Materials Science
Divergent Solid-state Conversion Pathways in Evaporated All-perovskite Tandem Solar Cells
Huagui Lai, Amber Wright, Nick Huber et al. (+8 more)
Sequential thermal evaporation (sTE) is emerging as a solvent-free route to high-quality mid-bandgap perovskites, but its extension to mixed-halide wide-bandgap (WBG) and Sn-Pb narrow-bandgap (NBG) absorbers for all-perovskite tandem solar
cells (TSCs) remains limited by an incomplete understanding of solid-state conversion. Here, using time-sliced ex situ analysis, we reveal divergent solid-state conversion mechanisms in sequentially evaporated WBG and NBG precursor stacks. In WBG stacks, formamidinium (FA)-containing species penetrate the inorganic template and Br/I redistribution precedes substantial three-dimensional perovskite formation. The photoactive phase then crystallizes from a chemically mixed reservoir, and absolute PbBr$_2$ thickness, rather than nominal PbBr$_2$/PbI$_2$ ratio, determines the final bandgap. In NBG stacks, by contrast, an early Pb-rich perovskite phase forms upon formamidinium iodide deposition, restricting further FA penetration into the buried SnI$_2$ precursor. Subsequent annealing promotes rapid
lattice reorganization faster than Sn/Pb interdiffusion, leaving vertical compositional gradients. Guided by these insights, we develop sTE absorbers with bandgaps spanning 1.26-1.96 eV and demonstrate the first evaporated all-perovskite TSC, reaching a power conversion efficiency of 19.2%. Encapsulated tandems retain on average 80% of their initial efficiency after 1,200 h at 65 $^\circ$C (ISOS-D-2). These results establish bandgap-specific control of solid-state conversion as a design principle for sequentially evaporated perovskite tandem photovoltaics.
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All authors Huagui Lai, Amber Wright, Nick Huber, Niels Uythoven, Federico De Giorgi, Jincheng Luo, Tristan Sachsenweger, Sunil B. Shivarudraiah, Chih-Jen Shih, Wolfgang Tress, Fan Fu
Mesoscale and Nanoscale Physics
Plasmons in twisted bilayer graphene across dispersive and flat bands
Antonio Palamara, Michele Pisarra and Antonello Sindona
The dynamical dielectric response of twisted bilayer
graphene is explored in large-angle dispersive-band and small-angle quasi-flat-band regimes using time-dependent density-functional theory within the random-phase approximation. At the reference bilayer-
graphene interlayer distance, weak coupling in the largest-angle structures preserves Dirac dispersions and the intrinsic $\pi$ plasmon. Electron doping activates a two-dimensional Dirac plasmon with energies obeying approximate
geometric twist-angle scaling, while acoustic-like branches remain embedded in the single-particle continuum. The prohibitively large first-magic-angle supercell is represented by a tractable
cell with its interlayer separation reduced to the angle-dependent magic distance, where four quasi-flat bands emerge around the Fermi level. Their partial occupation produces a dispersive low-energy plasmon-like excitation without a clear dielectric zero at resonance. A distinct interband plasmon is instead identified, supported by transitions involving the quasi-flat
manifold and neighboring high-density-of-states regions. Band-energy rescaling places its characteristic energy in the mid-infrared range of interband collective excitations measured near the magic angle.
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Statistical Mechanics
Landau diamagnetism and the de Haas-van Alphen effect from a single geometric construction
Sung-Hoon Lee
Landau diamagnetism is usually derived from the grand canonical potential, a calculation that yields the correct susceptibility but little physical insight, while the rule that extremal cross sections govern the de Haas-van Alphen (dHvA) oscillations is commonly asserted rather than exhibited. We present an elementary zero-temperature construction in which the occupied states of a free-electron gas are grouped, interval by interval along the field direction, into the Landau levels onto which they condense. Within each interval the field-induced energy cost reduces to a transfer of states between two congruent triangles, and center-of-mass arithmetic yields the Landau susceptibility. The construction fails only in a narrow neighborhood of an extremal cross section of the Fermi surface; there the contribution oscillates with the dHvA period, one oscillation for each Landau level that passes through the extremal cross section. Direct zero-temperature state counting locates the oscillation: the residual is concentrated in the few intervals nearest the extremal cross section, the summed contribution of the distant ones being negligible on the scale of the peak oscillation amplitude.
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Statistical Mechanics
Higher-Order Interactions in Complex Systems: Mechanisms, Behaviour, Representation and Reducibility
Francisco J. Pérez-Reche
Higher-order interactions couple three or more elements in ways that cannot be decomposed into pairwise contributions. In diverse complex systems they produce striking collective behaviours such as explosive synchronization, discontinuous transitions and altered stability. Neither such behaviour nor a description written in many-body terms establishes a many-body mechanism, since both depend on how the system is represented. This review distinguishes three questions: what mechanism governs the system, what behaviour does it produce, and how is either represented? Representation covers both which variables are included and how relations among them are encoded. We examine direct many-body mechanisms, nonlinear but pairwise mechanisms that mimic them, and indirect routes through shared environments or eliminated variables, together with temporal aggregation, an artefact of observation rather than a mechanism. The same behaviour can arise from different mechanisms, and a given higher-order mechanism has no universal behavioural consequence. We then formulate reducibility, the question of whether a higher-order model can be replaced by a lower-order one, as a comparison between a source model and an admissible class of lower-order models, relative to a target and a tolerance. The target may be a microscopic rule, an observable or a qualitative feature. Information-theoretic and inferential methods are reviewed as complementary tools for detecting higher-order dependence, testing lower-order alternatives and reconstructing interaction structure. However, observational data alone generally cannot establish the mechanism. We close by identifying open problems in linking mechanisms to measurable signatures, coarse-graining, identifiability and causality, and in extending reductions beyond mean field. (Abridged)
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Materials Science
Coherent antiferromagnetic resonance in MnO driven by impulsive terahertz excitation
Yinchuan Lv, Martin J. Cross, Hari Paudyal et al. (+4 more)
Antiferromagnets (AFMs) offer a promising platform for ultrafast information processing owing to their intrinsically fast
spin dynamics and vanishing net magnetization. Realizing this potential, however, requires understanding how terahertz fields excite coherent
magnons and how the resulting
spin motion is transduced into an optical signal. Here we report impulsive terahertz (THz) excitation and time-domain detection of the antiferromagnetic resonance (AFMR) in single-
crystal manganese(II) oxide. Time-resolved birefringence measurements reveal long-lived coherent
spin oscillations in the AFM phase. The resonance softens and becomes strongly damped upon warming toward the Néel temperature. Despite this similar excitation behavior, the detected birefringence in MnO is markedly weaker than in NiO. We associate this suppressed optical visibility with the weak
spin–orbit-mediated magneto-optical coupling of orbital-singlet, high-
spin Mn$^{2+}$. These results demonstrate that coherent
magnon excitation and its optical detection are governed by distinct microscopic interactions.
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All authors Yinchuan Lv, Martin J. Cross, Hari Paudyal, Christopher T. Parzyck, A. H. M. Reid, Durga Paudyal, Matthias C. Hoffmann
Superconductivity
Type-I superconductivity in a quasi-2D topologically nontrivial YbBi$_2$
Karolina Górnicka, Sudip Malick, Joanna Bławat et al. (+13 more)
Intrinsic superconductivity in stoichiometric materials with nontrivial electronic
topology remains uncommon, limiting opportunities to investigate how these two phenomena coexist within a single electronic system. Here, we report bulk type-I superconductivity below $T_c$ $\sim$ 0.9~K in YbBi$_2$, a layered rare-earth compound with a nonsymmorphic
crystal structure and a quasi-two-dimensional Fermi surface. Thermodynamic and transport measurements establish the superconducting ground state, while
quantum oscillations reveal exceptionally light carriers, with a cyclotron mass as low as 0.07 $m_e$, and a nonzero Berry phase of approximately 0.82 $\pi$. The latter closely matches the calculated value of the corresponding Wilson phase 0.99 $\pi$ for the corresponding orbit near a
symmetry-protected band degeneracy. ARPES measurements show good agreement with key features of the calculated electronic structure, providing complementary experimental constraints on the normal-state band structure. The combination of intrinsic type-I superconductivity, light quasi-two-dimensional carriers, and signatures of nontrivial electronic
topology identifies YbBi$_2$ as a distinct stoichiometric platform for investigating superconductivity in a topologically nontrivial electronic environment.
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All authors Karolina Górnicka, Sudip Malick, Joanna Bławat, Michał Modrzejewski, Hanna Świątek, Michał J. Winiarski, Federico Mazzola, Ivana Vobornik, Chiara Bigi, Jacob Cook, Brenden R. Ortiz, Andrew F. May, Andrzej P. Kądzielawa, John Singleton, Bartlomiej Wiendlocha, Tomasz Klimczuk
Strongly Correlated Electrons
When Is Kramers-Wannier Duality Invertible?
Akash Sinha, Pramod Padmanabhan and Vladimir Korepin
Kramers-Wannier duality of the
quantum Ising chain is naturally realized as a noninvertible transformation on a finite periodic chain. Upon incorporating appropriate
symmetry-twisted sectors, however, the duality can be promoted to an invertible
unitary transformation. In this Letter, we classify when the Kramers-Wannier duality admits an invertible realization on a finite
Hilbert space. We show that this is determined by the representation of the Ising bond
algebra and establish a necessary and sufficient condition in terms of its two central elements. This representation-theoretic criterion unifies the conventional noninvertible realization with invertible constructions involving
symmetry-twisted sectors and applies equally to other models with the same underlying bond
algebra. As an explicit example, we find an order-disorder duality in a non-trivial realization of the Ising bond
algebra that admits an invertible Kramers-Wannier duality.
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Materials Science
Modeling Dynamic Magnetic Response of Spinel Soft Ferrites with the Steepest-Entropy-Ascent Quantum Thermodynamics Formalism
Deepak Dhariwal, William T. Reynolds Jr. and Michael R. von Spakovsky
Selecting soft ferrites for alternating-field applications requires balancing
magnetic response, dissipation, nonlinearity, and heating. We use a field-driven steepest-
entropy-ascent
quantum thermodynamic (SEAQT) model to compare the electron,
phonon, and
magnon responses of Fe$_3$O$_4$, MnFe$2$O$4$, and (Mn${0.5}$Zn${0.5}$)Fe$_2$O$_4$ within a common first-principles framework. The model treats spatially uniform longitudinal relaxation and neglects domain-wall motion, transverse rotation, resonance, eddy-current effects, and heat removal. We use $\tau_e=0.05$ ps and $\tau_p=3$ ps for all three materials, with effective longitudinal
magnon relaxation times of 500, 200, and 85 ps, respectively; these literature-motivated values are model inputs, not fits to measured losses. Within this framework, the Mn–Zn ferrite gives the largest peak longitudinal magnetization change, retains its response best at high frequency, and shows the largest work per cycle and peak-to-peak
magnon temperature change, whereas MnFe$_2$O$_4$ gives the largest normalized $\chi''$ peak. Thus, no single ferrite ranks highest across all metrics: the preferred material depends on the property, frequency, field amplitude, and cation configuration of interest. The model therefore provides a spectrum- and kinetics-resolved screening tool for engineering comparison of ferrites rather than a prediction of total core loss.
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Statistical Mechanics · Cross-listed from quant-ph
Semiclassical scaling of eigenstate thermalization in single-particle chaotic systems
Yaoqi Ye and Xiao Wang
We study the off-diagonal
matrix elements of real-space observables in time-reversal-invariant single-particle chaotic systems. By analyzing the semiclassical expression for the off-diagonal variance derived from Berry's
conjecture, we show that the banded structure of the observable
matrix emerges naturally. For local observables, we identify a characteristic bandwidth associated with a late-time timescale inversely proportional to the particle velocity. We further show that, for systems with steep-wall confinement, the predicted magnitude follows the
entropy scaling of the eigenstate thermalization hypothesis (ETH), multiplied by an additional kinetic-energy-dependent factor that is independent of spatial dimension and is not captured by conventional many-body ETH. We illustrate these results through a case study of
quantum billiards and verify the semiclassical scaling numerically in a generalized quarter-Sinai billiard. Our results elucidate the dynamical implications of Berry's
conjecture and provide a comparison between single-particle eigenstate thermalization and many-body ETH.
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Mesoscale and Nanoscale Physics
Highly uniform first-electron position in qubit arrays fabricated on dedicated QSOI(R) 300mm commercial platform
Johan Pelloux-Prayer, Elise Prin, Giselle A. Elbaz et al. (+11 more)
We report progress toward the development of a
quantum silicon-on-
insulator (QSOI(R)) technology compatible with 300mm CMOS fabrication and adapted from the 28nm Fully-Depleted SOI (28nm FD-SOI) platform for scalable
quantum computing. We compare
quantum devices fabricated with standard 28nm FD-SOI and QSOI(R) technologies, and show striking improvements of room temperature electrostatic properties of the individual device. Moreover, the QSOI(R) technology has significantly reduced the device variability and the dispersion of device properties at the wafer level. Transistor metrics are reproduced by TCAD simulations showing that the electrostatics of the devices behave as expected for QSOI(R) technology. Wafer-scale measurements at sub-2K show reproducible
quantum dots down to the few-electron regime with 69% yield for successful charge detection of the first electron and a dispersion of the first electron position of $\mathrm{\pm 35 mV}$ over 377
quantum dots. These results establish QSOI(R) as a promising platform for CMOS-compatible
quantum device co-integration.
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All authors Johan Pelloux-Prayer, Elise Prin, Giselle A. Elbaz, Pierre-Louis Julliard, Amaryllis Comiti, Clément Nguyen, Sylvain Martin, Patrick Torresani, Renan Lethiecq, Carlos Augusto Suarez Segovia, Franck Arnaud, Etienne Nowak, Tristan Meunier, Bruna Cardoso Paz
Disordered Systems and Neural Networks · Cross-listed from physics.soc-ph
When higher-order interactions matter: reducibility, parsimony, and microscopic organization
Alex Arenas, Federico Battiston and Andrea Gabrielli
The current debate on higher-order interactions raises a fundamental question: when can systems organized through group interactions be faithfully represented within a graph-based formalism? Recent results show that graph descriptions can reproduce higher-order dynamics exactly or preserve selected macroscopic observables. Yet reducibility does not necessarily imply simplification, as information removed from the interaction structure may reappear as complexity in the effective dynamics, while structural features such as nestedness, heterogeneity, and cross-order correlations may be obscured by the reduction. We argue that formal representability alone is insufficient as a criterion for model choice. Both "simpler" and "equivalent" are question-dependent notions: parsimony must be assessed for the complete structure-dynamics model, and adequacy must be defined relative to the observables, scales, and regimes required by the scientific question. A reduced model may therefore be fully adequate for locating a phase transition or identifying a universality class while being inadequate for reproducing microscopic trajectories, transient dynamics, or structure-function relations. When group structure carries relevant microscopic information, higher-order representations may remain the most direct, interpretable, and parsimonious description, as well as the natural framework for understanding how microscopic organization gives rise to macroscopic behavior and functionality.
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Quantum Gases
Statistical delocalization in the Anyonic Aubry-André model
Andoni Agirre, André Eckardt and Tobias Grass
Many-body localization is remarkable in that localization persists despite the presence of dynamical interactions. Here we demonstrate the converse phenomenon: enhanced many-body delocalization induced solely by exchange statistics. We study a Aubry-André quasiperiodic system of anyons in one dimension in the absence of density-density interactions. In terms of anyon operators, the system is described by a quadratic
Hamiltonian. By analyzing the finite-size scaling of its spectral properties and the inverse participation ratio of many-body eigenstates, we find that increasing the anyonic statistical phase systematically shifts the many-body localization crossover toward larger quasiperdiodic potentials. We further confirm these findings using a dynamical probe, namely the persistence of an initial density imbalance following quenches. Our results establish exchange statistics as an independent mechanism capable of altering many-body localization, revealing a fundamentally distinct route to delocalization in one-dimensional
quantum systems.
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Strongly Correlated Electrons
Corner entanglement scaling with projected entangled pair states
Chloé Van Bastelaere, Rui-Zhen Huang and Laurens Vanderstraeten
Entanglement scaling provides a powerful probe of universal properties at
quantum critical points. In two dimensions, contributions originating from a corner-shaped bipartition exhibit a universal scaling, which is determined by the underlying conformal field theory. We develop a method to extract this corner
entanglement entropy from projected entangled pair states directly in the thermodynamic limit. When applied to models at a
quantum critical point, we show that the corner contribution exhibits scaling with the effective correlation length, in agreement with the hypothesis of finite-
entanglement scaling. Our results for the corner coefficients are consistent with other methods, demonstrating the efficiency of our method for diagnosing strongly-correlated
quantum critical points in two dimensions.
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Materials Science
Anharmonic Phonon Renormalization and Defect Tolerance of the Thermoelectric Power Factor in Monolayer SnSe
Nguyen Tran Gia Bao, Thang Bach Phan, Vu Thi Hanh Thu et al. (+1 more)
Monolayer tin selenide (SnSe) exhibits phase-dependent anharmonic
lattice dynamics, yet their consequences for the thermoelectric power factor (PF) and point-defect tolerance remain unresolved. We combine density functional theory, the
stochastic self-consistent harmonic approximation (SSCHA), and Boltzmann transport calculations including electron-
phonon and electron-defect scattering to investigate monolayer $\alpha$-SnSe (Pnma) and $\beta$-SnSe (Cmcm). In dynamically stable $\alpha$-SnSe, SSCHA renormalizes the finite-temperature
phonons without changing the qualitative n-type transport picture. In $\beta$-SnSe, SSCHA removes the harmonic soft-mode instability of the Cmcm phase at 800-1000 K, and thereby enables high-temperature transport calculations; LO/TO-2 is the principal electron-scattering channel. In the lower-density window near $10^{12}$ cm$^{-2}$, the n-type PF reaches 15-19 $\mu\mathrm{W}/(\mathrm{K}^{2}\cdot\mathrm{cm})$ at 800-900 K and exceeds the p-type PF primarily because of the higher electrical conductivity. Se vacancies ($V_{\mathrm{Se}}$) produce weaker electron-defect scattering than Sn vacancies ($V_{\mathrm{Sn}}$), and p-type transport is less defect tolerant than n-type transport in both phases. We define an operational critical defect concentration, $C_{\mathrm{crit}}$, at which the PF decreases by 15% relative to the corresponding defect-free value. The lowest $C_{\mathrm{crit}}$ is $8.841\times10^{-5}$ (approximately 88 ppm) for p-type $\alpha$-SnSe with $V_{\mathrm{Sn}}$; for n-type $\beta$-SnSe with $V_{\mathrm{Se}}$, the 15% threshold is not reached up to $5\times10^{-3}$ (5000 ppm). These results distinguish finite-temperature
phonon renormalization in stable $\alpha$-SnSe from anharmonic stabilization in $\beta$-SnSe and provide defect-concentration limits for preserving the PF.
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All authors Nguyen Tran Gia Bao, Thang Bach Phan, Vu Thi Hanh Thu, Nguyen Tuan Hung
Quantum Gases
Fragmentation of Quantum Fluid in dipolar Bose-Einstein condensate
Shivam Singh and Ayan Khan
In this article, we study the dipolar Bosonic
quantum fluid. The fluid experiences mean-field, beyond mean-field, and three body interactions. We investigate their competition with dipolar interaction and fragmentation as a result of this competition. We further investigate the elementary excitations and note two distinct dispersion regimes, namely roton-mode and modulational instability. We support our observation by calculating the superfluid fraction and the condensate fraction.
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Statistical Mechanics
Encounter Propagator for Multiple Targets: A Dirichlet-to-Neumann Spectral Formalism
Denis S. Grebenkov
We develop an encounter-based formulation of restricted
diffusion in a bounded domain with multiple targets, resolving separately the boundary local time accumulated on each target. Unlike the single-target problem, the target projection operators do not generally commute with the governing Dirichlet-to-Neumann (DtN) operator, so that its eigenbasis does not diagonalize the local-time dependence. We overcome this difficulty by decomposing the DtN operator into target-restricted blocks. Multi-dimensional Laplace inversion then yields a convergent switching expansion, whose successive terms describe alternating diffusive transfers between the targets. We also derive an equivalent operator-valued renewal equation. For two targets, diagonalizing the target-restricted blocks provides an explicit spectral representation in terms of two DtN block spectra and an inter-target coupling
matrix. When the coupling preserves spectral modes, the switching series can be resummed exactly in terms of modified Bessel functions. In general, as the off-diagonal DtN block is smoothing for separated targets, one can resort to low-rank finite-dimensional approximations. We examine an effective two-mode reduction for small, well-separated targets and identify a regime in which repeated inter-target transfers are progressively suppressed. Probabilistic interpretations and implications for
diffusion-controlled reactions are discussed.
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Quantum Gases
Odd/Even or Half ? Entanglement Anomaly in the Bose-Hubbard model
Humberto E. López-Hernández and Santiago F. Caballero-Benitez
The area law relates the bipartite
entanglement entropy of a
quantum many-body ground state to the size of the boundary between the subsystems, but the geometry of this boundary is rarely discussed. We inspect this in the 1D Bose-Hubbard model at fixed density by comparing four spatial bipartitions of the periodic
lattice: first half, second half, even sites, and odd sites; sharing the same number of sites but differing in how the boundary is arranged. We find analytical limits with perturbation theory: in the Mott
insulator the contiguous cut obeys the area lay while the alternating cut obeys a volume law $S\propto N_s$, in this sense an anomaly, and for the superfluid both cuts colapse to the binomial saturation due to delocalization of the state. We formulate these limits as a statement about the many-body problem using a generalized slave-
boson approach based on mean-field with
quantum fluctuations while verifying with Exact Diagonalization (ED) for small
lattice sizes and Densitiy
Matrix Renormalization Group (DMRG) simulations for $N_s\gg 1$. The slave-
boson Gaussian ground state allows to compute the
entanglement entropy from a reduced correlation
matrix for any desired bipartition consistent with ED and DMRG results. Using slave
bosons the computational cost is set by the local cutoff $n_{\max}$ rather than the
Hilbert space dimension, so we can reach
lattice sizes far beyond ED. Our method is capable of establishing the partition-dependent scaling laws as a many-body feature, not only a finite-size effect, in great agreement with the ED for $N_s\in[4,10]$ and DMRG for larger
lattice sizes.
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Strongly Correlated Electrons
Tunable flat band on the surface of a rhombohedral kagome ferromagnet
Xinglu Que, Qingyu He, Lihui Zhou et al. (+5 more)
A central goal in the exploration of kagome-based materials is the realization of a flat band that has meV bandwidth and lies close to the Fermi energy. The prevailing assumption is that band flattening originates from destructive hopping processes on the kagome
lattice. We perform scanning tunneling microscopy (STM) on the layered kagome ferromagnet Fe$_3$Sn$_2$ and show that it indeed hosts a flat band near the Fermi energy, which is manifested as a sharp peak in the differential tunneling conductance. First-principles slab calculations reveal, however, that this band is flattened not by the destructive interference of intralayer hopping, but by interlayer hopping between rhombohedral-stacked kagome planes in Fe$_3$Sn$_2$, and is confined to the surface layer. This surface band, forming in the vicinity of the Brillouin zone corners $\bar{K}$ and $\bar{K'}$, exhibits rich
magnetic-field dependence, including fine structure due to valley-
symmetry breaking by rotated Fe moments, as well as a persistent diamagnetic shift associated with orbital
magnetic moments, all reproduced by our calculations. Our results, highlighting the crucial role of layer stacking on the band structure of kagome magnets, demonstrate experimentally an alternative mechanism of generating magnetically tunable flat bands in atomically thin volumes of topological magnets.
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All authors Xinglu Que, Qingyu He, Lihui Zhou, Lilian Prodan, Vladimir Tsurkan, István Kézsmárki, Hidenori Takagi, Dennis Huang
Materials Science
Machine Learning for High-Entropy Catalysts: Methods and Applications
Hao Chen, Zongrui Pei and Xianglin Liu
High-
entropy alloys (HEAs) exhibit exceptional catalytic performance in various reactions due to their high configurational
entropy, synergistic elemental effects, tunable electronic structures, and excellent structural stability. However, the vast compositional space of HEA catalysts makes traditional experimental and theoretical design costly and inefficient. In recent years, data-driven machine learning (ML) methods have emerged as powerful tools for studying HEAs in catalysis. Through predictive models and ML surrogates, researchers can decipher the intricate composition-structure-performance relationships of these materials. In addition, by leveraging large
language models (LLMs) for knowledge extraction, hypothesis generation and validation, and as a foundation to build integrated design workflows, ML approaches can significantly accelerate the design of novel HEA catalysts. This review systematically summarizes the latest methodological advances and applications of ML methods for HEAs in catalysis, discusses the challenges, and offers insights into future research directions to support the rational design and efficient development of catalysts.
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Materials Science
Orbital fingerprinting of magnetism across the Mn-Ni-Ga Heusler ternary
Felipe Hawthorne, Daniela A. Damasceno, Raphael M. Tromer et al. (+2 more)
In Mn–Ni–Ga Heusler
alloys, the competing
magnetic states are separated by differences of a few meV per atom, so the ground state has to be resolved from the electronic structure and cannot be read off the composition. Moving away from the stoichiometric compounds, where the established rules for Heusler magnetism fall short, increases this difficulty. To overcome it, we introduce orbital fingerprints taken from the projected density of states, and use them as the input to machine-learning models for classification of the
magnetic ordering, for the
magnetic moment amplitude, for the
spin polarization at the Fermi level and for interpolation of the phase diagram. The models are trained on a
dataset of 370
spin-polarized first-principles calculations of quasirandom structures covering the ternary, which show good agreement with the
magnetic ground states and
lattice parameters available in the literature. For
magnetic ordering, the top-ranked descriptor is the same quantity found by first-principles calculations to distinguish the phases, suggesting that the fingerprints capture the underlying physics.
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All authors Felipe Hawthorne, Daniela A. Damasceno, Raphael M. Tromer, Ronaldo R. Pelá, Cristiano F. Woellner
Superconductivity
Generic thermodynamics of condensates with extremely small superfluid density —Application to UTe$_2$ and hidden second phase transition—
Kazushige Machida
Motivated by recent experimental findings on UTe$_2$ via NMR and specific heat experiments, we theoretically explore the thermodynamic signatures of condensates with small superfluid density and characterize their physical properties. We identify the hidden superconducting phase $A_2$ composed of
spin-up Cooper pairs at lower temperature ($T$) and field ($H$) under ambient pressure of UTe$_2$ and show that $A_2$ reappears at higher $H$ for all three principal field directions, $a$, $b$, and $c$-axis. The phase transition lines from the $A_1$ phase with
spin down pairs to the $A_2$ phase in the $H$-$T$ plane are all horizontal in common, implying a universal physical origin due to the originating from the
magnetic-energy gain of the
spin-up pairing state with increasing
magnetic field. This multiple-phase diagram is extended to these under pressure ($P$), resulting in a simple picture based on non-
unitary spin-triplet pairing
symmetry $^3B_{3u}$, which enables us to consistently capture the
evolution of the superconducting phases throughout the entire $H$-$T$-$P$ phase space.
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Materials Science
The Roadmap of Inorganic Computational Materials Databases: Capabilities, Credibility, Coverage, and the Open Frontier
Miao Liu, Jianghao Jin, Tenglong Lu et al. (+4 more)
Computational materials databases have become central infrastructure for data-driven discovery of inorganic materials, yet their growth remains strikingly uneven across property families. This perspective synthesizes a systematic survey of mainstream density functional theory (DFT) software, the computational cost and credibility of nineteen material-property families, and the coverage of existing computational databases, into a coherent picture of where the field stands and where it should go. We show that the ecosystem of first-principles codes is methodologically mature: for nearly every property of technological interest, at least one production-grade code can compute it.The binding constraint is no longer methodological capability but the economics of trust - which properties can be computed cheaply enough, and accurately enough, to be harvested at database scale. Mapping database coverage onto a Gartner-style readiness cycle reveals a sharp divide: ground-state structure, energetics, elasticity, and
topology have reached routine production, while nine property families - including NMR/EPR parameters, core-level spectra, electron-
phonon properties, thermal conductivity, and
quantum transport - remain without any systematic computational database. We argue that these blank zones define the scientific opportunity of the next decade, and we propose a three-horizon roadmap: consolidating coverage and interoperability in the near term, industrializing mid-cost properties through surrogate-accelerated workflows in the medium term, and conquering the high-cost frontier through machine-learned interatomic potentials, autonomous computing infrastructure, and community governance in the long term.
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All authors Miao Liu, Jianghao Jin, Tenglong Lu, Jianguo Si, Yin Shi, Sheng Meng, Weihua Wang
Soft Condensed Matter
Spontaneous filament formation and network self-assembly via active phase separation
Elena Lucas, Varun Venkatesh and Amin Doostmohammadi
We introduce Active Model H$^{-}$, a scalar phase-field model of non-
equilibrium phase separation in the overdamped hydrodynamic limit, and show that it produces filamentous networks with enhanced connections and arrested coarsening, a morphology not observed in existing scalar active field theories. Isolated filaments are unstable to spontaneous bending, and the resulting
curvature drives self-propulsion towards the convex side, causing them to collide and assemble into a percolating network. The networks are locally non-
equilibrium, with anomalously curved edges, disordered vertex angles and heterogeneous topological charge, yet recover Lewis's law macroscopically. Under noise they show balanced break and reform dynamics.
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Strongly Correlated Electrons
Pressure induced structural phase transition and magneto-elastic coupling in Eu doped LaCrO$_3$
Asish Kumar Mishra, Mrinmay Sahu, Bhagyashri Giri et al. (+8 more)
In this study, we have carried out a detailed high pressure investigation on 5$\%$ Eu doped LaCrO$_3$ (ELCO) using synchrotron X-ray diffraction (XRD), micro Raman spectroscopy, and low-temperature magnetization measurements to correlate the structural and
magnetic properties under pressure. The high pressure XRD reveals the orthorhombic to rhombohedral structural phase transition around 10.6 GPa. The high pressure Raman data corroborate this result and indicate that the
lattice instabilities associated with the low-frequency soft modes play a crucial role in driving this transition. In addition, a pronounced anomaly in the Raman shift and integrated intensity of several Raman modes is observed around 4.5 GPa. By combining the low-temperature magnetization measurements with the anomalies observed in the XRD and Raman data and by comparing with the similar results in LaCrO$_3$ (LCO), a pressure-induced change in the
magnetic ground state to antiferromagnetic ordering is predicted.
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All authors Asish Kumar Mishra, Mrinmay Sahu, Bhagyashri Giri, Bidisha Mukherjee, Suvashree Mukherjee, Harekrishna Bhunia, Tamalkanti Mukherjee, Sujoy Ghosh, Partha Mitra, Peter Liermann, Goutam Dev Mukherjee
Superconductivity
Vortex-mediated spin current injection into two-dimensional superconductor NbSe2
Meng Yang, Xiaolong Yin, Jingjing Liu et al. (+7 more)
Injection of pure
spin current into
superconductors remains a major challenge in superconducting spintronics. Previous studies have primarily focused on
spin-polarized quasiparticles and
spin-triplet supercurrents, while
vortices, ubiquitous topological defects in type-2
superconductors, have been theoretically proposed as alternative carriers of
spin angular momentum, yet direct experimental evidence is still lacking. Here, we report the
vortex-mediated
spin current injection in NbSe2/LiAl2Fe3O8(LAFO) bilayer, an Ising
superconductor/ferrimagnetic
insulator heterostructure. Under an out-of-plane temperature gradient and an in-plane
magnetic field, the NbSe2/LAFO bilayer shows a pronounced thermoelectric peak near the upper critical
magnetic field, which has the opposite sign to the conventional
vortex Nernst signal observed in a single-layer NbSe2. The sign reversal suggests that the
vortex flow induced by
spin current injection is opposite to the flow driven by the temperature gradient, which is consistent with theoretical mechanisms including
spin-vorticity transmutation and the inverse
vortex spin Hall effect. By mapping the field temperature phase diagram, we reveal that the
spin current injection occurs exclusively in the
vortex liquid phase of NbSe2. Absence of the thermoelectric signal above the superconducting transition temperature further rules out the quasiparticle contribution. Our results establish
vortices as efficient carriers of
spin information in
superconductors, opening a new route towards
vortex-mediated superconducting spintronic devices.
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All authors Meng Yang, Xiaolong Yin, Jingjing Liu, Yifeng Chen, Qinwu Gao, Hongxing Zhu, Danni Huang, Lang Chen, Shuo-Ying Yang, Junxue Li
Materials Science · Cross-listed from physics.optics
Voltage-Current-Emission Framework of Time-Resolved Electroluminescence
Hui Bao, Longjia Wu, Yanan Guo et al. (+3 more)
Time-resolved electroluminescence has been a central methodology in the development of LED devices. However, it still lacks quantitative theoretical descriptions of time-resolved electroluminescence. By combining the equivalent
circuit models of
semiconductor devices and the carrier dynamics of electroluminescence processes, we here developed a Voltage-Current-Emission framework to illustrate time-resolved electroluminescence from the pulse voltage as input, to injection current and finally generate electroluminescence as output. The features of different LED devices can be quantitatively interpreted, confirming the universal applicability across LEDs with different materials and device structures. Importantly, the curves of time-resolved electroluminescence can be simulated to quantitatively describe the dynamics of current and carriers of LED operation. In all, the Voltage-Current-Emission framework offers theoretical guidance for achieving advanced LED devices for AI technology.
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All authors Hui Bao, Longjia Wu, Yanan Guo, Jianchang Yan, Ying Wang, Haizheng Zhong
Mesoscale and Nanoscale Physics
Observation of Dyakonov-Perel-type magnon spin relaxation in uniaxial antiferromagnetic insulators
Qinwu Gao, Andi Cong, Bokai Liang et al. (+6 more)
Long-distance transport of
magnon spin currents in antiferromagnetic (AFM)
insulators has attracted tremendous
attention recently, however, the AFM
magnon spin relaxation mechanisms remain elusive. Here, we report that the Dyakonov-Perel-type
magnon spin relaxation mechanism governs the
spin current transport along the easy axis in two prototypical uniaxial AFM
insulators, Cr2O3 and alpha-Fe2O3. First, an over 450% enhancement of the first-harmonic nonlocal signal induced by a
magnetic field is observed prior to the
spin-flop transition, which can be well-interpreted by our model incorporating Dyakonov-Perel-type
magnon spin relaxation. Secondly, we find that the
magnon spin diffusion length in both
crystals increases with
magnetic field and saturates at fields above 0.8 T, consistent with our model. Finally, the temperature dependence of the zero-field
magnon spin diffusion length in both AFM
insulators can be qualitatively explained through our model. These findings are valuable for the development of low-dissipation antiferromagnetic spintronic devices.
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All authors Qinwu Gao, Andi Cong, Bokai Liang, Meng Yang, Jingjing Liu, Lang Chen, Shiwei Wu, Ka Shen, Junxue Li
Superconductivity
Superconductivity at the metal-insulator phase boundary in a bulk nickelate at ambient pressure
Hyo-Bin Ahn, Xinglong Chen, Hong Zheng et al. (+9 more)
The discovery of superconductivity in nickelates has seeded a new field for exploring unconventional superconductivity in transition metal oxides. However, to date superconductivity has only been realized in thin films or under extreme pressure in the bulk. Here we report signatures of superconductivity at ambient pressure in bulk nickelate single
crystals of (La1-xPrx)4Ni3O8 and (La1-xYx)4Ni3O8, whose
crystal structure comprises interleaving trilayers of square-planar nickel oxide and fluorite-like spacer layers. The parent compound La4Ni3O8 exhibits an insulating ground state, where electrons order into intertwined, insulating charge/
spin stripes. Substitution of smaller lanthanide ions disrupts this order, eventually leading to a metallic ground-state. We find that superconductivity emerges in a narrow window proximate to the
insulator-metal phase boundary, where both metallic and charge-stripe phases co-exist. The observed low volume-fraction superconductivity is non-percolative, suggesting the prospect of filamentary superconductivity nucleated at the boundary between these phases. However, intergrowth defects that approximate the known infinite layer nickelates are observed in TEM, leaving open the possibility that superconductivity resides here rather than in the trilayer
matrix. Remarkably, the electronic phase diagrams of both the Y and Pr series coincide when parameterized by the volume of the fluorite like spacer layers, revealing that this steric parameter profoundly modifies the nickel oxide trilayer electronic structure. Our results identify better understanding of the co-existence region between metallic and charge-ordered phases as a priority for expanding the range of bulk, ambient-pressure nickelate superconductivity and establish spacer-layer engineering as a design tool for exploring this regime of phase competition.
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All authors Hyo-Bin Ahn, Xinglong Chen, Hong Zheng, Yu Zhang, Ramakanta Chapai, Yu Li, Arashdeep S. Thind, Robert F. Klie, Michael R. Norman, Ulrich Welp, J. F. Mitchell, Daniel Phelan
Superconductivity
Crystallographic imperfections and exotic superconductivity of UBe$_{13}$
Andreas Leithe-Jasper, Markus König, Yusei Shimizu et al. (+16 more)
The
symmetry of the superconducting gap is related to the
symmetry of the
crystal structure. In unconventional
superconductors, big changes of the critical temperature, critical field or even the gap structure can happen even for small perturbations of the
lattice. In this letter, we use microstructuring to study aluminium-free
crystals of UBe$_{13}$ which are expected to be closer to "perfect" material than previously studied aluminium-grown single
crystals. We compare the effect of minuscule imperfections on the value of the critical temperature and critical field, which, in the case of UBe$_{13}$, has drastic effects, supporting its unconventional nature. We
conjecture that this likely arises from the oxidation state of uranium, which is sensitive to its
crystal environment. Our findings suggests that uranium-based materials provide not only an excellent reservoir of new unconventional phenomena, but also a way to identify the gap
symmetry of unconventional
superconductors.
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All authors Andreas Leithe-Jasper, Markus König, Yusei Shimizu, Konstantin Semeniuk, Primož Koželj, Mitja Krnel, Paul Simon, Wilder Carrillo-Cabrera, Nazar Zaremba, Marcel Naumann, Ulrich Burkhardt, Thomas Doert, Yurii Prots, Alfred Amon, Elena Gati, Matthias Vojta, Yuri Grin, Elena Hassinger, Eteri Svanidze
Soft Condensed Matter
Sensitivity of Nucleation Thermodynamics and Kinetics to the Treatment of Long-Range Interactions
Fernanda Sulantay Vargas, Kimia Sinaeian and Amir Haji-Akbari
Nucleation rates are exponentially sensitive to the thermodynamic driving force and can therefore depend strongly on the treatment of long-range intermolecular interactions. Here, using the Lennard–Jones (LJ) system as a
benchmark, we combine molecular dynamics (MD) simulations, jumpy forward-flux sampling (jFFS), and free-energy calculations to quantify the effect of potential truncation on melting thermodynamics, homogeneous
crystal nucleation kinetics, and computational cost. Within the cutoff-radius range $2.5\sigma\le r_c\le 6\sigma$, the melting temperature at zero pressure varies by approximately 11%, while the nucleation rate changes by approximately ten orders of magnitude. By invoking classical nucleation theory (CNT), we show that this pronounced kinetic sensitivity originates primarily from cutoff-induced changes in the chemical potential difference between the
liquid and crystalline phases. Building on this observation, we develop a CNT-based framework for extrapolating finite-cutoff rates to the full-potential limit and for estimating the expected rate deviations at other cutoff radii and temperatures. These findings also provide a systematic basis for cutoff selection: the optimal cutoff should minimize computational cost while keeping the deviation from the full-potential rate within acceptable bounds. At $kT/\epsilon=0.5$, $r_c=4\sigma$ provides a reasonable compromise according to these criteria. We further demonstrate that conventional homogeneous tail corrections do not offer a reliable alternative, as they cannot consistently account for the
liquid, crystalline, and interfacial environments present during nucleation. Our findings highlight the need to specify and validate the truncation scheme as an integral component of force-field development in simulations of nucleation and other interfacial phase transitions within inhomogeneous environments.
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