Materials Science
Effect of Exchange-Correlation Functionals on Schottky Barriers at Si/Metal Interfaces
Viviana Dovale-Farelo and Kamal Choudhary
Accurate prediction of Schottky barrier heights (SBHs) at metal-
semiconductor (M-SC) interfaces is essential for understanding and optimizing charge injection in electronic and optoelectronic devices. However, first-principles calculations of SBHs remain challenging due to the combined difficulties of
semiconductor bandgap underestimation, metal
Fermi level placement,
lattice-mismatch, relative
geometric alignment and electrostatic potential
alignment across heterogeneous interfaces. In this work, we present a systematic and physically grounded assessment of computational strategies for SBH prediction using Si(111)/Metal (Al, Cu, Ag, Au) interfaces as representative test cases. We evaluate multiple exchange-correlation (XC) treatments, in combination with three distinct bulk reference protocols: relaxed bulk, relaxed bulk with
spin-orbit coupling, and strained bulk references consistent with the interface geometry. By benchmarking against experimental data, we demonstrate that structural and electrostatic consistency between interface and bulk reference calculations is the dominant factor governing SBH accuracy. We show that mixed hybrid-semilocal approaches combined with strained reference protocols yield uniformly positive and significantly improved SBHs, achieving near-experimental accuracy while maintaining a favorable balance between computational cost and predictive performance. Our results establish a clear and transferable methodology for reliable Schottky barrier prediction and provide practical guidance for large-scale screening and interface engineering.
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Materials Science · Cross-listed from cs.LG
A recipe for scalable attention-based MLIPs: unlocking long-range accuracy with all-to-all node attention
Eric Qu, Brandon M. Wood, Aditi S. Krishnapriyan et al. (+1 more)
Machine-learning interatomic potentials (MLIPs) have advanced rapidly, with many top models relying on strong physics-based inductive biases. However, as models scale to larger systems like biomolecules and electrolytes, they struggle to accurately capture long-range (LR) interactions, leading current approaches to rely on explicit physics-based terms or components. In this work, we propose AllScAIP, a straightforward,
attention-based, and energy-conserving MLIP model that scales to O(100 million) training samples. It addresses the long-range challenge using an all-to-all node
attention component that is data-driven. Extensive ablations reveal that in low-data/small-model regimes, inductive biases improve sample efficiency. However, as data and model size scale, these benefits diminish or even reverse, while all-to-all
attention remains critical for capturing LR interactions. Our model achieves state-of-the-art energy/force accuracy on molecular systems, as well as a number of physics-based evaluations (OMol25), while being competitive on materials (OMat24) and catalysts (OC20). Furthermore, it enables stable, long-timescale MD simulations that accurately recover experimental observables, including density and heat of vaporization predictions.
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All authors Eric Qu, Brandon M. Wood, Aditi S. Krishnapriyan, Zachary W. Ulissi
Superconductivity
Unifying description of competing chiral and nematic superconducting states in twisted bilayer graphene
Lucas Baldo, Patric Holmvall and Annica M. Black-Schaffer
We reveal a striking correspondence between electron- and
phonon-driven pairing in twisted
bilayer graphene (TBG) by mapping an atomistic electronically driven pairing model onto an effective inter-valley, intra-Chern description, originally proposed for
phonon-mediated superconductivity. Within the unified framework of intra-Chern pairing, we then analyze the competition between nematic and
chiral $d$-wave superconducting states. The latter corresponds to the extreme Chern-polarized limit and hosts unpaired flat bands within the superconducting gap, which generally disfavors it relative to the nematic states. Crucially, nematic order is locally preferred at each momentum, but the optimal nematic directions are incompatible across the Brillouin zone due to the broken rotation
symmetry. This momentum-space frustration still enables a
chiral ground state at large fillings or weak interactions in a symmetric parent state. Including heterostrain or inter-valley coherence further stabilizes the nematic ground state and sets the nematic direction. Under heterostrain, this direction shows a double winding with the strain axis, revealing the $d$-wave nature of the pairing, while inter-valley coherence makes it filling dependent. Our results thereby provide a unified understanding of superconductivity in TBG, in which electron- and
phonon-mediated pairing cooperate, and clarify the microscopic origin of the competition between the
chiral and nematic superconducting states.
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Mesoscale and Nanoscale Physics
Nanoscale Electronic Phase Separation Driven by Fe-site Ordering in Fe\textsubscript{5-x}GeTe\textsubscript{2}
Shreyashi Sinha, Ayan Jana, Suchanda Mondal et al. (+3 more)
Understanding how local structural order governs electronic correlations is essential for revealing the microscopic mechanism underlying emergent behavior in two-dimensional magnets. In the layered van der Waals ferromagnet Fe\textsubscript{5-x}GeTe\textsubscript{2}, intrinsic Fe-site disorder provides a natural platform to probe this interplay. Here, we establish a direct atomic scale correlation between Fe-site ordering and local electronic structure by combining high-resolution scanning tunneling microscopy with density functional theory calculations. Scanning tunneling microscopy resolves two coexisting surface phases, a $\sqrt{3} \times \sqrt{3}$ superstructure associated with ordered Fe(1) configurations and an undistorted $1 \times 1$ hexagonal Te
lattice in Fe(1)-deficient regions. Spatially resolved spectroscopy shows that the $\sqrt{3}$-ordered domains exhibit metallic behavior, whereas Fe(1) vacant areas display a suppressed density of states(DOS) near the
Fermi level, indicative of pseudogapped electronic states. The nanoscale coexistence of these distinct electronic responses provides direct evidence of electronic phase separation driven by Fe-site ordering. First-principles calculations reveal that
symmetry allowed hybridization between Fe 3d and Te 5p orbitals reconstructs the low-energy electronic structure, giving rise to the contrasting tunneling signatures of ordered and disordered phases. Bias-dependent local DOS simulations reproduce the experimentally observed contrast
evolution and reveal that hybridization induced out of plane orbital character governs the spatial modulation of tunneling conductance. These results provide a microscopic framework linking atomic-scale structural order to nanoscale electronic inhomogeneity in van der Waals magnets.
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All authors Shreyashi Sinha, Ayan Jana, Suchanda Mondal, Ravi Prakash Singh, Manoranjan Kumar, Sujit Manna
Materials Science
Deterministic Electrical Switching in Altermagnets via Surface Antisymmetry Groups
K. D. Belashchenko
A surface antisymmetry group framework is developed to establish design rules for deterministic electrical switching of the Néel vector in a film of a collinear bipartite antiferromagnet. In centrosymmetric altermagnets, where linear current-induced
spin-orbit torques vanish in the bulk, staggered effective fields can nevertheless exist as a macroscopic interfacial response, whose allowed tensor form is determined by the surface antisymmetry point group for the given surface orientation. Such effective fields do not require sublattice equivalence to be broken by the surface and can arise via the Edelstein mechanism driven by sublattice-odd interfacial
spin-orbit coupling. General
symmetry obstructions to bipolar switching that are valid to all orders in torque angular harmonics are also derived. Separately, the structure of the
spin conductivity tensor determines which surface orientations allow transverse
spin current generation via the nonrelativistic
spin-splitter effect. Taken together, these
symmetry-enforced properties establish which surface orientations of $d$-wave altermagnets can serve as deterministically switchable
spin current sources in
spin-torque
heterostructures. Because the design rules are based solely on the surface antisymmetry point group, the
symmetry-allowed staggered effective fields are robust against averaging over
equilibrium surface roughness.
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Superconductivity · Cross-listed from quant-ph
Towards Studying Superconductivity in the Fermi-Hubbard Model on Rydberg Atoms
Kübra Yeter-Aydeniz and Nora M. Bauer
We present a method for calculating the ground state energy of the
Fermi-Hubbard model leveraging Rydberg atom processors and sample-based
quantum diagonalization (SQD). By exploiting the perturbative relationship between the
Fermi-Hubbard and Heisenberg models, the procedure samples from the Heisenberg model as prepared on the Rydberg atom processor, and uses the samples to diagonalize the
Fermi-Hubbard model for large U. We include anisotropy and next-nearest-neighbor interactions and discuss the relevant regime for quasi-superconductivity in the 1-dimensional
Fermi- Hubbard model. Numerical and experimental results on the Aquila
quantum processor are presented for ground state energy calculations as well as the chemical potential. We find that the Heisenberg model sampling in the studied regime is sufficient to converge near to the ground state for up to 56
qubits, and we see a clear advantage of Rydberg atom sampling as opposed to random sampling even with 10x more samples for diagonalization. We also present a gate-based implementation of the gate-based SQD
algorithm on IBM
Quantum hardware for 56-
qubit Hubbard model as a
benchmark. Finally, we provide a gap analysis for studying emergent superconductivity using this method.
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Strongly Correlated Electrons
Tomographic collective modes in a magnetic field
Jeff Maki and Johannes Hofmann
Two-dimensional
Fermi liquids at low temperatures have been theoretically established to exhibit an odd-even effect in the collective quasiparticle relaxation rates where even-parity deformations of the
Fermi surface decay at a much faster rate than odd-parity ones. A predicted consequence of this effect is a new tomographic transport regime that mixes hydrodynamic and collisionless transport. In the presence of a
magnetic field, however, the tomographic regime is expected to evolve towards conventional transport regimes as soon as the cyclotron radius becomes smaller than the dominant odd-parity mean-free path. In this work, we examine this transition from the point of view of collective modes, using a numerically exact solution of the linearized Boltzmann equation within a generalized relaxation time approximation for the odd-parity and even-parity modes. In the absence of a
magnetic field, the transverse conductivity exhibits two diffusive tomographic collective modes, and we find that at a critical
magnetic field one of these two tomographic modes disappears. Which tomographic mode persists depends on the Landau parameters, and becomes increasingly dominated by hydrodynamic modes at high fields. We corroborate our analysis using a variational approach for the
Fermi surface deformation that captures the angular structure of the deformation and the critical
magnetic field strength. The collective modes discussed here can in principle be observed by examining the damping of longitudinal and transverse current responses in finite
magnetic fields.
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Materials Science
Epitaxial stabilization of magnetic GdAuSb/LaAuSb superlattices
Patrick J. Strohbeen, Soohyun Im, Tamalika Samanta et al. (+7 more)
We report the epitaxial stabilization of GdAuSb films and GdAuSb/LaAuSb superlattices via molecular beam epitaxy on (0001)-oriented Al$_{2}$O$_{3}$ substrates. GdAuSb crystallize in the Au-Au dimerized YPtAs structure type (space group $P6_{3}/mmc$), the same structure as the Dirac semimetal LaAuSb. Angle-resolved photoemission spectroscopy (ARPES) measurements show similar near $E_F$ bandstructures for GdAuSb and LaAuSb, plus a rigid band shift for GdAuSb towards more hole-like behavior and core-like Gd $4f$ states $\sim 9$~eV below the
Fermi energy. LaAuSb/GdAuSb superlattices exhibit sharp superlattice fringes by X-ray diffraction and atomically-precise interfaces by scanning transmission electron microscopy. Superlattices display two transitions in temperature-dependent resistvity, compared to a single Néel temperature for thick GdAuSb films. Superlattices of $Ln$AuSb materials ($Ln=$ rare earth) with atomically abrupt interfaces offer a new epitaxial platform for control of
magnetic and topological order via tunable intralayer exchange and reduced dimensionality.
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All authors Patrick J. Strohbeen, Soohyun Im, Tamalika Samanta, Zachary LaDuca, Dongxue Du, Estiaque H. Shourov, Jessica L. McChesney, Fanny Rodolakis, Paul M. Voyles, Jason K. Kawasaki
Mesoscale and Nanoscale Physics · Cross-listed from quant-ph
Methods for characterization of atomic-scale field emission point-electron-source
Shuai Tang, Mingkai Gou, Yingzhou Hu et al. (+7 more)
Field emission (FE) electron sources are made close to atomic-scale to reach the highest spatial resolution as well as stable emission for electron microscopy, electron beam inspection and lithography. At present, no single agreed method exists of using FE current-voltage data to extract the apparent emission area, which is needed for predicting some beam properties. The 1956 theory of Murphy and Good (MG) is better physics than the 1920s theory of Fowler and Nordheim (FN) and colleagues, but many researchers use simplified FN theory to analyse experimental data. The present paper reports an experimental method of finding apparent emission area, based on using field ion and field electron microscopes (FIM-FEM). The discrepancy of emission area between the FIM-FEM method and MG-based analysis is a factor of 7.4, while that with simplified FN-based analysis is about 25, confirming MG theory is better for FE data analysis. The result allows deduction of key indicators, including source energy spread, reduced brightness and emission efficiency. A downloadable program is made available to help analysis. Our work provides a new experimental method of characterizing FE electron sources, especially the atomic-scale cold cathode, for which existing plot-based data-analysis methods are not suitable.
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All authors Shuai Tang, Mingkai Gou, Yingzhou Hu, Jie Tang, Yan Shen, Yu Zhang, Lu-Chang Qin, Ningsheng Xu, Richard G. Forbes, Shaozhi Deng
Mesoscale and Nanoscale Physics
Altermagnets Enable Gate-Switchable Helical and Chiral Topological Transport with Spin-Valley-Momentum-Locked Dual Protection
Xianzhang Chen, Jiayong Zhang, Bowen Hao et al. (+5 more)
We establish a unified,
symmetry-driven framework that combines the alternating
spin splitting of altermagnets with valley
topology to realize and electrically interconvert helical and
chiral topological phases within a single material platform. We first demonstrate a
magnetic analogue of the
quantum spin Hall effect in altermagnets, hosting helical
spin-valley-momentum-locked (SVML) edge states characterized by a composite
spin-valley Chern number Csv = 2. Large-scale
quantum transport simulations show these SVML edge states exhibit fully quantized
spin conductance robust against nonmagnetic and long-range
magnetic disorder, reflecting their dual topological protection, while remaining vulnerable to short-range
magnetic disorder. Exploiting that the counterpropagating SVML modes are linked by
crystal rotation
symmetry, we introduce a gate-tunable sublattice-staggered potential that selectively gaps one valley and converts the helical state into a
chiral quantum anomalous
Hall phase with Csv = 1, robust against all disorder types. Reversing the potential switches the transmitted
spin-valley polarization. Our first-principles calculations identify monolayer V2STeO and VO families as realistic platforms supporting both helical and
chiral topological phases and their electrical switching. These results establish altermagnets as electrically programmable platforms for robust topological devices across charge,
spin, and valley.
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All authors Xianzhang Chen, Jiayong Zhang, Bowen Hao, Jiahui Qian, Ziye Zhu, Igor Zutic, Zhenyu Zhang, Tong Zhou
Mesoscale and Nanoscale Physics
Linearly Polarized Light-Induced Anomalous Hall Effect and Topological Phase Transitions in an Altermagnetic Topological Insulator
Yichen Liu, Tongshuai Zhu and Haijun Zhang
A recently identified class of collinear
magnetic order, characterized by vanishing net magnetization yet unconventional
spin splitting, known as altermagnets (AMs), has attracted significant research interest. Controlling the unconventional
spin splitting and the associated band
topology in AMs offers opportunities for realizing novel
spin and topological transport phenomena. In this work, using Floquet engineering with periodically driven linearly polarized light (LPL), we explore light-induced control of an AM topological
insulator. Remarkably, we find that AMs and conventional antiferromagnets (AFMs) exhibit distinct responses under LPL irradiation. Specifically, since LPL breaks neither time-reversal ($\mathcal{T}$)
symmetry nor parity-time-reversal ($\mathcal{PT}$)
symmetry, it is incapable of generating
spin splitting or inducing an anomalous
Hall effect (AHE) in conventional AFMs. In contrast, AMs intrinsically lack both $\mathcal{T}$ and $\mathcal{PT}$
symmetries. Their
spin-up and
spin-down bands are related by the combined
symmetry of time reversal $\mathcal{T}$ and a
crystal rotation. We show that LPL readily breaks these
symmetries, thereby triggering a finite AHE exclusively in AMs. Furthermore, LPL can drive the AM topological
insulator into a fully
spin-polarized Chern insulating phase. Our findings not only provide a robust experimental scheme to distinguish AMs from conventional AFMs, but also establish a promising pathway toward dissipationless spintronic applications.
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Materials Science
Structural Commonalities in Amorphous Elemental Materials
I. Rodríguez, R. M. Valladares, A. Valladares et al. (+5 more)
In the In recent times, the research community has explored diverse structures and novel fabrication methods for amorphous solids. This work investigates structural trends among different classes of amorphous materials to identify universal commonalities and fundamental differences. It is found that amorphous
semiconductors exhibit similar Pair Distribution Functions (PDFs), characteristic of their underlying network-forming nature. On the other hand, amorphous metallic systems also display internally consistent PDF profiles, but different from those of the semiconducting materials. A comparative analysis of short-range and medium-range order reveals that while
semiconductor structures feature a well-isolated first peak, with a zero-intensity region between the first and second peaks, metallic systems maintain a significant non-zero value between the first and second peaks. Furthermore, the second peak in metallic systems is bimodal, featuring a distinct elephant-like profile. Amorphous semi-metals display a still different profile, and the PDFs for Bi, for example, are similar to those for As and Sb. To deepen this structural comparison, we have incorporated amorphous Plane Angle Distributions (PADs), providing a more complete perspective on the local geometry. We introduce a renormalization approach that uses the positions of the first peaks in the PDFs to quantify these structural coincidences and discuss the implications.
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All authors I. Rodríguez, R. M. Valladares, A. Valladares, D. Hinojosa-Romero, F. B. Quiroga, S. Calderón-Alba, R. S. Vilchis-Peyret, A. A. Valladares
Strongly Correlated Electrons
Parity readout in Majorana box qubits from the dispersive to the resonant regime
Sara M. Benjadi and Reinhold Egger
We study theoretical models for charge reflectometry and capacitive readout of the Majorana parity degree of freedom in Majorana box
qubits, taking into account decoherence channels within the framework of the Lindblad master equation. Noting that a parity-dependent dynamical susceptibility $\chi_z(\omega)$ governs both readout schemes, we provide a general expression for $\chi_z(\omega)$ which covers the full crossover from the resonant regime to the off-resonant dispersive regime. In addition, we re-examine previous results which were obtained under a semiclassical factorization assumption. Using three different error measures, we show that this approximation is quantitatively justified in the dispersive regime. In the resonant regime, however, we find deviations from exact reference data, obtained by numerical solution for the steady state of the full Lindblad equation. These deviations are typically of the order of a few percent in the considered error measures.
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Other Condensed Matter
Skyrmion Cyclotron Resonance in Ferrimagnets
Eugene M. Chudnovsky and Dmitry A. Garanin
We show that a resonance due to gyroscopic motion of skyrmions, conceptually similar to the electron cyclotron resonance in metals, can be excited in a ferrimagnetic film by a
spin current or microwaves. It must permit unambiguous measurement of the skyrmion mass for which a universal expression depending solely on the exchange interaction between
spins belonging to two different ferrimagnetic sublattices is derived. The dependence of the skyrmion cyclotron frequency on parameters is computed for a TM/RE ferrimagnet, using CoGd as an example. The cyclotron frequency exhibits a dip near the angular momentum compensation point, where it hybridizes with the
ferromagnetic resonance. The skyrmion cyclotron mode is studied for individual skyrmions and for skyrmion
lattices, where the effect must be strong enough to be observed in microwave and
spin-current experiments.
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Other Condensed Matter
Density of States Weighted Decoherence Probe Formalism for Charge Transport in DNA
Hashem Mohammad and M.P. Anantram
Nanoscale molecular systems such as DNA require an atomistic
quantum treatment to accurately capture their electrical properties, owing to their small dimensions. A central challenge in modeling transport through these systems is the inclusion of phase-breaking scattering. Decoherence-probe methods enable such modeling for large systems, but existing implementations have limitations. Energy-independent scattering rates tend to overly broaden energy levels, yielding an unphysically large density of states (DOS) within energy gaps. Conversely, energy-dependent models may introduce spurious energy levels and transmission peaks and require additional fitting parameters. To address these issues, we use a DOSweighted decoherence model in which the scattering rate and equivalently, the associated decoherence probe self-energy is proportional to the local DOS. The model iteratively updates the decoherence selfenergy and the DOS until self-consistency is achieved. This approach yields energy and spatially dependent scattering rates that avoid spurious energy levels without the excessive broadening of DOS in energy gaps. We also examine the impact of partitioning schemes that prevent artificial pathways for charge transport and discuss how they can be avoided. Overall, the DOS-weighted model provides an improved and more physically grounded framework for simulating charge transport in DNA and potentially other weakly coupled molecular systems.
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Materials Science
Revisiting the symmetry and optical phonons of altermagnetic $\alpha$-MnTe
Ece Uykur, Marcos V. Gonçalves-Faria, Sahana Rößler et al. (+5 more)
Using infrared (IR) and Raman spectroscopies combined with high-resolution x-ray diffraction, we address several controversial aspects of altermagnetic $\alpha$-MnTe. We show that mechanical stress applied to
crystals of this material causes a drastic broadening of Bragg peaks that conceals signatures of additional phases present in the sample. Indeed, spatially resolved Raman spectroscopy reveals that the modes around 175 cm$^{-1}$ often reported in $\alpha$-MnTe are not reproducible across different positions and samples and originate from the secondary phase of MnTe$_2$. By combining spectroscopic probes with ab initio calculations, we establish the IR-active optical
phonon of $\alpha$-MnTe around 155 cm$^{-1}$ ($E_{1u}$) and the Raman-active optical
phonon around 100 cm$^{-1}$ ($E_{2g}$) at room temperature. Two intense Raman modes around 120 and 140 cm$^{-1}$ are shown to be intrinsic, even though they can not be assigned to $\Gamma$-point optical
phonons. These modes couple to
magnetic order in $\alpha$-MnTe and also to the transient reflectivity resulting in coherent oscillations. Both 6-fold rotation
symmetry and inversion
symmetry are preserved in $\alpha$-MnTe within our experimental resolution.
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All authors Ece Uykur, Marcos V. Gonçalves-Faria, Sahana Rößler, Victoria A. Ginga, Marcus Schmidt, Stephan Winnerl, Manfred Helm, Alexander A. Tsirlin
Strongly Correlated Electrons
AKLT Hamiltonian from Hubbard tripods
Claire Benjamin, Dániel Varjas, Gábor Széchenyi et al. (+2 more)
We investigate how the
spin-1 Affleck-Kennedy-Lieb-Tasaki (AKLT)
Hamiltonian can emerge from a microscopic fermionic model based on half-filled Hubbard tripods. We first show that a single tripod hosts a robust threefold-degenerate low-energy
manifold corresponding to an effective $S = 1$ degree of freedom. This
manifold prevails over a broad range of interactions and remains stable against moderate disorder. We then combine exact diagonalization with fourth-order quasi-degenerate perturbation theory to derive an effective bilinear-biquadratic
spin model for a pair of coupled tripods and identify coupling regimes where the target ratio is approached. In particular, tuning leg-center hopping together with two
symmetry-inequivalent leg-leg hoppings yields the characteristic singlet-triplet degeneracy associated with a biquadratic-to-bilinear ratio close to 1/3. Extending the analysis to three tripods, we compare nonequivalent coupling geometries and find a strategy that suppresses unwanted longer-range and multispin terms while preserving the target nearest-neighbor couplings in the weak-coupling regime. These results establish a concrete bottom-up route from Hubbard clusters to valence-bond-solid
spin physics in tunable
quantum-dot arrays.
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All authors Claire Benjamin, Dániel Varjas, Gábor Széchenyi, Judit Romhányi, László Oroszlány
Materials Science
Real-time exciton dynamics in two-dimensional materials under ultrashort laser pulses
Dmitry Tumakov and Daria Popova-Gorelova
The optical response of two-dimensional materials is often significantly impacted by excitonic effects due to the reduced screening of attractive Coulomb interactions in low-dimensional systems. Accurate modeling of
exciton formation and real-time dynamics is essential to understanding their ultrafast optical properties. In this study, we theoretically investigate the
exciton dynamics in a two-dimensional hexagonal boron nitride (h-BN) and a germanium sulfide (GeS) monolayers exposed to an ultrashort
laser pulse. We analyze the system's response to the external field in one- and two-
photon excitation regimes. For our calculations, we combine a state-of-the-art ab initio approach to study
exciton dynamics with a highly precise numerical scheme. We incorporate electron-hole interactions through a non-local self-energy operator derived from the many-body perturbation theory (MBPT) within the time-dependent adiabatic $GW$ (TD-a$GW$) approximation. We implement this approach using the full-electron LAPW+lo method in the all-electron exciting package. Our results elucidate the role of many-body effects in shaping ultrafast excitonic processes in two-dimensional materials, contributing to the fundamental understanding necessary for optoelectronic and photonic applications.
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Soft Condensed Matter
Linear control theory for jammed particle systems
Erin G. Teich, Jason Z. Kim and Dani S. Bassett
Amorphous particulate matter constitutes a wide range of natural and synthetic materials. Despite this ubiquity, the way in which these systems' disordered microstructure couples to their often subtle and complex dynamical behavior is not yet fully understood, with profound consequences for phenomena ranging from landscape
evolution to cellular unjamming during tumor metastasis. With this paper, we introduce tools from linear control theory that quantify system response to external input, and demonstrate their utility in elucidating the dynamics of jammed amorphous materials under stress. Our results indicate that average controllability, the response of a system to perturbation, strongly correlates with particle rearrangement in systems subject to quasistatic shear, implying that average controllability is an accurate predictor of rearrangement dynamics in certain contexts. Moreover, we show that the time scale over which average controllability is calculated can be tuned to optimize its predictive capacity for particle rearrangement. Values of the optimal time scale provide physical insight into the system; namely, that multiple rearranging particles participate on average in vibrational eigenmodes of lower and lower energy as the system is sheared until the rearrangement event. Broadly, our study demonstrates that linear control theory is a promising mathematical framework for predicting and designing mechanical response in disordered media.
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Materials Science
Giant orbital magnetoresistance in the antiferromagnet CoO driven by dynamic orbital angular momentum interaction
Christin Schmitt, Sachin Krishnia, Edgar Galindez-Ruales et al. (+12 more)
Recent predictions of orders of magnitude larger orbital current effects compared to
spin currents have attracted significant interest. However, the full potential of
giant orbital currents remains to be fully harnessed, since so far, the orbital currents need to be converted into
spin currents before they can interact with the static magnetization that is dominated by
spin angular momentum in conventional magnets. By using a magnet dominated by orbital angular momentum, we demonstrate a more than fifty-fold enhancement in orbital
Hall magnetoresistance in CoO/Cu*, compared to conventional CoO/Pt. This is found to be driven by a unique interaction between dynamic orbital angular momentum from surface oxidized Cu* (i.e., the orbital current) and the static orbital angular momentum which constitutes the
magnetic moments in the
antiferromagnetic insulator CoO. A distinctive scattering mechanism for orbital currents at the CoO interface leads to a sign reversal in orbital magnetoresistance in CoO/Cu* compared to CoO/Pt. Our results show how by using orbital angular momentum-dominated materials such as CoO, we can harness the benefits of
giant orbital currents that have not been possible using conventional
spin-dominated magnets, for orbitronics-based devices, offering unprecedented energy efficiency for operations of antiferromagnets that combine ultimate stability with THz dynamics.
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All authors Christin Schmitt, Sachin Krishnia, Edgar Galindez-Ruales, Luca Micus, Takashi Kikkawa, Hiroki Arisawa, Marjana Lezaic, Duc Tran, Timo Kuschel, Jairo Sinova, Eiji Saitoh, Gerhard Jakob, Olena Gomonay, Yuriy Mokrousov, Mathias Kläui
Superconductivity
Exotic Pressure-Driven Band Gap Widening in Carbon Chain-Filled KFI Zeolite and Its Pathway to High-Pressure Semiconducting Electronics and High-Temperature Superconductivity
C.T.Wat, K.C.Lam, W.Y.Chan et al. (+6 more)
Semiconducting devices face persistent challenges in operating at high pressure, as the band theory predicts that materials transition to a more metallic state under compression. However, our findings with carbon chains in KFI substrates reveal a conditional deviation from this norm. We not only witness the transition from polyyne (
semiconductor) to cumulene (metal) at medium pressure, but we also observe an unexpected re-entrance of the polyyne at high pressures, where the band gap in the polyyne increases with pressure. In addition, the synthesis of long cumulene chains has posed a longstanding challenge in the quest for high-temperature organic superconductivity. We have identified critical conditions for synthesizing extended cumulene chains within zeolite frameworks, highlighting the interplay between unconventional charge density waves and significant torsions. The KFI zeolite facilitates the formation of carbon chains exceeding 5,000 atoms, in stark contrast to around 100 other zeolites that are limited to ~10 atoms. The cumulene@KFI system demonstrates a superconducting transition temperature reaching ~62 K, surpassing the highest reported values for bulk iron-based
superconductors. This interplay between carbon structures and superconductivity not only advances our understanding of charge density waves but also heralds a new era in the study of novel applications
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All authors C.T.Wat, K.C.Lam, W.Y.Chan, C.P.Chau, S.P.Ng, W.K.Loh, L.Y.F.Lam, X.Hu, C.H.Wong
Materials Science
Understanding the anisotropic response of $\beta$-Ga$_2$O$_3$ to ion implantation
Duarte Magalhães Esteves, Ru He, Sérgio Magalhães et al. (+8 more)
While $\beta$-Ga$_2$O$_3$ is considered a promising wide bandgap
semiconductor, the impact of ion-induced defect formation and anisotropic elasticity remains poorly understood. Here, we combine a simulation and experiment X-ray diffraction (XRD) study of the strain-stress dynamics induced by ion implantation into $\beta$-Ga$_2$O$_3$ single-
crystals with different surface orientations. The strain accumulation in the out-of-plane direction is observed by XRD to occur in an anisotropic manner, with compressive strain along the [010] direction and tensile strain along the directions perpendicular to (100) and (001). An anisotropic stress/strain accumulation model is proposed and probed via Molecular Dynamics (MD), showing an excellent agreement with the experiments. For higher damage levels, pole figures obtained both experimentally and by MD via a novel reciprocal-space projection method reveal an orientation-independent $\beta$-to-$\gamma$ phase transition, with a fixed crystallographic relationship between the polymorphs. By exploring the strain-stress dynamics in anisotropic systems, this work establishes a method to directly compare macroscale diffraction experiments and atomistic simulations and opens a new path to engineer the properties of such systems utilizing their anisotropic response to ion implantation/irradiation.
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All authors Duarte Magalhães Esteves, Ru He, Sérgio Magalhães, Miguel Carvalho Sequeira, Ângelo Rafael Granadeiro da Costa, Julia Zanoni, Joana Rodrigues, Teresa Monteiro, Flyura Djurabekova, Katharina Lorenz, Marco Peres
Materials Science
Unlocking extreme doping and strain in epitaxial monocrystalline silicon
Léonard Desvignes, Dominique Débarre, Ludovic Largeau et al. (+8 more)
Hyperdoping, overcoming the solubility limit of dopants in a crystalline
semiconductor, is a fertile method for the enhancement of the electrical, structural and optical devices' performances and for the exploration of exotic phases such as superconductivity. We demonstrate an unprecedented control on the dopant concentration and
lattice deformation via nanosecond
laser doping in epitaxial boron doped silicon, achieving record carrier concentrations (8 at.%) and
lattice deformations (3 %). Probing the microscopical hyperdoping limitations, we show that the relevant mechanisms are caught by a simple combinatorial model, which quantitatively explains both the experimental carrier concentration and
lattice deformation
evolution. First principle calculations complete and support such simple model. Indeed, at the high doping levels now attainable, the maximum carrier concentration is inherently limited by the probability of two or three substitutional dopants occupying neighboring
lattice sites, forming partially inactive complexes that we detail. This description is valid in the case of perfect layers with no crystallographic defects and a fully substitutional dopant occupation, highlighting the quality of the epitaxial layers realized.
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All authors Léonard Desvignes, Dominique Débarre, Ludovic Largeau, Géraldine Hallais, Gilles Patriarche, Giacomo Priante, Eric Ngo, Olivia Mauguin, Alberto Debernardi, Bernard Sermage, Francesca Chiodi
Superconductivity
Plasmon decay and non-equilibrium steady states in Josephson junction chains
Lucia Vigliotti, Andrew P. Higginbotham and Maksym Serbyn
Josephson junction (JJ) chains combine the coherence of superconductivity with the controllability of microwave-frequency
circuits, making them a powerful platform for
circuit quantum electrodynamics. In this work we consider a long JJ chain that effectively realizes a multi-mode cavity with nonlinear dispersion and additional multi-mode interactions. Individual modes appearing due to the finite size of the chain can be experimentally probed via microwave spectroscopy, both in
equilibrium and in driven far-from-
equilibrium settings. We study the role of multi-mode interactions in degrading internal coherence – observable as excess linewidth – in both
equilibrium and driven regimes. Focusing on two-into-two mode scattering as the leading relaxation process, we classify the relevant scattering processes and derive their expected temperature- and frequency-scaling under
equilibrium conditions. For experimentally relevant parameters, we show that the
equilibrium decay rate is dominated by non-resonant processes, however weakly driving a particular set of modes out of
equilibrium enhances resonant scattering, leading to observable signatures in the distribution function and linewidth. Finally, in the strong non-
equilibrium regime we report a crossover to a qualitatively different non-
equilibrium steady state.
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Disordered Systems and Neural Networks · Cross-listed from math.PR
One-sided large deviations for the ground-state energy of spin glasses
Hong-Bin Chen, Alice Guionnet, Justin Ko et al. (+2 more)
We describe the large deviations above its typical value of the maximal energy of a
spin glass with +/-1
spins. Thanks to the relatively explicit description of the rate function we identify, we then show that the latter is asymptotically quadratic near its minimum if and only if an external
magnetic field is present. The proof starts from a Parisi-type formula for the fractional moments of the partition function, which we then leverage to obtain the limit of the Laplace transform of the maximum energy. Using convex-duality arguments, we then rewrite this Laplace transform as a supremum over martingales, and thereby deduce the large-deviation principle with explicit rate function.
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All authors Hong-Bin Chen, Alice Guionnet, Justin Ko, Bertrand Lacroix-A-Chez-Toine, Jean-Christophe Mourrat
Mesoscale and Nanoscale Physics
Universal Dynamical Scaling of Strong-to-Weak Spontaneous Symmetry Breaking in Open Quantum Systems
Chang Shu, Kai Zhang, Zhu-Xi Luo et al. (+2 more)
Strong-to-weak spontaneous
symmetry breaking (SWSSB) defines a mixed-state phase of matter–without a pure-state counterpart–in which nonlinear observables such as the Rényi-2 correlator develop long-range order while conventional linear correlations remain short-ranged. Here we study the emergence of SWSSB in one-dimensional open
quantum systems governed by Lindbladian
evolution, where the transition time diverges with system size and SWSSB appears only asymptotically in the steady state. By tracking the late-time growth of the Rényi-2 correlation length, we uncover a universal dynamical regime controlled purely by the
symmetry class of the Lindbladian. Contrary to the conventional expectation that late-time dynamics are governed by the low-lying Liouvillian spectrum, we find that the time dependence of the SWSSB transition–exponential versus algebraic–is dictated solely by
symmetry, independent of details of the Lindbladian, including whether the Liouvillian spectrum is gapped or gapless. For $\mathbb{Z}_2$-symmetric dynamics, the Rényi-2 correlation length grows exponentially in time–even when the spectrum is gapless–yielding an effective transition time $t_c \propto \operatorname{ln} L$ and enabling rapid preparation of the $\mathbb{Z}_2$ SWSSB steady state. In contrast, U(1)-symmetric dynamics exhibit algebraic scaling, $t_c \propto L^{\alpha}$, with a filling-dependent dynamical exponent: ballistic growth ($\alpha \approx 1$) at finite filling crosses over to diffusive scaling ($\alpha = 2$) in the zero-filling limit. These results establish
symmetry–rather than spectral gap structure–as the controlling principle for SWSSB late-time dynamical scaling, and open a new route to nonequilibrium
symmetry breaking in open
quantum systems.
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All authors Chang Shu, Kai Zhang, Zhu-Xi Luo, Yizhi You, Kai Sun
Materials Science · Cross-listed from physics.comp-ph
Frustrated supermolecules: the high-pressure phases of crystalline methane
Marcin Kirsz, Miguel Martinez-Canales, Ayobami D. Daramola et al. (+3 more)
Methane is the simplest hydrocarbon, yet it exhibits an extraordinarily complicated series of
crystal phases. Notably, the non-plastic phases have large unit
cells with nearly, but not quite cubic
symmetry. Furthermore, although non-polar molecules interact very weakly, their reorganisation across phase transitions is very sluggish. Here, we demonstrate that these complex structures can be understood as simple packing of near-spherical supermolecular clusters of methane molecules: the departure from cubic
symmetry arising from the non-spherical nature of the molecules. We use molecular dynamics based on density functional theory calculations to simulate the finite-temperature
crystal structures of methane, finding that the complex Phase A is based around a 13-molecule regular icosahedron, with 8 additional molecules forming the 21-molecule unit
cell. Similarly, Phase B is based on a body-centred cubic bcc packing of 17-molecule Z16 polyhedra, with the remaining 12 molecules per
cell in tetrahedral interstices. We demonstrate that the favored intermolecular separation depends sensitively on molecular orientation, leading to hindered rotation and suppressed
entropy. The structures are determined by a trade-off between efficient packing and
entropy.
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All authors Marcin Kirsz, Miguel Martinez-Canales, Ayobami D. Daramola, John S. Loveday, Ciprian G. Pruteanu, Graeme J Ackland
Mesoscale and Nanoscale Physics · Cross-listed from quant-ph
Thermodynamics of Quantum Coupled Transport
Shuvadip Ghosh and Arnab Ghosh
This review presents a thermodynamic perspective on
quantum coupled transport processes in nanoscale systems. Our analysis is formulated within the framework of
entropy production rate, the central quantity governing non-
equilibrium processes and expressed through conjugate force-flux pairs. Although thermodynamic laws are universal across classical and
quantum domains, the discussion is developed within a microscopic open
quantum system framework, focusing on
quantum dots (QDs) coupled to electronic reservoirs. We first examine elementary single transport processes and highlight their strong thermodynamic constraints in the near-
equilibrium regime. This motivates the study of coupled transport, where multiple force-flux pairs coexist and interact, leading to richer thermodynamic behaviour. Using
entropy production as the guiding principle, we analyse coupled energy and particle transport in a minimal two-terminal single-QD setup and show how conventional thermoelectric phenomena, including Seebeck and Peltier effects as well as thermoelectric heat engines and refrigerators, naturally emerge as thermodynamic cross-effects. We then extend the framework to a three-terminal coupled
quantum dot (CQD) geometry, which provides a versatile platform for studying coupled transport and reduces, under suitable constraints, to the well-known Sánchez-Büttiker configuration. Beyond standard cross-effects, we discuss the phenomenon of inverse currents in coupled transport (ICC), where a current flows against mutually parallel thermodynamic forces without violating the second law. We show that ICC requires breaking the
symmetry between energy and particle transport and identify the conditions for its realization in coupled
quantum-dot systems with attractive interdot interactions.
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Superconductivity
Competition between Charge Density Wave and Superconductivity in a Janus MXene Mo2NF2
Jakkapat Seeyangnok, Udomsilp Pinsook and Graeme J Ackland
Charge-density-wave (CDW) order and superconductivity often compete in low-dimensional materials, yet their interplay in Janus MXenes remains largely unexplored. Here, we present a comprehensive first-principles investigation of the structural, vibrational, and electronic properties of Mo2NF2.
Phonon calculations reveal an unstable soft
phonon mode at the M point in the high-
symmetry structure, signaling a CDW instability. Analysis of
phonon linewidths and the real and imaginary parts of the bare electronic susceptibility demonstrates that the CDW is not driven by simple
Fermi-surface nesting but instead originates from strong momentum-dependent electron-
phonon coupling. Structural relaxation yields a commensurate CDW phase characterized by bond-length modulations involving the Mo, N, and F sublattices. We further show that charge doping alone is insufficient to stabilize the soft
phonon, whereas compressive biaxial strain exceeding -3 percent completely suppresses the CDW instability. Electron-
phonon coupling calculations indicate that the CDW phase exhibits a reduced coupling constant lambda = 0.40 and logarithmic
phonon frequency omega_log = 219 K, leading to a low superconducting transition temperature Tc about 1 K. In contrast, the strain-stabilized high-
symmetry phase shows enhanced coupling (lambda = 0.53, omega_log = 272 K) and a higher Tc about 4 K. Our results establish Mo2NF2 as a strain-tunable platform where superconductivity emerges upon suppression of a competing CDW phase, highlighting the crucial role of
lattice control in Janus MXenes.
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Soft Condensed Matter · Cross-listed from physics.flu-dyn
Confined drying of a binary liquid mixture droplet: A quantitative interferometric study under humidity control
Ole Milark, Jean-Baptiste Salmon and Benjamin Sobac
We present a methodology that combines Mach-Zehnder interferometry, a custom relative humidity (RH) controlled chamber, and a confined two-dimensional droplet geometry to enable precise investigations of drying of complex fluids and the associated transport mechanisms. This approach is applied to a model binary mixture, water-glycerol, the concentration-dependent thermodynamic and transport properties of which are relatively well documented. High-resolution interferometric imaging (6 $\mu$m pixel$^{-1}$, 1 frame s$^{-1}$) allows simultaneous measurement of drying kinetics and internal concentration fields with $\pm 0.5\%$ accuracy, characterized here over a wide range of RH (25-95%), and thus Péclet numbers. The experimental results closely match a quasisteady, isothermal model of vapor-
diffusion-controlled evaporation coupled to
diffusion within the droplet. These data enable extraction of both the concentration-dependent mutual
diffusion coefficient $D(\varphi)$ and the water chemical activity $a_w(\varphi)$ over almost the entire range of glycerol volume fraction $\varphi$, even from a single low-RH experiment. While $a_w(\varphi)$ agrees well with literature values, our measurements yield a consistent fit for $D(\varphi)$. Complementary experiments with fluorescence microscopy confirm that buoyancy-driven convection, although present, remains negligible, so that mass
diffusion dominates solute transport in this confined geometry. The overall agreement validates the methodology, demonstrating its robustness as a quantitative framework for probing drying dynamics and transport in complex fluids, with broad applicability to controlled evaporation studies.
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