciton-magnon coupling arises from an orbital mechanism: Magnons tilt the layer magnetizations, enabling charge carrier tunneling that mixes intra- and interlayer excitons and thereby modulate the exciton energy. We derive the effective Hamiltonian of exciton-magnon coupling, based on our calculation of the magnon spectrum taking into account short-range exchange interaction between Cr-ion spins, single-ion anisotropy, and long-range dipole-dipole interactions. The latter produces a negative group velocity of magnons at small wavevectors. We show that despite rather small renormalization of exciton's energy and effective mass by the exciton-magnon interaction, the three key two-magnon processes: exciton-magnon scattering, two-magnon absorption by exciton, and two-magnon emission are highly efficient. By solving the Boltzmann kinetic equation, we evaluate short exciton-magnon scattering time which is in the sub-ps range and strongly decreases with the increase of magnon population. Hence, exciton-magnon scattering is likely to be dominant over other scattering processes related to the exciton-phonon and exciton-disorder interactions. We demonstrate that magnons can efficiently drag excitons, resulting in a large and nearly isotropic exciton propagation that can significantly exceed the intrinsic anisotropic diffusion. Our results provide a theoretical basis for recent observations of anomalous exciton transport in CrSBr [F. Dirnberger, et al., Nat. Nano. (2025)] and establish magnon-exciton drag as a powerful mechanism for controlling exciton propagation in magnetic systems.

Two-dimensional (2D) materials have been proposed, among many other applications, as a efficient tool for the separation of atomic and molecular species and their corresponding isotopes, given the confinement provided by their subnanometric dimensions. In this work we present three dimensional quantum wave packet calculations revealing an enhancement in the quantum transport in bilayer over monolayer graphdiyne membranes, one of the most popular 2D materials which is commonly employed for this purpose. Besides, resonances emerge superimposed over the typical monolayer profile for transmission probabilities, a feature that is general to other bilayer nanoporous 2D heterostructures and that shows a strong dependence on the interlayer separation.

Molecular dynamics (MD) simulations have become indispensable for exploring tribological deformation patterns at the atomic scale. However, transforming the resulting high-dimensional data into interpretable deformation pattern maps remains a resource-intensive and largely manual process. In this work, we introduce a data-driven workflow that automates this interpretation step using unsupervised and supervised learning. Grain-orientation-colored computational tomograph pictures obtained from CuNi alloy simulations were first compressed through an autoencoder to a 32-dimensional global feature vector. Despite this strong compression, the reconstructed images retained the essential microstructural motifs: grain boundaries, stacking faults, twins, and partial lattice rotations, while omitting only the finest defects. The learned representations were then combined with simulation metadata (composition, load, time, temperature, and spatial position) to train a CNN-MLP model to predict the dominant deformation pattern. The resulting model achieves a prediction accuracy of approximately 96% on validation data. A refined evaluation strategy, in which an entire spatial region containing distinct grains was excluded from training, provides a more robust measure of generalization. The approach demonstrates that essential tribological deformation signatures can be automatically identified and classified from structural images using Machine Learning. This proof of concept constitutes a first step towards fully automated, data-driven construction of tribological mechanism maps and, ultimately, toward predictive modeling frameworks that may reduce the need for large-scale MD simulation campaigns.

We show theoretically that weak quantum fluctuations induced by a non-symmetric electromagnetic environment may lead to a quantized transconductance of a multi-terminal quantum contact rather than to a blockade of transport in the contact. The result suggests the possibility to realize Quantum Hall phenomenology without its common ingredients and/or a topological quantum state.

The Rashba spin-orbit coupling (SOC) is a well-known mechanism for the spin-charge interconversion via the inverse and direct spin galvanic effects. The lack of a full inversion symmetry allows the coupling of the charge current and spin density. In this paper we investigate this phenomenon when the in-plane rotational symmetry is lowered to the $C_{2v}$ and $C_{3v}$ symmetry groups, whereby the electron spectrum becomes anisotropic. We find that in the $C_{2v}$ case, depending on the ratio between the Rashba SOC strengths along the principal axes, the non-equilibrium spin density deviates notably from the $90^o$ degrees rotation, with respect to the applied electric field, familiar in the isotropic case. In the $C_{3v}$ case, when a warping cubic-in-momentum term is present, whereas the standard $90^o$ degrees rotation of the spin density remains, the spin-charge interconversion depends on the intensity of the warping itself. The microscopic theory takes into account disorder including vertex corrections, both via the diagrammatic implementation of the Kubo formula and via the quantum kinetic theory. We show that vertex corrections are crucial to capture the details of the inverse spin galvanic effect in contrast to previous treatments based on the constant broadening approximation.

Two-dimensional ferroelectrics have recently emerged as a promising avenue for next-generation optoelectronic and photovoltaic devices. Due to the intrinsic absence of inversion symmetry, 2D ferroelectrics exhibit bulk photovoltaic effect (BPVE), which relies on hot, non-thermalized photo-excited carriers to generate a photo-induced current with enhanced performances thanks to efficient charge separation mechanisms. The absence of a required p-n junction architecture makes these materials particularly attractive for nanoscale energy harvesting. Recent studies have reported enhanced BPVE in nanometer-thick CuInP$_2$S$_6$ ferroelectric embedded between two graphene wafers, driven by relatively strong polarization and reduced dimensionality. Short circuit photocurrent density values have been observed to reach up to mA/cm$^2$. In this paper, we demonstrate that the shift-current mechanism alone cannot fully account for these high conductivity values, suggesting that additional mechanisms may play a significant role. Furthermore, our work confirms the existence of a strong size effect, which drastically reduces the shift-conductivity response in the bulk limit, in agreement with experimental observations.

Quantum confinement not only reshapes electronic states but also reorganizes the vibrational landscape of low-dimensional semiconductors. In halide perovskites, however, the role of confinement in governing symmetry effects on vibrational modes has remained unresolved. Here we synthesize 2D CsPbBr3 nanoplatelets with atomically defined thicknesses for 2-5 monolayers (MLs) and perform exciton absorption and emission analysis, crystalline phase determination, and phonon analysis. The lowest dimensional structure (2 MLs) reveal a co-existence of cubic and orthorhombic structure, energetically converging to orthorhombic for 3 MLs and beyond. Through polarization-resolved Raman spectroscopy and first-principles theory for 2-5 MLs, a striking symmetry contrast is found: B1g modes intensify and evolve in line with the phonon-confinement model, while Ag modes deviate, reflecting their distinct spatial localization. First principles calculations show that B1g vibrational modes largely reside in the xy-plane, Pb-Br-Pb units connect octahedra along the xy-direction with increased lattice dynamics as inner layers accumulate, whereas A1g vibrations couple to out-of-plane distortions and remain susceptible to surface disorder and finite-size effects. This symmetry-driven dichotomy provides a general framework for understanding phonon localization in layered halide perovskites. Beyond mechanism, we establish Raman fingerprints, particularly the A1g/B1g intensity ratio in cross-polarized geometry, as a calibrated, non-destructive metrology for 2D nanoplatelet thickness through 2-5 MLs. These results bridge electronic and phonon confinement and highlight symmetry engineering as a route to understand and control phonons, excitons, and their interactions in low-dimensional optoelectronic materials.