Materials Science
Accurate atomic correlation and total energies for correlation consistent effective core potentials II: Rb-Xe elements
Aqsa Shaikh, Omar Madany, Benjamin Kincaid et al. (+1 more)
We employ correlation-consistent effective core potentials (ccECPs) to perform exact or nearly exact correlation and total energy calculations for the fifth-row elements (Rb-Xe). Total energies are calculated using various correlated methods: configuration interaction (CI), coupled-cluster (CC) up to perturbative quadruple excitations whenever feasible, and
stochastic quantum Monte Carlo (QMC) approaches. In order to estimate the energy at the complete basis set (CBS) limit, the basis sets are constructed systematically through aug-cc-p(C)VnZ for each ccECP and further extrapolated to the CBS limit within the corresponding methods. Kinetic energies are evaluated at the FCI/CISD level to provide insights into the electron density and localization of the ccECPs. We also provide data sets for widely used
diffusion Monte Carlo (DMC) to quantify fixed-node biases with single-reference trial wavefunctions. These comprehensive
benchmarks validate the accuracy of ccECPs within the CC, CI, and QMC methodologies, thus providing accurate and tested valence-only
Hamiltonians for many-body electronic structure calculations.
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All authors Aqsa Shaikh, Omar Madany, Benjamin Kincaid, Lubos Mitas
Strongly Correlated Electrons
Impact of strong electronic correlations on altermagnets: the case of NiS2
Ina Park, Turan Birol, Antoine Georges et al. (+1 more)
One of the distinguishing features of an altermagnet is that its
spin-up and
spin-down bands display a nodal momentum-dependent splitting even in the absence of
spin-orbit coupling. While this property has been investigated in many weakly-correlated altermagnetic materials, the impact of strong electron-electron interactions on the
spin-dependent electronic structure has remained little explored, particularly in metals. Here, we propose NiS2 as a prototypical strongly correlated metallic altermagnet. While at ambient pressure this compound is an altermagnetic Mott
insulator, it undergoes a pressure-driven metal-
insulator transition (MIT) while maintaining its altermagnetic ordered phase. By systematically comparing DFT, DFT+U, and DFT+DMFT calculations on the metallic altermagnetic phase near the MIT, we disentangle how strong static and dynamic correlations modify the electronic structure. Specifically, the
spin splitting of the bands is modified not only through the enhancement of the local
magnetic moment caused by static correlations, but also by the momentum-dependent bandwidth renormalization caused by dynamic correlations. Moreover, dynamic electronic correlations cause a pronounced lifetime asymmetry between the
spin-up and
spin-down quasiparticles, an effect that is amplified by the particle-hole asymmetry promoted by Hund's correlations. Our results not only shed light on the rich landscape of correlation effects in metallic altermagnets, but also establishes NiS2 as a platform to investigate the interplay between Mott and Hund physics and altermagnetic order.
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All authors Ina Park, Turan Birol, Antoine Georges, Rafael M. Fernandes
Superconductivity
Chronicle: "Foot of the iceberg" of Nobel Prize in Physics 2025: ILTPE and LTP contribution
O. G. Turutanov
The Nobel Prize in Physics 2025 has been awarded to John Clarke, John Martinis, and Michel Devoret for "the discovery of macroscopic
quantum mechanical tunnelling and energy quantisation in an electric
circuit". The paper explains the essence of their studies and shows in a historical context the importance of earlier research in superconductivity and
quantum physics of macroscopic systems by other physicists, particularly, Ukrainian scientists, including employees of the B. Verkin Institute for Low Temperature Physics and Engineering of the NAS of Ukraine (ILTPE). The role of the Fizyka Nyzkykh Temperatur (FNT) journal issued by ILTPE in Kharkiv and its translation as AIP Low Temperature Physics (LTP) in dissemination of results of the theoretical and experimental studies in the field is emphasized as well.
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Soft Condensed Matter
Selective trapping of bacteria in porous media by cell length
David Gao, Zeyuan Wang, Mihika Jain et al. (+2 more)
Bacteria commonly inhabit porous environments such as host tissues, soil, and marine sediments, where complex geometries constrain and redirect their motion. Although bacterial motility has been studied in porous media, the roles of
cell length and pore shape in navigating these environments remain poorly understood. Here, we investigate how
cell morphology and pore architecture jointly determine bacterial spreading behavior. Using genetically engineered E. coli with tunable
cell length, we performed single-
cell tracking in microfluidic devices that mimic ordered and disordered porous structures. We find that elongated bacteria traverse ordered pore networks more effectively than short
cells, exhibiting straighter paths, greater directional persistence, and enhanced exploration efficiency. In contrast, in disordered porous media, elongated bacteria become trapped in dead-end regions for extended periods, resulting in markedly reduced navigational efficiency. Together, these results reveal how
cell shape and environmental geometry interact to govern bacterial transport. Moreover, we suggest a new mechanism for separating antimicrobial-resistant (AMR) bacteria from elongated susceptible
cells in designer porous media.
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All authors David Gao, Zeyuan Wang, Mihika Jain, Arnold J. T. M. Mathijssen, Ran Tao
Strongly Correlated Electrons
Exploring the Kondo Effect in Strained Kagome Nanoribbons
Patricia A Almeida, George B Martins and Sergio Ulloa
Metallic kagome systems have attracted considerable interest in recent years, as they provide a rich platform for studying phenomena associated with their distinctive band structure. The coexistence of bands with Dirac points similar to those in
graphene, along with a completely flat band, makes this an ideal structure for investigating how
lattice symmetries may protect topological and many-body correlation effects. Since applied strain can break
lattice symmetries and modify the electronic structure, understanding how strain influences phenomena such as the Kondo effect in kagome materials may provide essential insights into correlated-electron behavior. We employ the single-
impurity Anderson model and the numerical renormalization group to analyze the Kondo effect in kagome zigzag nanoribbons under uniaxial strain. We find that strain manipulation enables precise control over the strength of the Kondo effect on an
impurity hybridized on the ribbon with different coordination environments, and that symmetric local environments may result in strong suppression of the effective hybridization due to orbital interference. We find that the specific location of the
impurity on the ribbon, especially when the
Fermi energy lies close to weakly dispersive edge states, can lead to significant changes in the characteristic Kondo temperature. Such sensitivity may be used to provide unique information on the local density of states of a system. These results demonstrate that strain is a powerful tuning parameter in kagome nanoribbons, strongly modifying the screening of
magnetic impurities.
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Soft Condensed Matter
Real-space Atomic Dynamics in Liquid Gallium Studied by Inelastic Neutron Scattering
Chengyun Hua, Yadu K. Sarathchandran, Eva Zarkadoula et al. (+4 more)
Gallium is a prototypical
liquid metal and has gained renewed
attention due to its unique properties. Characterizing and elucidating its atomic dynamics remains elusive despite numerous studies, primarily due to the challenges of quantifying atomic-scale dynamics in
liquids. Recent developments in inelastic
neutron scattering enable us to measure the Van Hove correlation function that describes the real-space motion of
liquid atoms. In this work, we use this approach to reveal the dynamics in gallium
liquids and find the co-existence of two dynamical medium-range orders (MROs), which have a dynamical behavior distinct from that of the short-range order (SRO). We propose that these MROs are driven by global forces in the form of two density waves, as a direct consequence of the underlying competition between ionic core repulsion and valence electron cohesion. We suggest that the density wave approach is not only applicable to other metallic
liquids exhibiting similar structural anomalies, but also offers a promising direction for elucidating the dynamics of complex
liquids and glasses by linking electronic-state fluctuations to atomic dynamics.
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All authors Chengyun Hua, Yadu K. Sarathchandran, Eva Zarkadoula, Wojciech Dmowski, Douglas L. Abernathy, Takeshi Egami, Yuya Shinohara
Soft Condensed Matter
Complexity in the medium-range order of gallium as a polyvalent liquid metal
Chengyun Hua, Yadu K. Sarathchandran, Eva Zarkadoula et al. (+4 more)
Simplicity in chemical composition does not always translate into simplicity in the structures and dynamics of
liquids and solids. Some elementary
liquid metals, such as gallium, show unusual behaviors in thermodynamic and transport properties as a result of their complex atomic structure and dynamics. In this work, we study the real-space atomic correlation function of
liquid gallium by
neutron scattering. In the pair-distribution function, there exist two kinds of medium-range order (MRO), characterized by oscillations beyond the first nearest neighbors. On the other hand, the first neighbor shell shows only one kind of bond. The two types of MRO are strongly overlapping in space and fluctuating in time. We propose that they are the basis for anomalous behavior of
liquid gallium. This view challenges the current view that
liquid gallium consists of fluctuating metallic and insulating domains. These findings shed new light on the interpretation of similar microscopic anomalies observed in other semi-metallic
liquids.
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All authors Chengyun Hua, Yadu K. Sarathchandran, Eva Zarkadoula, Wojciech Dmowski, Douglas L. Abernathy, Yuya Shinohara, Takeshi Egami
Strongly Correlated Electrons
Exotic coupled spin-charge states in decorated honeycomb magnets: A hybrid-Monte Carlo study
Satyabrata Jana and Sahinur Reja
We uncover four exotic coupled
spin-charge ground states in the strong coupling limit of the Kondo
lattice model at various electronic fillings on a frustrated decorated honeycomb
lattice, where each regular honeycomb sublattice point is occupied by three-site triangular units. We employ a hybrid Markov Chain Monte Carlo (hMCMC) simulation method which combines classical MCMC for localized
spins and exact diagonalization of the electronic
Hamiltonian. Two of the
spin-charge ground states, respectively consists of three-site and six-site
ferromagnetic (FM) clusters arranged in anti-FM and $120^{\circ}$ Yafet-Kittel (YK) phase which we label as S-AF (super-antiferromagnet) and S-YK (super-YK) respectively. Two even more interesting coupled
spin-charge states, respectively accommodate FM dimers and trimers (as three-site line segment), which we label as FM-D and FM-T. In both cases, the anti-FM aligned dimers and trimers in respective phases, are arranged in stripes along one of three
lattice directions: the spontaneously
symmetry broken phases giving rise to non-trivial macroscopic degeneracy. These underlying
magnetic textures (except S-YK state) restrict electrons in fragmented small regions (e.g, triangular units, two-site dimers, three-site line segments respectively in S-AF, FM-D and FM-T), resulting in flat bands by opening large gaps in electronic density of states, which in turn stabilize these coupled
spin-charge states: a "band effect". These exotic
spin-charge ground states could be relevant to electron-doped
spin-systems resulting from various metal-organic frameworks (MOFs), which have attracted significant
attention to condensed matter physics
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Materials Science
Andrei Shumilin, Sourav Dey, Denisa Coltuneac et al. (+2 more)
The progress of magnonics ultimately depends on material platforms that offer precise control of
spin waves propagation. Here, we put forward a chemical strategy to create locally tunable magnonic
crystals by integrating switchable
spin-crossover (SCO) molecules with 2D van der Waals magnets. Specifically, we investigate from first principles a hybrid molecular/2D
heterostructure formed by [Fe((3,5-(CH3)2Pz)3BH)2] molecules (Fe-pz) deposited on a single-layer of semiconducting CrSBr. We show that Fe-pz molecules are stable on CrSBr while preserving its SCO bistability, particularly in densely packed molecular arrays. By patterning Fe-pz into periodic stripes separated by pristine CrSBr regions, the interface becomes a magnonic
crystal that filters
spin waves at selected frequencies. Crucially, light-driven excited
spin-state trapping (LIESST) enables LS-HS switching and induces up to ~1.3% local strain in CrSBr, which in turn reshapes the magnonic band structure in a dynamic and reversible manner. These results establish Fe-pz@CrSBr as a switchable platform for on-chip, programmable magnonic devices.
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All authors Andrei Shumilin, Sourav Dey, Denisa Coltuneac, Laurentiu Stoleriu, José J. Baldoví
Mesoscale and Nanoscale Physics
Cascade of Spin Moiré Superlattices with In-Plane Field in Triangle Lattice Semimetal EuAg$_4$Sb$_2$
Paul M. Neves, Takashi Kurumaji, Joshua P. Wakefield et al. (+5 more)
EuAg$_4$Sb$_2$ is a rhombohedral europium triangle
lattice material that exhibits a rich phase diagram of
spin moiré superlattices (SMS) and single-$q$
magnetic phases. In this paper, we characterize the incommensurate phases accessible with field applied in the plane with small angle
neutron scattering (SANS). A variety of phases with unusual SANS patterns are accessible with
magnetic field applied along the $a$ and $a^*$ directions. Many of these phases can be understood to be multi-$q$ phases. One phase in particular, ICM2b (ICM=incommensurate
magnetic phase), is rather unconventional in that it is an anisotropic multi-$q$ phase that can rotate freely within the $ab$-plane, dependent on
magnetic field direction and history. The stabilization of tunable multi-$q$ incommensurate
spin textures via in-plane field sets this class of materials apart from conventional skyrmion materials. We further identify that the propagation vectors of the in-plane phases have a significant commensuration with the diameter of the smallest pocket of the
Fermi surface ($2k_{\text{F}}$). The multi/single-$q$ nature is also correlated with the enhancement of resistivity, suggesting that a gap opens in the electron bands at $q=2k_{\text{F}}$. We also compare with a phenomenological model of the phase diagram. The richness of phases revealed in this study hint at the frustrated nature of the incommensurate magnetism present in EuAg$_4$Sb$_2$ and motivate further probes of these phases and the origin of the stability of
spin moiré superlattices. Finally, the coupling of the multi-$q$ nature and $q=2k_{\text{F}}$ commensuration condition reveals the key requirements for a strong SMS transport response.
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All authors Paul M. Neves, Takashi Kurumaji, Joshua P. Wakefield, Chi Ian Jess Ip, Robert Cubitt, Satoru Hayami, Jonathan S. White, Joseph G. Checkelsky
Mesoscale and Nanoscale Physics
Single-$q$ Cycloid and Double-$q$ Vortex Lattices in Layered Magnetic Semimetal EuAg$_4$Sb$_2$
Paul M. Neves, Takashi Kurumaji, Joshua P. Wakefield et al. (+11 more)
Recently, a host of exotic
magnetic textures such as topologically protected skyrmion
lattices has been discovered in several bulk metallic lanthanide compounds. In addition to hosting skyrmion phases, a hallmark of this class of materials is the appearance of numerous
spin textures characterized by a superposition of multi-$q$
magnetic modulations:
spin moiré superlattices. The nuanced energy landscape thus motivates detailed studies to understand the underlying interactions. Here, we comprehensively characterize and model the three zero-field
magnetic textures present in one such material, EuAg$_4$Sb$_2$. Systematic
symmetry breaking experiments using
magnetic field and strain determine that the ground state incommensurate
magnetic phase (ICM1) is single-$q$. In contrast, ICM2 and ICM3 are both double-$q$, i.e.,
spin moiré superlattices. Further, through application of polarized small angle
neutron scattering and spherical
neutron polarimetry, we demonstrate that ICM1 is a single-$q$ cycloid and ICM2 and ICM3 are double-$q$
vortex lattices, with Eu moments lying in the $ab$-plane in zero field and with a
ferromagnetic component at finite field. Despite the quasi-2D nature of EuAg$_4$Sb$_2$, the modulations propagate out of the ab-plane, leading to a shift of the
spin texture between triangle
lattice planes. Further, the ICM3 to ICM2 transition includes an unusual 45$^\circ$ rotation of the
magnetic vortex lattice. Motivated by the coexistence of such drastically different phases in this compound, we conclude by developing a phenomenological model to understand the stability of these states. Our experimental probes and theoretical modeling definitively characterize three different and tunable phases in one material, and provide insight for the design of new topological
spin-texture materials.
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All authors Paul M. Neves, Takashi Kurumaji, Joshua P. Wakefield, Arno Hiess, Paul Steffens, Navid Qureshi, Robert Cubitt, Lisa M DeBeer-Schmitt, Johanna C. Palmstrom, Satoru Hayami, Marek Bartkowiak, Markus Zolliker, Jonathan S. White, Joseph G. Checkelsky
Mesoscale and Nanoscale Physics
A.A. Burkov
We discuss the
quantum geometric contribution to the
diffusion constant and the DC conductivity in metals and semimetals with linear Dirac dispersion. We demonstrate that, for systems with perfectly linear dispersion, there exists a clear and rigorous separation of the
quantum geometric from the ordinary band velocity contributions to the
diffusion constant, which turns out to be directly related to the separation of a rank two tensor into transverse and longitudinal parts. We also demonstrate that, within the self-consistent Born approximation and for Gaussian-distributed disorder, the
diffusion constant of three-dimensional Dirac
fermions at charge neutrality is entirely
quantum geometric in origin, which is not the case for two-dimensional Dirac
fermions. This is the result of an accidental perfect cancellation of the band velocity contribution in three dimensions.
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Mesoscale and Nanoscale Physics
Machine learning assisted high throughput prediction of moiré materials
Daniel Kaplan, Alexander C. Tyner, Eva Y. Andrei et al. (+1 more)
The world of 2D materials is rapidly expanding with new discoveries of stackable and twistable layered systems composed of
lattices of different
symmetries, orbital character, and structural motifs. Often, however, it is not clear a priori whether a pair of monolayers twisted at a small angle will exhibit correlated or interaction-driven phenomena. The computational cost to make accurate predictions of the single particle states is significant, as small twists require very large unit
cells, easily encompassing 10,000 atoms, and therefore implementing a high throughput prediction has been out of reach. Here we show a path to overcome this challenge by introducing a machine learning (ML) based methodology that efficiently estimates the twisted interlayer tunneling at arbitrarily low twist angles through the local-configuration based approach that enables interpolating the local stacking for a range of twist angles using a random forest regression
algorithm. We leverage the kernel
polynomial method to compute the density of states (DOS) on large real space graphs by reconstructing a
lattice model of the twisted
bilayer with the ML fitted hoppings. For twisted
bilayer graphene (TBG), we show the ability of the method to resolve the magic angle DOS at a substantial improvement in computational time. We use this new technique to scan through the database of stable 2D monolayers (MC2D) and reveal new twistable candidates across the five possible points groups in two-dimensions with a large DOS near the
Fermi energy, with potentially exciting interacting physics to be probed in future experiments.
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All authors Daniel Kaplan, Alexander C. Tyner, Eva Y. Andrei, J. H. Pixley
Strongly Correlated Electrons
Exciton interacting with the phonons of an electronic Wigner crystal
Jens Havgaard Nyhegn, Esben Rohan Christensen and Georg M. Bruun
With the advent of atomically thin and tunable van der Waals materials, a two-dimensional electronic Wigner
crystal has recently been observed. The smoking gun signal was the appearance of an umklapp branch in optical
exciton spectroscopy coming from the periodic potential generated by the Wigner
crystal assumed to be static. Vibrations of the Wigner
crystal however leads to a gapless
phonon spectrum, which may affect the
exciton spectrum. To explore this, we develop a field theoretical description of an
exciton interacting with electrons forming a Wigner
crystal including the coupling to the
phonons. We show that importance of the
exciton-
phonon coupling scales with the
exciton-electron interaction strength relative to the typical
phonon energy squared. The motion of the
exciton leads to two kinds of scattering processes, where the
exciton emits a
phonon either staying within the same Bloch band (intraband scattering) or changing its band (interband scattering). Using a non-perturbative self-consistent Born approximation, we demonstrate that these scattering processes lead to the formation of quasiparticles (polarons) consisting of the
exciton in Bloch states dressed by Wigner
crystal phonons. The energy shift and damping of these polarons depend on the electron density in a non-trivial way since it affects both the
exciton-
phonon interaction strength, as well as the
phonon and
exciton spectra. In particular, the damping is strongly affected by whether the polaron energy is inside the gapless
phonon scattering continuum or not. Using these results, we finally analyse their effects on the observed spectral properties of the
exciton.
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Statistical Mechanics · Cross-listed from quant-ph
Many-body contextuality and self-testing quantum matter via nonlocal games
Oliver Hart, David T. Stephen, Evan Wickenden et al. (+1 more)
Contextuality is arguably the fundamental property that makes
quantum mechanics different from classical physics. It is responsible for
quantum computational speedups in both magic-state-injection-based and measurement-based models of computation, and can be directly probed in a many-body setting by multiplayer nonlocal
quantum games. Here, we discuss a family of games that can be won with certainty when performing single-site Pauli measurements on a state that is a codeword of a Calderbank-Shor-Steane (CSS) error-correcting
quantum code. We show that these games require deterministic computation of a code-dependent Boolean function, and that the classical probability of success is upper bounded by a generalized notion of nonlinearity/nonquadraticity. This success probability quantifies the state's contextuality, and is computed via the function's (generalized) Walsh-Hadamard spectrum. To calculate this, we introduce an efficient, many-body-physics-inspired method that involves identifying the
symmetries of an auxiliary hypergraph state. We compute the classical probability of success for several paradigmatic CSS codes and relate it to both classical statistical mechanics models and to strange correlators of
symmetry-protected topological states. We also consider CSS submeasurement games, which can only be won with certainty by sharing the appropriate codeword up to local isometries. These games therefore enable self-testing, which we illustrate explicitly for the 2D toric code. We also discuss how submeasurement games enable an extensive notion of contextuality in many-body states.
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All authors Oliver Hart, David T. Stephen, Evan Wickenden, Rahul Nandkishore
Soft Condensed Matter
Polar chiral active matter as a motile, disordered Josephson array: Information supercurrents and Goldstone spin waves
Magnus F Ivarsen
We consider a minimalist model of polar
chiral active matter: overdamped, self-propelled
agents coupled through a localized Kuramoto–Sakaguchi interaction, which causes
alignment. Intrinsic frustration drawn from a broad distribution constitutes a temperature for the ensemble. In the co-moving frame of the local order parameter, the
agent dynamics reduce exactly to the Adler equation, placing each
agent in a tilted washboard potential: trapped
agents are phase-synchronized, and we demonstrate thereby that synchronization (phase
rigidity) is maintained by information supercurrents;
agents that are running in this potential form a resistive bath. The model is therefore formally isomorphic to a disordered, resistively shunted Josephson array, and a Monte-Carlo sweep over the frequency dispersion empirically recovers the disorder-broadened Adler–Ohmic crossover of the ensemble-averaged slip velocity. Lifting the dynamics from $S^1$ to $S^2$, the polar
alignment torque (the Kuramoto-term) is geometrically equivalent to the Gilbert-damping term of the Landau–Lifshitz–Gilbert equation; the mapping establishes an effortless azimuthal precession, yielding a Goldstone-mode dispersion that carries an effective inertia $\propto R^2$, where $R$ is the local order parameter. This furnishes a microscopic basis for the
spin-wave transport assumed in inertial-
spin models of flocking. Within its regime of validity, i.e., dry, polar,
chiral agents under marginal synchronization with sufficient frustration, the model is well-described as a dissipative spintronic fluid.
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Materials Science · Cross-listed from physics.chem-ph
A Cartesian-3j Framework for Machine Learning Interatomic Potentials
Zemin Xu, Chenyu Wu, Wenbo Xie et al. (+1 more)
Machine learning interatomic potentials (MLIPs) have brought substantial gains in the extrapolation capability in computational chemistry. However, most equivariant models are typically built with spherical tensors (STs), while Cartesian tensor formulations remain less developed despite their natural
alignment with atomic coordinates and tensorial targets. In this work, we develop a Cartesian framework for irreducible Cartesian tensors (ICTs) by introduce the Cartesian-3j symbol and Cartesian Generalized Clebsch-Gordan Coefficients, which serve as direct analogues of the Wigner-3j symbol and Generalized Clebsch-Gordan coefficients defined for ST coupling. We extend the e3nn library to support ICT product, and use this framework to build Cartesian counterparts of MACE, NequIP, and Allegro, allowing the first controlled comparison where architectures are held fixed and only the tensor basis is changed. Our experiments show that irreducible Cartesian models can achieve accuracy comparable to spherical counterparts, but direct Cartesianization incurs unfavorable compute and
memory scaling, motivating dedicated Cartesian architectural choices. Leveraging ICTs and our framework, we introduce TACE-v1-OAM-M and demonstrate that it achieves competitive performance on Matbench Discovery compared to state-of-the-art ST models.
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All authors Zemin Xu, Chenyu Wu, Wenbo Xie, P. Hu
Other Condensed Matter · Cross-listed from quant-ph
Random purification channel for passive Gaussian bosons
Francesco Anna Mele, Filippo Girardi, Senrui Chen et al. (+2 more)
The random purification channel, which, given $n$ copies of an unknown mixed state $\rho$, prepares $n$ copies of an associated random purification, has proved to be an extremely valuable tool in
quantum information theory. In this work, we construct a Gaussian version of this channel that, given $n$ copies of a bosonic passive Gaussian state, prepares $n$ copies of one of its randomly chosen Gaussian purifications. The construction has the additional advantage that each purification has a mean
photon number which is exactly twice that of the initial state. Our construction relies on the characterisation of the commutant of passive Gaussian
unitaries via the representation theory of dual reductive pairs of
unitary groups.
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All authors Francesco Anna Mele, Filippo Girardi, Senrui Chen, Marco Fanizza, Ludovico Lami
Materials Science · Cross-listed from physics.chem-ph
Multimer Embedding for Molecular Crystals Utilizing up to Tetramer Interactions
Alexander List, A. Daniel Boese and Johannes Hoja
Molecular
crystals possess a highly complex crystallographic landscape which in many cases results in the experimental observation of multiple
crystal structures for the same compound. Accurate results can often be obtained for such systems by employing periodic density functional theory using hybrid functionals; however, this is not always computationally feasible. One possibility to circumvent these expensive periodic calculations is the utilization of multimer
embedding methods. Therein, the fully periodic
crystal is described at a lower level of theory, and subsequently monomer energies, dimer interaction energies, etc. are corrected via high-level calculations. In this paper, we further extend such a multimer
embedding approach by one multimer order for all investigated properties, allowing us to compute
lattice energies up to the tetramer
embedding level, and atomic forces, the stress tensor, and harmonic
phonons up to the trimer level. We test the significance of including these higher-order multimers by
embedding PBE0+MBD multimers into periodic PBE+MBD calculations utilizing the X23
benchmark set of molecular
crystals and comparing the results to explicit periodic PBE0+MBD calculations. We show that tetramer interactions systematically improve the
lattice energy approximation and explore multiple possibilities for multimer selection. Furthermore, we confirm that trimer interactions are crucial for the description of the stress tensor, yielding
cell volumes within 1 % of those of PBE0+MBD. Subsequently, this also results in an improvement of the description of vibrational properties, giving on average gamma point frequencies within 1.3 wave numbers and vibrational free energies within 0.3 kJ/mol of the PBE0+MBD results.
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Other Condensed Matter
Photonics of topological magnetic textures
Vakhtang Jandieri, Ramaz Khomeriki, Daniel Erni et al. (+4 more)
Topological textures in magnetically ordered materials are important case studies for fundamental research with promising applications in data science. They can also serve as photonic elements to mold electromagnetic fields endowing them with features inherent to the
spin order, as demonstrated analytically and numerically in this work. A self-consistent theory is developed for the interaction of spatially structured electromagnetic fields with non-collinear, topologically non-trivial
spin textures. A tractable numerical method is designed and implemented for the calculation of the formed
magnetic/photonic textures in the entire simulation space. Numerical illustrations are presented for scattering from point-like singularities, i.e. Bloch points, in the magnetization vector fields, evidencing that the geometry and
topology of the
magnetic order results in photonic fields that embody orbital angular momentum, chirality as well as magnetoelectric densities. Features of the scattered fields can serve as a fingerprint for the underlying
magnetic texture and its dynamics. The findings point to the potential of topological
magnetic textures as a route to molding photonic fields.
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All authors Vakhtang Jandieri, Ramaz Khomeriki, Daniel Erni, Nicolas Tsagareli, Qian Li, Douglas H. Werner, Jamal Berakdar
Strongly Correlated Electrons
Wiedemann-Franz violation and thermal Hall effect in kagome metal TbCr6Ge6
Jhinkyu Choi, Mohan B. Neupane, L. H. Vilela-Leão et al. (+5 more)
The thermal
Hall effect has emerged as a powerful probe of exotic excitations in correlated
quantum materials, providing access to charge-neutral heat carriers that remain invisible to electrical transport. To directly examine how heat and charge respond in relation within a kagome metal, we investigate the ferrimagnetic rare-earth 1-6-6 compound TbCr6Ge6 using the Wiedemann-Franz (WF) framework. We observe a dramatic breakdown of the WF law across the ferrimagnetic transition, where both longitudinal and transverse Lorenz ratios, L_{xx,xy} = \kappa_{xx,xy} / (T \sigma_{xx,xy}), deviate strongly from the Sommerfeld value L_0. After a partial recovery toward L_0 near 5-7 K, the Lorenz ratios are sharply suppressed well below L_0 despite a metallic charge response. We further find a pronounced low-temperature suppression of both L_{xx} and L_{xy} and a sign-changing transverse Lorenz ratio, indicating a clear decoupling between heat and charge transport and signaling substantial contributions from charge-neutral excitations whose Berry-
curvature-driven transverse response evolves with temperature and
magnetic field. TbCr6Ge6 thus provides a tunable metallic platform in which exchange-driven ferrimagnetism governs both longitudinal and transverse thermal responses, enabling controlled departures from Wiedemann-Franz behavior over an experimentally accessible temperature and field range.
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All authors Jhinkyu Choi, Mohan B. Neupane, L. H. Vilela-Leão, Bishnu P. Belbase, Arjun Unnikrishnan, Syeda Neha Zaidi, Jukka I. Väyrynen, Arnab Banerjee
Statistical Mechanics
Random planting with harvest: A statistical-mechanical analysis
Julian Talbot
We formulate a statistical-mechanical description of a recently introduced random planting model in which plants are represented by growing hard disks. Seedlings of negligible size are introduced at random positions in a field, grow at a prescribed rate, and are harvested upon reaching a fixed maturity diameter. Planting attempts that would lead to an overlap at any time during growth are rejected. Starting from an empty field, this simple dynamical rule drives the system to a nonequilibrium steady state in which the mean planting and harvesting rates coincide. We show that the steady state can be mapped onto a nonadditive polydisperse hard-disk fluid and exploit this mapping to develop analytical predictions based on a low-density virial expansion and on scaled particle theory. The resulting description yields an effective adsorption isotherm for the steady-state plant density as a function of the planting rate and compares favorably with numerical simulations over a wide range of parameters. At large planting rates, the density approaches the optimal value achieved by desynchronized regular planting, and the data are consistent with an algebraic approach to this limit with an exponent close to 1/3. Beyond density and yield, we show that the spatial organization of the field at high planting rates exhibits clear signatures of the same underlying
geometric constraints that characterize optimal desynchronized planting. This connection is revealed through both the conventional radial distribution function and a radius-resolved pair correlation g(z,r) which highlights strong size correlations associated with parent-child seeding events and whose structure can be interpreted as a dynamically broadened precursor of the corresponding ideal mixe–size
lattice. Finally, we extend the theory to sigmoidal growth laws and compute the associated virial coefficient.
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Mesoscale and Nanoscale Physics
Signatures of real-space geometry, topology, and metric tensor in quantum transport in periodically corrugated spaces
Benjamin Schwager, Theresa Appel and Jamal Berakdar
The motion of a
quantum particle constrained to a two-dimensional non-compact Riemannian
manifold with non-trivial metric can be described by a flat-space Schroedinger-type equation at the cost of introducing local mass and metric and geometry-induced effective potential with no classical counterpart. For a metric tensor periodically modulated along one dimension, the formation of bands is demonstrated and transport-related quantities are derived. Using S-
matrix approach, the
quantum conductance along the
manifold is calculated and contrasted with conventional
quantum transport methods in flat spaces. The
topology, e.g. whether the
manifold is simply connected, compact or non-compact shows up in global, non-local properties such as the Aharonov-Bohm phase. The results vividly demonstrate emergent phenomena due to the interplay of reduced-dimensionality, particles
quantum nature, geometry, and
topology.
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Mesoscale and Nanoscale Physics · Cross-listed from physics.ins-det
A MAPS Detector for High Resolution Low Dose EBSD
Barnaby D.A. Levin, Kalani Moore, Nicolò M. Della Ventura et al. (+3 more)
The use of highly sensitive pixelated direct detectors has dramatically improved the performance of high energy instrumentation such as transmission electron microscopy. Here, we describe a recently developed monolithic active pixel sensor designed for low energy scanning electron microscopy applications. This detector enables electron backscatter diffraction (EBSD) at lower energies and dose than are accessible with existing scintillator-coupled detectors, expanding grain orientation mapping capabilities to materials such as ceramics that are poor electron conductors. The high detector sensitivity allows collection of rich diffraction information - providing dislocation defect contrast that is otherwise not accessible via EBSD. Indeed, even the energy of single electron interaction events can be measured with this detector, which we demonstrate to energy filter diffraction patterns revealing details of how diffraction occurs at low energy.
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All authors Barnaby D.A. Levin, Kalani Moore, Nicolò M. Della Ventura, McLean P. Echlin, Tresa M. Pollock, Daniel S. Gianola
Strongly Correlated Electrons
Revival Dynamics from Equilibrium States: Scars from Chords in SYK
Debarghya Chakraborty and Dario Rosa
We develop a novel framework to build
quantum many-body scar states in bipartite systems characterized by perfect correlation between the
Hamiltonians governing the two sides. By means of a Krylov construction, we build an interaction term which supports a tower of equally-spaced energy eigenstates. This gives rise to finite-time revivals whenever the system is initialized in a purification of a generic
equilibrium state. The dynamics is universally characterized, and is largely independent of the specific details of the
Hamiltonians defining the individual partitions. By considering the two-sided chord states of the double-scaled SYK model, we find an approximate realization of this framework. We analytically study the revival dynamics, finding rigid motion for wavepackets localized on the spectrum of a single SYK copy. These findings are tested numerically for systems of finite size, showing excellent agreement with the analytical predictions.
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Strongly Correlated Electrons
Optimal array geometries for kinetic magnetism and Nagaoka polarons
N. Hernandez-Cepeda and Sergio E. Ulloa
Quantum dot (QD) platforms have enabled the direct observation of Nagaoka ferromagnetism (NFM) in small arrays and non-infinite interaction strength. However, optimizing the cluster connectivity characteristics that yield a ground state with maximal
spin and their robustness against
magnetic fields remains unexplored. Employing exact diagonalization of the Hubbard
Hamiltonian, we find a connection between the existence of kinetic ferromagnetism and graph theory descriptions. Algebraic connectivity ($\lambda_2$) and Katz centrality (KC) are shown to be related to the
spin-correlation over the system. In square arrays, the onset of NFM is found to be $t_c/U\simeq \lambda_2^2$. In optimal cluster geometries, large $\lambda_2$ and low KC fluctuation per site are found to enhance $t_c/U$, extending the NFM phase while diminishing the strength of
spin correlation clouds. A perpendicular
magnetic field introduces Aharonov-Bohm phases, and a critical flux for which NFM is destroyed. We further find that tuning the flux phase to $\pi$ results in a ground state that exhibits
antiferromagnetic correlations (counter-Nagaoka state). Our results illustrate how NFM and polaron formation can be predicted from the array's connectivity ($\lambda_2$ and KC), and how the introduction of flux results in the counterintuitive destruction of kinetic ferromagnetism in the system.
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Strongly Correlated Electrons
Two-dimensional coherent spectroscopy of CoNb$_2$O$_6$
Yoshito Watanabe, Simon Trebst and Ciarán Hickey
With recent advances in terahertz (THz) sources and detection, two-dimensional coherent spectroscopy (2DCS), which allows to probe nonlinear responses in a two-frequency plane, now reaches the meV regime relevant for quasiparticle excitations in
magnetic materials. This opens a promising route to reveal many-body phenomena that evade linear-response probes. To date most experimental applications have focused on classical magnets, and a solid demonstration in a
quantum magnet has yet to be established. Here we present a theoretical study of 2DCS in CoNb$_2$O$_6$, a quasi-one-dimensional Ising magnet that is believed to host fractionalized spinons which at low temperatures are confined by weak interchain coupling. Our analysis, which builds on an effective $S=1/2$
Hamiltonian is found to reveal unambiguous 2DCS signatures of spinon deconfinement above the low-temperature ordered phase. Using a four-spinon approximation, we track these 2DCS signatures by sequentially building a faithful microscopic model for CoNb$_2$O$_6$, starting from the exactly solvable one-dimensional transverse-field Ising model (1$d$ TFIM) and successively adding interactions to capture its key low-energy physics. In particular, adding a bond-dependent staggered YZ interaction to the 1$d$-TFIM already reproduces many key spectral features of the full material
Hamiltonian. Within this TFIM+YZ model, we find a series of bound states, including a four-spinon bound state that is distinct from the familiar two-spinon bound states. We further find that introducing a confinement potential suppresses sharp spinon-echo features in the two-frequency space, which are thought to reflect an underlying continuum of fractionalized excitations. Our results provide concrete predictions and clear targets for future THz 2DCS experiments on CoNb$_2$O$_6$ and related quasi-one-dimensional
quantum magnets.
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Superconductivity
Wen Li, Vahid Hassanzade, Maxim Dzero et al. (+1 more)
We study
spin-triplet superconductivity with both
unitary and nonunitary pairing in the presence of an external Zeeman
magnetic field. Within a mean-field framework, we exactly diagonalize the Bogoliubov-de Gennes
Hamiltonian and derive general expressions for the quasiparticle spectrum, superconducting gap, critical temperature, and
spin magnetization, valid for arbitrary
magnetic-field strengths and temperatures. We analyze in detail the nonlinear
spin susceptibility and the field
evolution of the superconducting gap and transition temperature, highlighting qualitative differences between
unitary and nonunitary pairing states. Our results are broadly applicable to a wide range of materials, including systems with both weak and strong
spin-orbit coupling. We show that systematic measurements of the critical temperature and
spin susceptibility as functions of the magnitude and orientation of the
magnetic field provide a powerful means to identify the structure of the
spin-triplet order parameter, and we discuss implications of our findings for candidate materials such as 4Hb-TaS$_2$ and PrOs$_4$Sb$_{12}$.
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All authors Wen Li, Vahid Hassanzade, Maxim Dzero, Vladyslav Kozii
Mesoscale and Nanoscale Physics · Cross-listed from quant-ph
Numerically exact open quantum system work statistics with process tensors
Mike Shubrook, Moritz Cygorek, Erik Gauger et al. (+2 more)
Accurately quantifying the thermodynamic work costs of
quantum operations is essential for the continued development and optimisation of emerging
quantum technologies. This present a significant challenge in regimes of rapid control within complex, non-
equilibrium environments - conditions under which many contemporary
quantum devices operate and conventional approximations break down. Here, we introduce a process tensor framework that enables the computation of the full numerically exact
quantum work statistics of driven open
quantum systems. We demonstrate the utility of our approach by applying it to a Landauer erasure protocol operating beyond the weak-coupling, Markovian, and slow-driving limits. The resulting work probability distributions reveal distinct
quantum signatures that are missed by low-order moments yet significantly impact the erasure fidelity of the protocol. Our framework delivers non-perturbative accuracy and detail in characterising energy-exchange fluctuations in driven open
quantum systems, establishing a powerful and versatile tool for exploring thermodynamics and control in the operating regimes of both near-term and future
quantum devices.
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All authors Mike Shubrook, Moritz Cygorek, Erik Gauger, Jake Iles-Smith, Ahsan Nazir
Materials Science
Thermodynamical study of N$_2$ clathrate hydrate from DFT calculations
L. Martin-Gondre, V. Meko Fotso, C. Métais et al. (+3 more)
Thermodynamic stability of N$_2$ clathrate hydrates in the sI and sII structures is investigated using density functional theory with several exchange-correlation functionals, explicitly accounting for composition (cage occupancies) and pressure at T = 0 K. Among the tested functionals, revPBE-D3(0) best reproduces experimental
lattice parameters and bulk
moduli B$_0$ . Energetic analyses confirm the strong impact of large cage double occupancy on sI, whereas the convex-hull results show that sI with single occupancy remains thermodynamically stable up to $\sim$ 0.8 GPa alongside sII with single occupancy. Increasing pressure then stabilizes sII with double occupancy, consistent with its larger large-cage volume and lower framework strain. These results provide a coherent, first-principles thermodynamic framework for N$_2$ hydrate stability and a baseline for finite-temperature extension.
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All authors L. Martin-Gondre, V. Meko Fotso, C. Métais, A. Patt, J. Ollivier, A. Desmedt