CMP Journal 2025-01-21
Statistics
Physical Review Letters: 4
Physical Review X: 1
arXiv: 43
Physical Review Letters
Fast Radio Bursts as Precursor Radio Emission from Monster Shocks
Research article | Collisionless shock in plasma | 2025-01-21 05:00 EST
A. Vanthieghem and A. Levinson
Powerful shock waves around magnetized neutron stars may be the source of mysterious radio bursts that are observed across the sky.
Phys. Rev. Lett. 134, 035201 (2025)
Collisionless shock in plasma, Magnetohydrodynamic waves, Transient & explosive astronomical phenomena, Magnetized plasma, Neutron stars & pulsars, Particle-in-cell methods
Switching Spin Filling Sequence in a Bilayer Graphene Quantum Dot through Trigonal Warping
Research article | Coulomb blockade | 2025-01-21 05:00 EST
Guo-Quan Qin, Fang-Ming Jing, Tian-Yue Hao, Shun-Li Jiang, Zhuo-Zhi Zhang, Gang Cao, Xiang-Xiang Song, and Guo-Ping Guo
In graphene quantum dots with only a few electrons, a triangular distortion of the energy bands near specific points in the hexagonal Brillouin zone makes it possible to control the spin degree of freedom.
Phys. Rev. Lett. 134, 036301 (2025)
Coulomb blockade, Quantum transport, Valley degrees of freedom, Bilayer graphene, Quantum dots
Dynamics of Microscale and Nanoscale Systems in the Weak-Memory Regime
Research article | Brownian motion | 2025-01-21 05:00 EST
Kay Brandner
For dynamical systems in the weak-memory regime, a unique local approximation of the original nonlocal dynamics becomes arbitrarily accurate at long times.
Phys. Rev. Lett. 134, 037101 (2025)
Brownian motion, Dissipative dynamics, Open quantum systems, Quantum thermodynamics, Stochastic processes, Stochastic thermodynamics, Biomolecules, Nonequilibrium systems, Langevin equation, Master equation, Non-Markovian processes
Nonmonotonic Constitutive Curves and Shear Banding in Dry and Wet Granular Flows
Research article | Granular flows | 2025-01-21 05:00 EST
Christopher Ness and Suzanne M. Fielding
We use particle simulations to map comprehensively the shear rheology of dry and wet granular matter comprising particles of finite stiffness, in both fixed pressure and fixed volume protocols. At fixed pressure we find nonmonotonic constitutive curves that are shear thinning, whereas at fixed volume we find nonmonotonic constitutive curves that are shear thickening. We show that the presence of one nonmonotonicity does not imply the other. Instead, there exists a signature in the volume fraction measured under fixed pressure that, when present, ensures nonmonotonic constitutive curves at fixed volume. In the context of dry granular flow we show that gradient and vorticity bands arise under fixed pressure and volume, respectively, as implied by the constitutive curves. For wet systems our results are consistent with a recent experimental observation of shear thinning at fixed pressure. We furthermore predict discontinuous shear thickening in the absence of critical load friction.
Phys. Rev. Lett. 134, 038201 (2025)
Granular flows, Rheology, Suspensions, Shear thickening, Shear thinning
Physical Review X
Nonreciprocal Synchronization of Active Quantum Spins
Research article | Nonequilibrium statistical mechanics | 2025-01-21 05:00 EST
Tobias Nadolny, Christoph Bruder, and Matteo Brunelli
A model of nonreciprocal interactions among quantum spins reveals the emergence of persistent, collective dynamics analogous to a never-ending chase-and-escape motion among the spins.
Phys. Rev. X 15, 011010 (2025)
Nonequilibrium statistical mechanics, Open quantum systems, Synchronization, Atomic ensemble, Quantum many-body systems, PT-symmetry, Lindblad equation, Pattern formation, Theories of collective dynamics & active matter
arXiv
Phase-space Generalized Brillouin Zone for spatially inhomogeneous non-Hermitian systems
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-01-20 20:00 EST
Qingya Li, Hui Jiang, Ching Hua Lee
The generalized Brillouin zone (GBZ) has been highly successful in characterizing the topology and band structure of non-Hermitian systems. However, its applicability has been challenged in spatially inhomogeneous settings, where the non-locality of non-Hermitian pumping competes with Wannier-Stark localization and quantum interference, potentially leading to highly non-exponential state accumulation. To transcend this major conceptual bottleneck, we develop a general phase-space GBZ formalism that encodes non-Bloch deformations in both position and momentum space, such as to accurately represent spatially inhomogeneous non-Hermitian pumping. A key new phenomenon is the bifurcation of the phase-space GBZ branches, which allows certain eigenstates to jump abruptly between different GBZ solutions at various points in real space. The freedom in the locations of such jumps opens up an emergent degree of freedom that protects the stability of real spectra and, more impressively, the robustness of a new class of topological zero modes unique to GBZ this http URL response from these novel spectral and GBZ singularities can be readily demonstrated in mature metamaterial platforms such as photonic crystals or circuit arrays, where effective real-space hoppings can be engineered in a versatile this http URL framework directly generalizes to more complicated unit cells and further hoppings, opening up a vast new arena for exploring unconventional spectral and topological transitions as well as GBZ fragmentation in spatially inhomogeneous non-Hermitian settings.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Hydrodynamic Equations for a system with translational and rotational dynamics
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-01-20 20:00 EST
Akira Yoshimori, Shankar P. Das
We obtain the equations of fluctuating hydrodynamics for many-particle systems whose microscopic units have both translational and rotational motion. The orientational dynamics of each element are studied in terms of the rotational Brownian motion of a corresponding fixed-length director ${\bf u}$. The time evolution of a set of collective densities ${\hat{\psi}}$ is obtained as an exact representation of the corresponding microscopic dynamics. For the Smoluchowski dynamics, noise in the Langevin equation for the director ${\bf u}$ is multiplicative. We obtain that the equation of motion for the collective number-density has two different forms, respectively, for the Ito and Stratonvich interpretation of the multiplicative noise in the ${\bf u}$-equation. Without the ${\bf u}$ variable, both reduce to the Standard Dean-Kawasaki form. Next, we average the microscopic equations for the collective densities ${\hat{\psi}}$ (which are, at this stage, a collection of Dirac delta functions) over phase space variables and obtain a corresponding set of stochastic partial differential equations for the coarse-grained densities ${\psi}$ with smooth spatial and temporal dependence. The coarse-grained equations of motion for the collective densities ${\psi}$ constitute the fluctuating non-linear hydrodynamics for the fluid with both rotational and translational dynamics. From the stationary solution of the corresponding Fokker-Planck equation, we obtain a free energy functional ${\cal F}[\psi]$ and demonstrate the relation between the ${\cal F}[\psi]$s for different levels of the FNH descriptions with its corresponding set of ${\psi}$.
Statistical Mechanics (cond-mat.stat-mech)
45 pages
Wave dynamics in a macroscopic square artificial spin ice
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-01-20 20:00 EST
L. Scafuri, D. A. Bozhko, E. Iacocca
A macroscopic square artificial spin ice, or macro-ASI, is a collection of bar magnets placed in a square lattice arrangement. Each magnet is supported by hinges that allow their mechanical rotation. Previous investigations in these structures have shown ground-state configurations and driven dynamics similar to those of their nanosized counterparts. Here, we numerically investigate the impact of a defect, a Dirac string, on the driven dynamics. We find that waves quickly lose coherence by scattering between modes in this system. In addition, we observe a distinct mode associated with the isolated oscillation of the Dirac string. As expected from spatial localization, this resonant mode is under the band of propagating waves in the macro-ASI. The results are analogous to the development of low-frequency edge modes in nanoscopic spin ices in the presence of defects. Our results provide valuable insight into the physics of mechano-magnetic systems, demonstrating the existence of wave scattering and spatial confinement phenomena in macro-ASIs.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Quantitative analysis of vectorial torques in thin 3d Co ferromagnet using orbital-spin conversion
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-01-20 20:00 EST
B. Bony, S. Krishnia, Y. Xu, S. Collin, A. Fert, J.-M. George, M. Viret, V. Cros, H. Jaffrès
Recent findings in orbitronics pointed out large current-induced torques originating, in the current understanding, from incident orbital currents. These are generated by orbital Rashba-Edelstein effect (OREE) produced at the interface between some light metal and oxides films e.g. by naturally oxidized copper layer (Cu\ast). In the present work, by using second harmonic Hall techniques, we determine the ratio of orbital vs spin currents exerting torques on thin transition metals Co ferromagnet in systems using an orbit-to-spin Pt converter as interlayer with Cu\ast. Our results quantifying damping like torques show that both orbital and spin currents are enhanced in these systems. Moreover, the experimental determination of the decoherence length in a sample series with varying Co thickness clearly demonstrates the interfacial generation of the orbital currents in Cu\ast by Orbital Rashba-Edelstein effects (REE) leading to subsequent magnetic torque in Co over a typical lengthscale of several nanometers
Materials Science (cond-mat.mtrl-sci), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
9 pages (two column), 6 figures, 60 references
A coreless giant vortex in a very strongly dipolar condensate of NaCs molecules
New Submission | Quantum Gases (cond-mat.quant-gas) | 2025-01-20 20:00 EST
A strongly dipolar $^{164}$Dy condensate of dipolar length $a_{\mathrm{dd}}=130.8a_0$, with $a_0$ the Bohr radius, hosts a wide variety of eigenstates, such as droplet, droplet-lattice, and ring-topology states, and self-bound droplets. Motivated by the observation of a very strongly dipolar condensate of NaCs molecules [Bigagli N et al. 2024 Nature 631 289], we demonstrate by numerical simulation, using an improved mean-field model, including the Lee-Huang-Yang interaction, that in a very strongly dipolar NaCs condensate with $a_{\mathrm{dd}} = 2000a_0$, most of the above-mentioned states continue to exist and can appear for a much smaller number $N$ of particles ($N \lessapprox 1000$) within the present experimental possibility. However, in a single-component harmonically-trapped rotating NaCs condensate, a new type of coreless giant-vortex states, with a phase drop of $2 \pi L$ along a closed path around the axis of rotation, appear, where $L$ is the angular momentum of the vortex.
Quantum Gases (cond-mat.quant-gas)
Magnetic-field effect on excitonic condensation emergent in extended Falicov-Kimball model
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-01-20 20:00 EST
We investigate the effects of magnetic fields on excitonic condensation in the extended Falicov-Kimball model, which is a spinless two-orbital Hubbard model with orbital splitting. In lattice systems under magnetic fields up to several tens of teslas, Zeeman effects on electron spins have been extensively studied, while the impact on orbital motion has often been considered negligible. However, the recent capability to generate ultra-high magnetic fields exceeding 1000 T has renewed interest in understanding their influence on ordered phases in correlated electron systems, beyond spin-related phenomena. To examine these effects, we incorporate a magnetic field into the extended Falicov-Kimball model by introducing the Peierls phase into the transfer integrals, enabling the study of orbital motion. Using the Hartree-Fock approximation, we reveal a nonmonotonic response of the excitonic order parameter to increasing magnetic fields. At sufficiently high fields, the excitonic order is suppressed, resulting in a disordered insulating state characterized by partial occupation of the two orbitals with nonzero Chern numbers. This state is distinct from a fully orbital-polarized configuration. Furthermore, our analysis of an excitonic supersolid phase, in which excitonic and orbital orders coexist, demonstrates that orbital order remains robust under magnetic fields, while excitonic condensation is suppressed. These findings provide insights into the interplay between orbital motion and magnetic fields in multi-orbital correlated electron systems.
Strongly Correlated Electrons (cond-mat.str-el)
11 pages, 8 figures
Irreversible swap algorithms for soft sphere glasses
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-01-20 20:00 EST
Yoshihiko Nishikawa, Federico Ghimenti, Ludovic Berthier, Frédéric van Wijland
We extend to soft repulsive interaction potentials a recently proposed irreversible swap algorithm originally designed for polydisperse hard spheres. The original algorithm performs rejection-free, irreversible, collective swap moves. We show that event-driven cluster updates of particle diameters can also be performed in continuous potentials by introducing a factorised Metropolis probability. However, the Metropolis factorisation needed to deal with continuous potentials decreases the efficiency of the algorithm and mitigates the benefits of breaking detailed balance. This leads us to propose another irreversible swap algorithm using the standard Metropolis probability that accelerates the relaxation of soft sphere glasses at low temperatures, compared to the original swap algorithm. We apply these efficient swap algorithms to produce very stable inherent structures with vibrational density of states lacking the quasi-localised excitations observed in conventional glasses.
Soft Condensed Matter (cond-mat.soft), Disordered Systems and Neural Networks (cond-mat.dis-nn), Statistical Mechanics (cond-mat.stat-mech)
11 pages, 6 figures
Simultaneous achievement of large anomalous Nernst effect and reduced thermal conductivity in sintered polycrystalline topological Heusler ferromagnets
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-01-20 20:00 EST
Koichi Oyanagi, Hossein Sepehri-Amin, Kenta Takamori, Terumasa Tadano, Takumi Imamura, Ren Nagasawa, Krishnan Mahalingam, Takamasa Hirai, Fuyuki Ando, Yuya Sakuraba, Satoru Kobayashi, Ken-ichi Uchida
This study reports the observation of the large anomalous Nernst effect in polycrystalline ferromagnetic Co$_{2}$MnGa (CMG) slabs prepared by a spark plasma sintering method. By optimizing the sintering conditions, the anomalous Nernst coefficient reaches ~7.5 $\mu$V K$^{-1}$ at room temperature, comparable to the highest value reported in the single-crystalline CMG slabs. Owing to the sizable anomalous Nernst coefficient and reduced thermal conductivity, the dimensionless figure of merit in our optimized CMG slab shows the record-high value of ~8$\times$10$^{-4}$ at room temperature. With the aid of the nano/microstructure characterization and first-principles phonon calculation, this study discusses the dependence of the transport properties on the degree of crystalline ordering and morphology of crystal-domain boundaries in the sintered CMG slabs. The results reveal a potential of polycrystalline topological materials for transverse thermoelectric applications, enabling the construction of large-scale modules.
Materials Science (cond-mat.mtrl-sci), Applied Physics (physics.app-ph)
19 pages, 5 figures
Mapping the three-dimensional fermiology of the triangular lattice magnet EuAg$_4$Sb$_2$
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-01-20 20:00 EST
J. Green, Harry W. T. Morgan, Morgaine Mandigo-Stoba, William T. Laderer, Kuan-Yu Wey, Asari G. Prado, Chris Jozwiak, Aaron Bostwick, Eli Rotenberg, Christopher Gutiérrez, Anastassia N. Alexandrova, Ni Ni
In this paper, we report the temperature-field phase diagram as well as present a comprehensive study of the electronic structure and three-dimensional fermiology of the triangular-lattice magnet EuAg$_4$Sb$_2$, utilizing quantum oscillation measurements, angle-resolved photoemission spectroscopy and first-principles calculations. The complex magnetic phase diagram of EuAg$_4$Sb$_2$ highlights many transitions through nontrivial AFM states. Shubnikov-de Haas and de Haas-van Alphen oscillations were observed in the polarized ferromagnetic state of EuAg$_4$Sb$_2$, revealing three pairs of distinct spin-split frequency branches with small effective masses. A comparison of the angle-dependent oscillation data with first-principles calculations in the ferromagnetic state and angle-resolved photoemission spectra shows good agreement, identifying tubular hole pockets and hourglass-shaped hole pockets at the Brillouin zone center, as well as diamond-shaped electron pockets at the zone boundary. As the temperature increases, the frequency branches of the tiny hourglass pockets evolve into a more cylindrical shape, while the larger pockets remain unchanged. This highlights that variations in exchange splitting, driven by changes in the magnetic moment, primarily impact the small Fermi pockets without significantly altering the overall band structure. This is consistent with first-principles calculations, which show minimal changes near the Fermi level across ferromagnetic and simple antiferromagnetic states or under varying on-site Coulomb repulsion.
Materials Science (cond-mat.mtrl-sci), Strongly Correlated Electrons (cond-mat.str-el)
10 pages, 5 figures
In-plane anisotropy of charge density wave fluctuations in 1$T$-TiSe$_2$
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-01-20 20:00 EST
Xuefei Guo, Anshul Kogar, Jans Henke, Felix Flicker, Fernando de Juan, Stella X.-L. Sun, Issam Khayr, Yingying Peng, Sangjun Lee, Matthew J. Krogstad, Stephan Rosenkranz, Raymond Osborn, Jacob P. C. Ruff, David B. Lioi, Goran Karapetrov, Daniel J. Campbell, Johnpierre Paglione, Jasper van Wezel, Tai C. Chiang, Peter Abbamonte
We report measurements of anisotropic triple-$q$ charge density wave (CDW) fluctuations in the transition metal dichalcogenide 1$T$-TiSe$2$ over a large volume of reciprocal space with X-ray diffuse scattering. Above the transition temperature, $T{\text{CDW}}$, the out-of-plane diffuse scattering is characterized by rod-like structures which indicate that the CDW fluctuations in neighboring layers are largely decoupled. In addition, the in-plane diffuse scattering is marked by ellipses which reveal that the in-plane fluctuations are anisotropic. Our analysis of the diffuse scattering line shapes and orientations suggests that the three charge density wave components contain independent phase fluctuations. At $T_{\text{CDW}}$, long range coherence is established in both the in-plane and out-of-plane directions, consistent with the large observed value of the CDW gap compared to $T_{\text{CDW}}$, and the predicted presence of a hierarchy of energy scales.
Strongly Correlated Electrons (cond-mat.str-el), Materials Science (cond-mat.mtrl-sci)
Giant topological Hall effect in epitaxial Ni${80}$Fe${20}$/La${0.65}$Sr${0.35}$MnO$_3$ thin film heterostructures
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-01-20 20:00 EST
Kusampal Yadav, Dilruba Hasina, Nasiruddin Mondal, Sayantika Bhowal, Devajyoti Mukherjee
The emergence of new physical properties at the interfaces between complex oxides has always been of both fundamental and practical importance. Here, we report the observation of a giant topological Hall resistivity of $\sim 2.8 \mu \Omega$ \text{cm} at room temperature in an epitaxial thin-film heterostructure of permalloy (Py, Ni${80}$Fe${20}$) and the half-metallic ferromagnet La${0.65}$Sr${0.35}$MnO$_3$ (LSMO). This large magnitude of the topological Hall effect in the Py/LSMO heterostructure, compared to a single-layer Py thin film, is attributed to the optimized combination of ferromagnetism in LSMO and the strong spin-orbit-coupling-driven Rashba interaction at the interface. The introduction of a ferroelectric BaTiO$_3$ (BTO) sandwich layer in the Py/LSMO heterostructure also leads to an enhanced topological Hall resistivity compared to the single-layer Py thin film. Interestingly, magnetic force microscopy measurements reveal skyrmion-like features, suggesting the origin of the topological Hall effect. Our theoretical model calculations for the skyrmion lattice further indicate that the Rashba interaction, driven by the broken inversion symmetry in the Py/LSMO films, can account for the observed changes in the topological Hall effect at the interface. Our work opens the door for the potential use of Py/LSMO thin films in spintronic applications.
Materials Science (cond-mat.mtrl-sci)
17 pages, 10 figures
Room-Temperature Quantum Anomalous Hall Effect in Terbium monohalide
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-01-20 20:00 EST
Jianqi Zhong, Jianzhou Zhao, Jinyu Zou, Gang Xu
Following the successful experimental realization of the long-sought Quantum anomalous Hall (QAH) effect in thin films of chromium-doped (Bi,Sb)$_2$Te$_3$, enhancing the work temperature of QAH effect has emerged as a significant and challenging task in condensed matter physics. In this work, we demonstrate monolayer TbCl as a promising candidate to realize the room temperature QAH effect. Based on density functional theory + HSE hybrid functional, we identify the topological properties with Hall conductivity $G = -e^2/h$ per layer in three-dimensional ferromagnetic insulator TbCl, which is weakly staked by the QAH layers. The monolayer TbCl inherits the magnetic and topological properties, and exhibits the QAH effect corresponding to the Chern number $C=-1$. The topological band gap is significantly large and reaches 42.8 meV, which is beyond room temperatue. Meanwhile, the magnetic study finds that the extended $5d$ electrons contribute to the magnetic momentum of Tb and lead to sizable exchange and superexchange interactions, resulting in a high Curie temperature $T_c \sim 457$K. All these features demonstrate that monolayer TbCl will provide an ideal platform to realize the room temperature QAH effect.
Materials Science (cond-mat.mtrl-sci), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
6 pages, 4 figures
Out-of-equilibrium critical dynamics of the three-dimensional ${\mathbb Z}_2$ gauge model along critical relaxational flows
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-01-20 20:00 EST
Claudio Bonati, Haralambos Panagopoulos, Ettore Vicari
We address the out-of-equilibrium critical dynamics of the three-dimensional lattice ${\mathbb Z}_2$ gauge model, and in particular the critical relaxational flows arising from instantaneous quenches to the critical point, driven by purely relaxational (single-spin-flip Metropolis) upgradings of the link ${\mathbb Z}_2$ gauge variables. We monitor the critical relaxational dynamics by computing the energy density, which is the simplest local gauge-invariant quantity that can be measured in a lattice gauge theory. The critical relaxational flow of the three-dimensional lattice ${\mathbb Z}_2$ gauge model is analyzed within an out-of-equilibrium finite-size scaling framework, which allows us to compute the dynamic critical exponent $z$ associated with the purely relaxational dynamics of the three-dimensional ${\mathbb Z}_2$ gauge universality class. We obtain $z=2.610(15)$, which significantly improves earlier results obtained by other methods, in particular those obtained by analyzing the equilibrium critical dynamics.
Statistical Mechanics (cond-mat.stat-mech), High Energy Physics - Lattice (hep-lat)
11 pages
Two-dimensional ferroelectric crystal with temperature-invariant ultralow thermal conductivity
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-01-20 20:00 EST
We report the discovery of temperature-invariant ultralow thermal conductivity ($\kappa$) in monolayer \bpinse, a two-dimensional ferroelectric crystal with in-plane polarization. Using a combination of generalized Wigner transport equation theory and machine-learning-assisted molecular dynamics simulations, we reveal that the balance between particle-like phonon propagating and wave-like tunneling transport mechanisms results in a propagating-tunneling-invariant (PTI) ultralow thermal conductivity of approximately 0.6 W/mK (comparable to that of glass) over a broad temperature range ($150<T<800$K). This behavior stems from intrinsic strong lattice anharmonicity driven by ferroelectric dipolar fluctuations, eliminating the need for extrinsic structural modifications. In contrast, the \ainsemonolayer, which shares the same stoichiometry, exhibits a conventional temperature-dependent thermal conductivity, $\kappa (T) \propto T^{-1}$, typical of simple crystals. Furthermore, we demonstrate that the anharmonicity in \bpinse~can be precisely modulated by an external electric field, enabling on-demand control of thermal transport properties, including modifying the temperature scaling behavior of heat conductivity and achieving a large thermal switching ratio of $\approx$2.5. These findings provide fundamental insights into the interplay between field-tunable lattice anharmonicity, phonon dynamics, and thermal transport mechanisms.
Materials Science (cond-mat.mtrl-sci)
Triangular and dice quasicrystals modulated by generic 1D aperiodic sequences
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-01-20 20:00 EST
Toranosuke Matsubara, Akihisa Koga, Tomonari Dotera
We present a method for generating hexagonal aperiodic tilings that are topologically equivalent to the triangular and dice lattices. This approach incorporates aperiodic sequences into the spacing between three sets of grids for the triangular lattice, resulting in “modulated triangular lattices”. Subsequently, by replacing the triangles with rhombuses, parallelograms, or hexagons, modulated dice or honeycomb lattices are constructed. Using generalized Fibonacci, Thue-Morse, and tribonacci sequences, we demonstrate several examples of hexagonal aperiodic tilings. Structural analysis confirms that their diffraction patterns reflect the properties of the one-dimensional aperiodic sequences, namely pure point (Bragg peaks) or singular continuous. Our method establishes a general framework for constructing a broad range of hexagonal aperiodic systems, advancing aperiodic-crystal research into higher dimensions that were previously focused on one-dimensional aperiodic sequences.
Materials Science (cond-mat.mtrl-sci)
13 pages, 19 figures
Hall Coefficient of the Intercalated Graphite CaC$_6$ in the Uniaxial CDW Ground State
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-01-20 20:00 EST
Petra Đurkas Grozić, Barbara Keran, Anatoly M. Kadigrobov, Zoran Rukelj, Ivan Kupčić, Danko Radić
We evaluate the Hall coefficient characterising magnetotransport in an intercalated graphite CaC$_6$ with the Fermi surface reconstructed by an uniaxial charge density wave from closed pockets to open sheets. As the typical order parameter, corresponding to the pseudo-gap in electronic spectrum and consequently to spacing between electron trajectories in reciprocal space, is of the order of $10^2$K, magnetic breakdown in strong experimentally achievable fields of the order of 10T is inevitable. The classical expressions for the components of the magnetoconductivity tensor are strongly modified by magnetic field-assisted over-gap tunneling causing quantum interference. Due to magnetic breakdown, all magnetoconductivity components undergo strong quantum oscillations reflected in the Hall coefficient. In their nature, these are different than standard Shubnikov de Haas oscillations which would not appear in a system with an open Fermi surface.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
9 pages, 3 figures
Transformations in Perovskite Photovoltaics: Film Formation, Processing Conditions, and Recovery Outlook
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-01-20 20:00 EST
Bidisha Nath, Jeykishan Kumar, Sushant K Behera, Praveen C Ramamurthy, Debiprosad Roy Mahapatra, Gopalkrishna Hegde
Organometallic halide perovskites have garnered considerable attention in recent times due to their promising optoelectronic attributes, particularly within the realm of solar photovoltaics (PV). How perovskite films form is of utmost significance in shaping their structural and functional characteristics. In this context, the application of methylamine vapour during the precursor deposition and subsequent treatment during the film formation stages emerges as crucial for the development of high-quality perovskite films for solar cell applications. The utilization of methylamine vapour annealing is pivotal in improving the crystallinity, morphology, and overall integrity of perovskite films. This work investigates the characteristics of perovskite films based on methylamine lead iodide, focusing on aspects such as crystallographic structure and vibrational modes, which are directly linked to the performance of the devices. The maximum power conversion efficiencies (PCE) obtained are 19.5% and 18.6% using 1-step and 2-step processes are obtained. The effect of factors like trap states, film homogeneity, and interfaces on the device performance are explored through capacitance measurements, photoluminescence, and electroluminescence behaviour. The recombination behaviour of the perovskite films is correlated with the crystallographic properties. These findings provide valuable insights into the influence of different processing techniques, such as methylamine vapour treatment and vacuum annealing, on rejuvenating perovskite solar cells.
Materials Science (cond-mat.mtrl-sci)
Phase and sulfur vacancy engineering in cadmium sulfide for boosting hydrogen production from catalytic plastic waste photoconversion
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-01-20 20:00 EST
Thanh Tam Nguyen, Jacqueline Hidalgo-Jiménez, Xavier Sauvage (GPM), Katsuhiko Saito, Qixin Guo, Kaveh Edalati (WPI-I2CNER)
Cadmium sulfide (CdS) is a well-known low-bandgap photocatalyst, but its efficiency is often hindered by rapid photo-generated carrier recombination and a limited number of active catalytic sites. To overcome these challenges, this study introduces an efficient CdS photocatalyst through a novel strategy combining metastable-to-stable phase transformation and sulfur vacancy generation. This strategy integrates hydrothermal treatment and a high-pressure process to create sulfur vacancies, which serve as active catalytic sites, within a thermodynamically stable wurtzite (hexagonal) phase known for its superior photocatalytic properties. The resulting CdS photocatalyst demonstrates exceptional performance in photoreforming for hydrogen production and the conversion of polyethylene terephthalate (PET) plastic into valuable materials. Compared to commercial CdS catalysts, this new material shows a 23-fold increase in both hydrogen production and plastic degradation without the need for co-catalysts. Quenching experiments reveal that holes and hydroxyl radicals play crucial roles in the photoreforming process of this vacancy-rich CdS. First-principles calculations via density functional theory (DFT) indicate that the hexagonal phase possesses a lower bandgap and it exhibits further bandgap narrowing with the introduction of sulfur vacancies. These findings not only present an innovative approach to CdS processing but also highlight the critical role of sulfur vacancies as effective defects for the catalytic photoreforming of microplastics.
Materials Science (cond-mat.mtrl-sci), Chemical Physics (physics.chem-ph)
Chemical Engineering Journal, 2025, 504, pp.158730
Experimental realization of the ground state for the antiferromagnetic Ising model on a triangular lattice
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-01-20 20:00 EST
Ke Wang, Xing-Jian Liu, Li-Ming Tu, Jia-Jie Zhang, Vladimir N. Gladilin, Jun-Yi Ge
The antiferromagnetic Ising model on a triangular lattice (AFIT) exemplifies the most classical frustration system, arising from its triangular geometry that prevents all interactions from being simultaneously satisfied. Understanding geometric frustration in AFIT is crucial for advancing our knowledge of materials science and complex phases of matter. Here, we present a simple platform to study AFIT by arranging cylindrical magnets in vertical cavities of a triangular lattice, where magnets can slide along the cavity axis and stabilize either at the bottom or at the top of the cavity, analogous to the bistability of the Ising spin. The strong interactions of the magnets and the unique growing process allow the frustrated behavior and its ground state configurations to be directly observed. Notably, we observe a curved stripe phase, which is exotic to the Ising model. An effective thermalization process is developed to minimize the interaction energy, facilitating the evolution of various magnetic states, thereby visually realizing the ground state antiferromagnetic Ising model. Theoretical simulations and machine learning are performed concurrently to reveal the ground state and its evolution under effective thermal fluctuations, which are remarkably consistent with experimental results. Our system provides a unique platform to study frustrated systems and pave the way for future explorations in complex geometries.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Materials Science (cond-mat.mtrl-sci)
4 figures
Thermodynamic properties of fcc lead: A scalar and fully relativistic first principle study
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-01-20 20:00 EST
Balaram Thakur, Xuejun Gong, Andrea Dal Corso
This study investigates the thermodynamic properties of face-centered cubic lead (fcc-Pb) using ab-initio methods within the quasi-harmonic approximation (QHA), examining the influence of spin-orbit coupling (SOC) and the exchange-correlation functionals. Two types of ultrasoft pseudopotential (US-PP) are considered: one that excludes (scalar relativistic PP) and one that includes the SOC effects (fully relativistic PP). Further, for each PP, we test the performance of three popular exchange-correlation functionals: Perdew-Burke-Ernzerhof generalized gradient approximation (PBE) (Perdew et al. Phys. Rev. Lett. 77, 3865 (1996)), PBE modified for dense solids (PBEsol) (Perdew et al. Phys. Rev. Lett. 100, 136406 (2008)), and local density approximation (LDA) (Perdew et al. Phys. Rev. B 23, 5048 (1981)). We calculate the Helmholtz free energy, incorporating lattice vibrations (phonons) and electronic excitation contributions. The estimated equation of state (at 4 K and 301 K), phonon dispersions (at 100 K and 300 K), mode-Grüneisen parameters ({\gamma}q{\eta}) (at 100 K), volume thermal expansion coefficient (\b{eta}), isobaric heat capacity (CP), bulk modulus (BS), and thermodynamic average Grüneisen parameter ({\gamma}) are compared with the available experimental and theoretical studies. Moreover, the 0 K pressure-dependent elastic constant-coefficient (Cij) of fcc lead and Pugh ratio, Debye temperature, and longitudinal and transverse sound velocities for polycrystalline lead are presented. The contributions of electronic excitations in all the thermodynamic properties are found to be negligible. With increasing pressure, the role of spin-orbit effects decreases but does not vanish. Our findings demonstrate that SOC leads to results distinct from the SR approach, but agreement with the experiment is not consistently improved by including SOC.
Materials Science (cond-mat.mtrl-sci)
Computational Materials Science 249, 113677 (2025)
Emergent scales and spatial correlations at the yielding transition of glassy materials
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-01-20 20:00 EST
Stefano Aime, Domenico Truzzolillo
Glassy materials yield under large external mechanical solicitations. Under oscillatory shear, yielding shows a well-known rheological fingerprint, common to samples with widely different microstructures. At the microscale, this corresponds to a transition between slow, solid-like dynamics and faster liquid-like dynamics, which can coexist at yielding in a finite range of strain amplitudes. Here, we capture this phenomenology in a lattice model with two main parameters: glassiness and disorder, describing the average coupling between adjacent lattice sites, and their variance, respectively. In absence of disorder, our model yields a law of correspondent states equivalent to trajectories on a cusp catastrophe manifold, a well-known class of problems including equilibrium liquid-vapour phase transitions. Introducing a finite disorder in our model entails a qualitative change, to a continuous and rounded transition, whose extent is controlled by the magnitude of the disorder. We show that a spatial correlation length $\xi$ emerges spontaneously from the coupling between disorder and bifurcating dynamics. With vanishing disorder, $\xi$ diverges and yielding becomes discontinuous, suggesting that the abruptness of yielding can be rationalized in terms of a lengthscale of dynamic heterogeneities.
Soft Condensed Matter (cond-mat.soft), Disordered Systems and Neural Networks (cond-mat.dis-nn), Materials Science (cond-mat.mtrl-sci)
24 pages, 6 figures
Symmetry-adapted closest Wannier modeling based on complete multipole basis set
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-01-20 20:00 EST
Rikuto Oiwa, Akane Inda, Satoru Hayami, Takuya Nomoto, Ryotaro Arita, Hiroaki Kusunose
We have developed a method to construct a symmetry-adapted Wannier tight-binding model based on the closest Wannier formalism and the symmetry-adapted multipole theory. Since the symmetry properties of the closest Wannier functions are common to those of the original atomic orbitals, symmetry-adapted multipole basis (SAMB) can be defined as the complete orthonormal matrix basis set in the Hilbert space of the closest Wannier functions. Utilizing the completeness and orthonormality of SAMBs, the closest Wannier Hamiltonian can be expressed as a linear combination of SAMBs belonging to the identity irreducible representation, thereby fully restoring the symmetry of the system. Moreover, the linear coefficients of each SAMB (model parameters) related to crystalline electric fields, spin-orbit coupling, and electron hoppings are determined through simple matrix projection without any iterative procedure. Thus, this method allows us to unveil mutual interplay among hidden electronic multipole degrees of freedom in the Hamiltonian and numerically evaluate them. We demonstrate the effectiveness of our method by modeling monolayer graphene under a perpendicular electric field, highlighting its utility in symmetrizing the closest Wannier model, quantifying symmetry breaking, and predicting unusual responses. The method is implemented in the open-source Python library SymClosestWannier, with the codes available on GitHub (this https URL).
Materials Science (cond-mat.mtrl-sci), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
20 pages, 9 figures
Optical probes of two-component pairing states in transition metal dichalcogenides
New Submission | Superconductivity (cond-mat.supr-con) | 2025-01-20 20:00 EST
Miguel-Ángel Sánchez-Martínez, Daniel Muñoz-Segovia, Fernando de Juan
Certain transition metal dichalcogenide heterostructures based on 2H-NbSe$_2$ and 4H$_b$-TaS$_2$ have recently displayed surprising signatures of unconventional superconductivity. While the pairing channel remains unknown, it has been argued that spin fluctuations should lead to a two-component $E’$ pairing state which is compatible with some experimental features. Exploiting the particular multi-orbital character of the Fermi surface and the presence of Ising spin-orbit coupling which enable finite optical conductivity in the clean limit, in this work we predict clear-cut optical signatures of the chiral and nematic ground states of the $E’$ pairing. In particular, we show how the spontaneous breaking of time-reversal and threefold symmetry are reflected in the optical Hall and anisotropic conductivities, respectively, while different spectral features can be connected with the momentum dependence of the gap functions. Our work provides a fingerprint that can be measured experimentally, constraining the pairing channel in TMD superconductors, and will help determine whether superconductivity is topological in these systems.
Superconductivity (cond-mat.supr-con)
7 pages, 5 figures
Butterfly Patterns for Stretched Inhomogeneous Gel Networks using Large-Scale Molecular Dynamics Simulations
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-01-20 20:00 EST
Katsumi Hagita, Takahiro Murashima
Large-scale coarse-grained molecular dynamics simulations of inhomogeneous gel networks were performed to investigate abnormal butterfly patterns in two-dimensional scattering. The networks were diamond lattice-based with distributions in the number of beads between the crosslink points. Remarkably, the results confirm that the abnormal butterfly pattern orig-inates from stronger inhomogeneity. For the examined systems, the range of scattering wavevector q for the normal butterfly pattern was markedly different from those for the abnormal butterfly patterns. The findings address an essential aspect of the discrepancy between theorical prediction and experimental observations.
Soft Condensed Matter (cond-mat.soft), Computational Physics (physics.comp-ph)
Topological-to-Topological Transition Induced by On-Site Nonlinearity in a One-Dimensional Topological Insulator
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-01-20 20:00 EST
Kazuki Sone, Yasuhiro Hatsugai
Recent studies have extended the notion of band topology to nonlinear systems by defining nonlinear counterparts of eigenvalue problems. They have found the nonlinearity-induced topological transition, while it has required complicated nonlinearity such as off-diagonal one. Thus, the existence of nonlinearity-induced transitions has been unclear under homogeneous on-site nonlinearity, which is ubiquitously found in nature. We here reveal that such on-site nonlinearity can induce transitions of topological modes, where topological modes converging to zero begin to converge to nonzero values. Since such nonlinearity-induced transition remains the bulk band topology unchanged, we can regard it as a transition from a conventional topological mode to one unique to nonlinear systems. We analyze a nonlinear eigenvalue problem by rewriting it to a dynamical system in the spatial direction and clarify that the nonlinearity-induced transition is a result of the bifurcation in the spatial dynamics. We also propose a possible setup to observe the nonlinearity-induced transition that uses a gradual amplification of nonlinear waves. These results provide a general designing principle of topological insulators controlled by nonlinearity.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Statistical Mechanics (cond-mat.stat-mech), Optics (physics.optics)
6+5 pages, 4+3 figures
Transport characterization and quantum dot coupling in commercial 22FDX
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-01-20 20:00 EST
Giselle A. Elbaz, Pierre-Louis Julliard, Mikaël Cassé, Heimanu Niebojewski, Benoit Bertrand, Grégoire Roussely, Valentin Labracherie, Maud Vinet, Tristan Meunier, Bruna Cardoso Paz
Different groups worldwide have been working with the GlobalFoundries 22nm platform (22FDX) with the hopes of industrializing the fabrication of Si spin qubits. To guide this effort, we have performed a systematic study of six of the foundry’s processes of reference (POR). Using effective mobility as a figure of merit, we study the impact of gate stack, channel type and back bias as a function of temperature. This screening process selected qubit devices that allowed us to couple quantum dots along both the length and width of the Si channel. We present stability diagrams with clear and regular honeycomb patterns, where spurious elements such as dopants are not observed. By combining these results with room and low temperature simulations, we provide insights into potential technology optimizations and show both the utility of qubit pre-screening protocols as well as the advantages of leveraging forward body bias within an FDSOI (Fully Depleted Silicon-On-Insulator) qubit platform.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Quantum Physics (quant-ph)
7 pages, 12 figures + 2 tables
Simultaneous mapping of the ultrafast time and fluence dependence of the laser-induced insulator-to-metal transition in magnetite
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-01-20 20:00 EST
J.O. Schunck, P.S. Miedema, R.Y. Engel, S. Dziarzhytski, G. Brenner, N. Ekanayake, C.-F. Chang, P. Bougiatioti, F. Döring, B. Rösner, C. David, C. Schüßler-Langeheine, M. Beye
Pump-probe methods are a ubiquitous tool in the field of ultrafast dynamic measurements. In recent years, X-ray free-electron laser experiments have gained importance due to their ability to probe with high chemical selectivity and at atomic length scales. To obtain the complete dynamic information, measurements are typically repeated many thousands of times with varying delay and/or fluence settings. This generally necessitates that the sample fully recovers before the subsequent excitation and that probe pulses and the induced dynamic evolution are comparable to each other. These conditions present a significant challenge when the sample fluctuates between different initial states or when it is susceptible to damage. Also, source fluctuations are normally intrinsic to free-electron laser pulses. Here, we present a time-to-space mapping imaging scheme that enables us to record a delay range of several picoseconds as well as a laser fluence range of about one order of magnitude in every single shot of the x-ray probe. This approach can circumvent the aforementioned preconditions. We demonstrate the use of this scheme by mapping the femto- and picosecond dynamics of the optically induced insulator-to-metal Verwey transition in a magnetite thin film. We employ resonant diffraction at the free-electron laser FLASH for probing. The dynamics of the magnetite thin film are found to follow a biexponential decay in line with earlier studies on bulk crystals. By extrapolating our results towards the conditions found at X-ray free-electron lasers with higher energy, we demonstrate that the presented data could be recorded in a single shot.
Materials Science (cond-mat.mtrl-sci), Strongly Correlated Electrons (cond-mat.str-el)
The following article has been submitted to Structural Dynamics. After it is published, it will be found at this https URL
First-principles study of electronic and magnetic properties of self-intercalated van der Waals magnet Cr$_3$Ge$_2$Te$_6$
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-01-20 20:00 EST
Jia-wan Li, Shi-Bo Zhao, Lin Zhuang, Yusheng Hou
Self-intercalated van der Waals magnets, characterized by self-intercalating native atoms into van der Waals layered structures with intrinsic magnetism, exhibit a variety of novel physical properties. Here, using first-principles calculations and Monte Carlo simulations, we report a self-intercalated van der Waals ferromagnet, Cr$_3$Ge$_2$Te$_6$, which has a high Curie temperature of 492 K. We find that Cr$_3$Ge$_2$Te$_6$ is nearly half-metallic with a spin polarization reaching up to 90.9%. Due to the ferromagnetism and strong spin-orbit coupling effect in Cr$_3$Ge$_2$Te$_6$, a large anomalous Hall conductivity of 138 $\Omega^{-1}$ cm$^{-1}$ and 305 $\Omega^{-1}$ cm$^{-1}$ can be realized when its magnetization is along its magnetic easy axis and hard axis, respectively. By doping electrons (holes) into Cr$_3$Ge$_2$Te$_6$, these anomalous Hall conductivities can be increased up to 318 $\Omega^{-1}$ cm$^{-1}$ (648 $\Omega^{-1}$ cm$^{-1}$). Interestingly, a 5-layer Cr$_3$Ge$_2$Te$_6$ thin film retains the room-temperature ferromagnetism with a higher spin polarization and larger anomalous Hall conductivity. Our work demonstrates that Cr$_3$Ge$_2$Te$_6$ is a novel room-temperature self-intercalated ferromagnet with high spin polarization and large anomalous Hall conductivity, offering great opportunities for designing nano-scale electronic devices.
Materials Science (cond-mat.mtrl-sci), Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Applied Physics (physics.app-ph)
16 pages, 6 figures, accepted by Chinese Physics B
Three-dimensional deformations in single-layer $\alpha$ antimonene and interaction with a Au(111) surface from first principles
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-01-20 20:00 EST
José de Jesús Villalobos Castro, Thomas Pierron, Stephane Pons, Johann Coraux, Lorenzo Sponza, Sergio Vlaic
Using density functional theory, we investigate the electronic structure of the alpha phase of an antimony monolayer in its isolated form and in contact to the (111) surface of gold. We demonstrate that the isolated single-layer actually displays a slightly modulated puckering that stabilizes the monolayer, not a uniform one as often assumed. Moreover, it has dramatic consequences on the electronic band structure: the material is a semiconductor with low-dispersing bands near the Brillouin zone center. By further application of about 12% strain on the armchair direction, a double-cone features develops wherein an electronic bandgap of about 21~meV is found. When in contact with a Au(111) surface, a strong interaction with gold arises, as it appears clearly from (i) substantial atomic displacements compared to the isolated form, and (ii) hybridization of Sb and Au orbitals. The latter profoundly modifies the electronic band structure by strengthening the spin-orbit splitting of hybridized bands and spoiling the double-cone feature whose manipulation through substrate-induced strain appears therefore questionable, at least in the simulated epitaxial implementation.
Materials Science (cond-mat.mtrl-sci)
7 pages, 5 figures
Dynamical response of noncollinear spin systems at constrained magnetic moments
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-01-20 20:00 EST
Miquel Royo, Massimiliano Stengel
Noncollinear magnets are notoriously difficult to describe within first-principles approaches based on density-functional theory (DFT) because of the presence of low-lying spin excitations. At the level of ground-state calculations, several methods exist to constrain the magnetic moments to a predetermined configuration, and thereby accelerate convergence towards self-consistency. Their use in a perturbative context, however, remains very limited. Here we present a general methodological framework to achieve parametric control over the local spin moments at the linear-response level. Our strategy builds on the concept of Legendre transform to switch between various flavors of magnetic functionals, and to relate their second derivatives via simple linear-algebra operations. Thereby, we can address an arbitrary response function at the time-dependent DFT level of theory with optimal accuracy and minimal computational effort. In the low frequency limit, we identify the leading correction to the existing adiabatic formulation of the problem [S. Ren \emph{et al.}, Phys. Rev. X {\bf 14}, 011041 (2024)], consisting in a renormalization of the phonon and magnon masses due to electron inertia. As a demonstration, we apply our methodology to the study of the THz optical response in bulk CrI$_3$, where we identify a hybrid electromagnon with mixed spin-lattice character.
Materials Science (cond-mat.mtrl-sci), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Exploring Unique Characteristics in Stark Many-Body Localization
New Submission | Disordered Systems and Neural Networks (cond-mat.dis-nn) | 2025-01-20 20:00 EST
Stark Many-Body Localization (MBL) is a phenomenon observed in quantum systems in the absence of disorder, where the presence of a linear potential, known as the Stark field, causes the localization. Our study aims to provide novel insight into the properties of Stark MBL and to discover unique entanglement characteristics specific to this phenomenon. The phase diagram analysis reveals different behavior with varying interaction strengths. Furthermore, we highlight the influence of domain wall structures on the breakdown of the entanglement entropy of the system. Moreover, the investigation of Out-of-Time-Ordered Correlator (OTOC) behavior demonstrates distinct responses to interactions based on domain wall configurations. Our findings contribute to a better understanding of Stark MBL and offer valuable insights into the entanglement properties of systems subjected to Stark potentials.
Disordered Systems and Neural Networks (cond-mat.dis-nn), Other Condensed Matter (cond-mat.other), Quantum Physics (quant-ph)
5 pages, 5 figures
Absence of orbital current torque in Ta/ferromagnet bilayers
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-01-20 20:00 EST
It has become a heated debate as to whether the orbital Hall effect of a material could generate a non-local orbital current and a non-zero spin-orbit torque on an adjacent magnetic layer. Here, we report unambiguous evidence that, regardless of the ferromagnets (FMs) (e.g., Ni, Ni81Fe19, Fe, Fe60Co20B20, and FePt), the spin-orbit torque generated by an adjacent Ta, which is predicted to have a 50 times greater positive orbital Hall conductivity than the negative spin Hall conductivity, has essentially the same, negative efficiency, in agreement with the spin Hall effect of Ta being the only source of the interfacial torque. We identify that the constant, positive estimate of the torque of the Ta/FM samples from spin-torque ferromagnetic resonance (ST-FMR) analysis in a specific FM thickness range (>2 nm for Ni), that was heavily cited in the literature to signify an orbital current torque but strongly disagrees with the fairly long relaxation length in other orbital current torque claims, results from the overlook of a significant thick-dependent self-induced ST-FMR signal of the FM. These results indicate the absence of orbital current torque in Ta/ferromagnet systems, regardless of the type, the SOC strength, and the layer thickness of the ferromagnets.
Materials Science (cond-mat.mtrl-sci)
Linear and Nonlinear Edelstein Effects in Chiral Topological Semimetals
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-01-20 20:00 EST
Recently, there has been growing interest in achieving on-demand control of magnetism through electrical and optical means. In this work, we provide first-principles predictions for the linear and nonlinear Edelstein effects (LEE and NLEE) in the chiral topological semimetal CoSi. The LEE and NLEE represent first- and second-order magnetic responses to external electric fields, enabling precise manipulation of magnetization via electrical and optical methods. We demonstrate that although both LEE and NLEE require time-reversal symmetry breaking, they can still be realized in non-magnetic materials, as time-reversal symmetry can be spontaneously broken by heat and dissipation, according to the second law of thermodynamics. Meanwhile, due to different inversion symmetry selection rules, the LEE and NLEE manifest opposite and identical signs in the two enantiomers of CoSi, respectively. We further quantify the magnitude of LEE and NLEE, showing that electrically or optically induced magnetization can reach 10 Bohr magneton per unit cell when the external electric field strength is comparable with the internal atomic electric field, which is on the order of 1 V/A. Our work offers a systematical approach for predicting the electrical and optical control of magnetism in real materials, paving the way for potential applications in areas such as spintronics and magnetic memories.
Materials Science (cond-mat.mtrl-sci)
14 pages, 3 figures
Materials Today Quantum 5, 100022 (2025)
Investigation of Polymer Association Behaviors in Solvents Using a Coarse-Grained Model
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-01-20 20:00 EST
The associative interaction, such as hydrogen bonding, can bring about versatile functionalities to polymer systems, which has been investigated by tremendous researches, but the fundamental understanding on association process is still lacking. In this study, a reaction-controlled association model is proposed to delve into the polymer association activities in solvents, which is proved to obey the principle of thermodynamics. Additionally, associative polymer chain configurational bias method is developed to improve sampling efficiency, demonstrating a significantly faster relaxation process. First, we set non-bonded interactions to be zero, and only keep the chain connectivity and association. It is found that the association process intrinsically follows Bernoulli process by comparing the simulation results and analytic results. Next, we include non-bonded interactions into the simulation to examine its effects. It emerged that the excluded volume effect and solvents immiscibility effects can result in inhomogeneous associating probability distribution along the chain contour, in contrast to the homogeneity observed in ideal systems, thereby shifting from the binomial distribution to Poisson binomial distribution. At last, the study is extended to cooperative association systems. The incorporation of cooperative association can lead to the coexistence of coil and globule state at the transition point, verified by the potential of mean force calculation. Finally, a mathematical model is proposed, illustrating the changes in statistical weight induced by sequence enthalpy bias, which is the consequence of cooperative behaviors.
Soft Condensed Matter (cond-mat.soft)
Beyond-Hubbard pairing in a cuprate ladder
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-01-20 20:00 EST
Hari Padma, Jinu Thomas, Sophia TenHuisen, Wei He, Ziqiang Guan, Jiemin Li, Byungjune Lee, Yu Wang, Seng Huat Lee, Zhiqiang Mao, Hoyoung Jang, Valentina Bisogni, Jonathan Pelliciari, Mark P. M. Dean, Steven Johnston, Matteo Mitrano
The Hubbard model is believed to capture the essential physics of cuprate superconductors. However, recent theoretical studies suggest that it fails to reproduce a robust and homogeneous superconducting ground state. Here, using resonant inelastic x-ray scattering and density matrix renormalization group calculations, we show that magnetic excitations in the prototypical cuprate ladder Sr${14}$Cu${24}$O$_{41}$ are inconsistent with those of a simple Hubbard model. The magnetic response of hole carriers, contributing to an emergent branch of spin excitations, is strongly suppressed. This effect is the consequence of d-wave-like pairing, enhanced by nearly an order of magnitude through a large nearest-neighbor attractive interaction. The similarity between cuprate ladders and the two-dimensional compounds suggests that such an enhanced hole pairing may be a universal feature of superconducting cuprates.
Strongly Correlated Electrons (cond-mat.str-el), Materials Science (cond-mat.mtrl-sci), Superconductivity (cond-mat.supr-con)
Main + SM: 21 pages, 13 figures
Intense Laser-Driven Phenomena In Weyl Semimetals
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-01-20 20:00 EST
Condensed-matter provides attractive platforms to realize exotic particles, originally proposed in high-energy physics. Weyl semimetal (WSM) is a material in which low-energy collective excitations are governed by massless Weyl fermions, which appear in pairs of opposite chirality and are topologically protected. Thus, the discovery of topological materials such as WSM has heralded a new era in contemporary physics. Moreover, these materials offer exciting opportunities in next-generation signal processing and optoelectronics. This thesis explores different facets of the intense laser-driven phenomena in WSM for applications in emerging lightwave-driven Petahertz electronics and quantum technologies.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Optics (physics.optics), Quantum Physics (quant-ph)
PhD thesis
Cooper-Pair Localization in the Magnetic Dynamics of a Cuprate Ladder
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-01-20 20:00 EST
A. Scheie, P. Laurell, J. Thomas, V. Sharma, A. I. Kolesnikov, G. E. Granroth, Q. Zhang, B. Lake, M. Mihalik Jr., R. I. Bewley, R. S. Eccleston, J. Akimitsu, E. Dagotto, C. D. Batista, G. Alvarez, S. Johnston, D. A. Tennant
We investigate the spin dynamics of the cuprate ladder Sr${2.5}$Ca${11.5}$Cu${24}$O${41}$ to elucidate the behavior of its intrinsically doped holes. Combining high-resolution neutron spectroscopy and density matrix renormalization group calculations enables a comprehensive analysis of the collective magnetic dynamics. We find a general absence of magnetic signatures from unpaired charges, indicating holes within the system form strongly bound localized Cooper pairs. A one-band Hubbard model fails to match the spectral features but a straightforward extension to a large attractive nearest-neighbor interaction quantitatively explains our results. Our finding shows the significance of additional interactions beyond the long-predicted quantum spin pairing in the ($d$-wave) charge pairing process. Considering the parallels between ladders and two-dimensional cuprates, these results are potentially relevant for square lattices as well.
Strongly Correlated Electrons (cond-mat.str-el), Superconductivity (cond-mat.supr-con)
Main text plus supplementary material
Static Born charges and quantum capacitance in metals and doped semiconductors
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-01-20 20:00 EST
Asier Zabalo, Cyrus E. Dreyer, Massimiliano Stengel
Born dynamical charges ($\textbf{Z}^\text{dyn}$) play a key role in the lattice dynamics of most crystals, including both insulators and metals in the nonadiabatic (“clean”) regime. Very recently, the so-called static Born charges, $\textbf{Z}^\text{stat}$, were introduced [G. Marchese, et al., Nat. Phys. $\mathbf{20}$, 88 (2024)] as a means to modeling the long-wavelength behavior of polar phonons in overdamped (“dirty”) metals. Here we present a method to calculate $\textbf{Z}^\text{stat}$ directly at the zone center, by applying the $2n+1$ theorem to the long-wavelength expansion of the charge response to a phonon. Furthermore, we relate $\textbf{Z}^\text{stat}$ to the charge response to a uniform strain perturbation via an exact sum rule, where the quantum capacitance of the material plays a crucial role. We showcase our findings via extensive numerical tests on simple metals aluminum and copper, polar metal LiOsO$_3$, and doped semiconductor SrTiO$_3$. Based on our results, we critically discuss the physical significance of $\textbf{Z}^\text{stat}$ in light of their dependence on the choice of the electrostatic reference, and on the length scale that is assumed in the definition of the macroscopic potentials.
Materials Science (cond-mat.mtrl-sci)
Magnetic properties of the zigzag ladder compound SrTb2O4
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-01-20 20:00 EST
F. Orlandi, M. Ciomaga Hatnean, D.A. Mayoh, J.P. Tidey, S.X.M. Riberolles, G. Balakrishnan, P. Manuel, D.D. Khalyavin, H.C. Walker, M.D. Le, B. Ouladdiaf, A. R. Wildes, N. Qureshi, O.A. Petrenko
We report on the properties of SrTb2O4, a frustrated zigzag ladder antiferromagnet, studied by single crystal neutron diffraction (with polarised neutrons in zero field and unpolarised neutrons in an applied magnetic field), as well as by neutron spectroscopy on a polycrystalline sample. The neutron scattering results are supported by single crystal magnetisation and heat capacity measurements. In zero field, neutron diffraction data show no transition to a magnetically ordered state down to the lowest experimentally available temperature of 35 mK, and the material remains magnetically disordered down to this temperature. Polarised neutron diffraction measurements reveal the presence of a diffuse scattering signal suggesting only very weak spin-spin correlations in the ground state. For H // c (the easy magnetisation direction), we followed the magnetisation process using neutron diffraction measurements and observed the appearance of field-induced magnetic Bragg peaks with integer h and k indices in the (hk0) scattering plane. No magnetic peaks with a non-zero propagation vector were detected. The observed in-field data fit well to a simple two-sublattice model with magnetic moments aligned along the field direction but being significantly different in magnitude for the two inequivalent Tb3+ sites in the unit cell. Overall, the collected data point to a nonmagnetic ground state in SrTb2O4 despite the presence of strong interactions.
Strongly Correlated Electrons (cond-mat.str-el)
13 pages, 11 figures
Hopper flows of dense suspensions: a 2D microfluidic model system
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-01-20 20:00 EST
Lars Kool, Jules Tampier, Philippe Bourrianne, Anke Lindner
Flows of particles through bottlenecks are ubiquitous in nature and industry, involving both dry granular materials and suspensions. However, practical limitations of conventional experimental setups hinder the full understanding of these flows in confined geometries. Here, we present a microfluidic setup to investigate experimentally the flow of dense suspensions in a two-dimensional hopper channel. Particles with controlled properties are in-situ fabricated with a photolithographic projection method and compacted at the channel constriction using a Quake valve. The setup is characterized by examining the flow of a dense suspension of hard, monodisperse disks through constrictions of varying widths. We demonstrate that the microfluidic hopper discharges particles at constant rate, resulting from the channel resistance being dominated by the presence of densely packed particles within the tapered section of the hopper. Under imposed flow rate the discharge remains independent of particle and orifice sizes, whereas it exhibits a Beverloo-like scaling under pressure-imposed conditions. Additionally, we show that the statistics of clog formation in our microfluidic hopper follow the same stochastic laws as reported in other systems. Finally, we show how the versatility of our microfluidic model system can be used to investigate the outflow and clogging of suspensions of more complex particles.
Soft Condensed Matter (cond-mat.soft), Fluid Dynamics (physics.flu-dyn)
From strong to weak correlations in breathing-mode kagome van der Waals materials: Nb$_3$(F,Cl,Br,I)$_8$ as a robust and versatile platform for many-body engineering
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-01-20 20:00 EST
Joost Aretz, Sergii Grytsiuk, Xiaojing Liu, Giovanna Feraco, Chrystalla Knekna, Muhammad Waseem, Zhiying Dan, Marco Bianchi, Philip Hofmann, Mazhar N. Ali, Mikhail I. Katsnelson, Antonija Grubišić-Čabo, Hugo U. R. Strand, Erik G. C. P. van Loon, Malte Rösner
By combining ab initio downfolding with cluster dynamical mean-field theory, we study the degree of correlations in the low-temperature structures of the breathing-mode kagome van der Waals materials Nb$_3$(F,Cl,Br,I)$_8$. We show that the Coulomb correlation strength steadily increases from I to Br, Cl, and F, allowing us to identify Nb$_3$I$_8$ as a weakly correlated (obstructed atomic) insulator whose gap is only mildly affected by the local Coulomb interaction. Nb$_3$Br$_8$ and Nb$_3$Cl$_8$ are strongly correlated insulators, whose gaps are significantly influenced by Coulomb-induced vertex corrections. Nb$_3$F$_8$ is a prototypical bulk Mott-insulator whose gap is initially opened by strong correlation effects. Angle-resolved photoemission spectroscopy measurements comparing Nb$_3$Br$_8$ and Nb$_3$I$_8$ allow us to experimentally confirm these findings by revealing spectroscopic footprints of the degree of correlation. Our calculations further predict that the entire material family can be tuned into correlated charge-transfer or Mott-insulating phases upon electron or hole doping. Our magnetic property analysis additionally shows that inter-layer magnetic frustrations in the high-temperature phase drive the lattice phase transition to the low-temperature structures. The accompanying bilayer hybridization through inter-layer dimerization yields magnetic singlet ground states in the Cl, Br, and I compounds. Our findings establish Nb$_3$X$_8$ as a robust, versatile, and tunable class for van der Waals-based Coulomb and Mott engineering and allow us to speculate on the symmetry-breaking effects necessary for the recently observed Josephson diode effect in NbSe$_2$/Nb$_3$Br$_8$/NbSe$_2$ heterostructures.
Strongly Correlated Electrons (cond-mat.str-el)
23 pages, 18 figures
Principled model selection for stochastic dynamics
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-01-20 20:00 EST
Andonis Gerardos, Pierre Ronceray
Complex dynamical systems, from macromolecules to ecosystems, are often modeled by stochastic differential equations (SDEs). To learn such models from data, a common approach involves decomposing the SDE into a linear combination of basis functions. However, this can induce overfitting due to the proliferation of parameters. To address this, we introduce Parsimonious Stochastic Inference (PASTIS), a principled method that removes superfluous parameters from SDE models by combining likelihood-estimation statistics with extreme value theory. We benchmark it against existing methods and show that it reliably selects the exact minimal models from large libraries of functions, even with a low sampling rate or measurement error. We show that it extends to stochastic partial differential equations and demonstrate applications to the inference of ecological networks and reaction-diffusion dynamics.
Soft Condensed Matter (cond-mat.soft), Statistical Mechanics (cond-mat.stat-mech), Data Analysis, Statistics and Probability (physics.data-an), Machine Learning (stat.ML)
Photonic chiral state transfer near the Liouvillian exceptional point
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-01-20 20:00 EST
Huixia Gao, Konghao Sun, Dengke Qu, Kunkun Wang, Lei Xiao, Wei Yi, Peng Xue
As branch-point singularities of non-Hermitian matrices, the exceptional points (EPs) exhibit unique spectral topology and criticality, with intriguing dynamic consequences in non-Hermitian settings. In open quantum systems, EPs also emerge in the Liouvillian spectrum, but their dynamic impact often pertains to the transient dynamics and is challenging to demonstrate. Here, using the flexible control afforded by single-photon interferometry, we study the chiral state transfer when the Liouvillian EP is parametrically encircled. Reconstructing the density-matrix evolution by experimentally simulating the quantum Langevin equation, we show that the chirality of the dynamics is only present within an intermediate encircling timescale and dictated by the landscape of the Liouvillian spectrum near the EP. However, the chirality disappears at long times as the system always relaxes to the steady state. We then demonstrate the universal scaling of the chirality with respect to the encircling time. Our experiment confirms the transient nature of chiral state transfer near a Liouvillian EP in open quantum systems, while our scheme paves the way for simulating general open-system dynamics using single photons.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Quantum Physics (quant-ph)
6 pages, 4 figures