CMP Journal 2025-01-14
Statistics
Physical Review Letters: 19
Physical Review X: 1
arXiv: 61
Physical Review Letters
Thermal Area Law in Long-Range Interacting Systems
Research article | Mathematical physics | 2025-01-14 05:00 EST
Donghoon Kim, Tomotaka Kuwahara, and Keiji Saito
The area law of the bipartite information measure characterizes one of the most fundamental aspects of quantum many-body physics. In thermal equilibrium, the area law for the mutual information universally holds at arbitrary temperatures as long as the systems have short-range interactions. In systems with power-law decaying interactions, ${r}^{- \alpha }$ ($r$: distance), conditions for the thermal area law are elusive. In this Letter, we aim to clarify the optimal condition $\alpha >{\alpha }{c}$ such that the thermal area law universally holds. A standard approach to considering the conditions is to focus on the magnitude of the boundary interaction between two subsystems. However, we find here that the thermal area law is more robust than this conventional argument suggests. We show the optimal threshold for the thermal area law by ${\alpha }{c}=(D+1)/2$ ($D$: the spatial dimension of the lattice), assuming a power-law decay of the clustering for the bipartite correlations. Remarkably, this condition encompasses even the thermodynamically unstable regimes $\alpha <D$. We verify this condition numerically, finding that it is qualitatively accurate for both integrable and nonintegrable systems. Unconditional proof of the thermal area law is possible by developing the power-law clustering theorem for $\alpha >D$ above a threshold temperature. Furthermore, the numerical calculation for the logarithmic negativity shows that the same criterion $\alpha >(D+1)/2$ applies to the thermal area law for quantum entanglement.
Phys. Rev. Lett. 134, 020402 (2025)
Mathematical physics, Quantum correlations in quantum information, Quantum entanglement, Quantum information theory, Quantum statistical mechanics, Lattice models in statistical physics, Quantum many-body systems, Many-body techniques, Mathematical physics methods
Quantized Axial Charge of Staggered Fermions and the Chiral Anomaly
Research article | Anomalies | 2025-01-14 05:00 EST
Arkya Chatterjee, Salvatore D. Pace, and Shu-Heng Shao
In the $1+1\mathrm{D}$ ultralocal lattice Hamiltonian for staggered fermions with a finite-dimensional Hilbert space, there are two conserved, integer-valued charges that flow in the continuum limit to the vector and axial charges of a massless Dirac fermion with a perturbative anomaly. Each of the two lattice charges generates an ordinary U(1) global symmetry that acts locally on operators and can be gauged individually. Interestingly, they do not commute on a finite lattice and generate the Onsager algebra, but their commutator goes to zero in the continuum limit. The chiral anomaly is matched by this non-Abelian algebra, which is consistent with the Nielsen-Ninomiya theorem. We further prove that the presence of these two conserved lattice charges forces the low-energy phase to be gapless, reminiscent of the consequence from perturbative anomalies of continuous global symmetries in continuum field theory. Upon bosonization, these two charges lead to two exact U(1) symmetries in the XX model that flow to the momentum and winding symmetries in the free boson conformal field theory.
Phys. Rev. Lett. 134, 021601 (2025)
Anomalies, Lattice field theory, Chiral symmetry
Distinguishing Dirac from Majorana Heavy Neutrino at Future Lepton Colliders
Research article | Extensions of fermion sector | 2025-01-14 05:00 EST
Qing-Hong Cao, Kun Cheng, and Yandong Liu
We propose to identify whether a sterile neutrino is Dirac-type or Majorana-type by counting the peak of the rapidity distribution at lepton colliders. Our method requires only one charged-lepton tagging, and the nature of sterile neutrinos can be pinned down once they are confirmed.
Phys. Rev. Lett. 134, 021801 (2025)
Extensions of fermion sector, Particle detection signatures, Heavy neutrinos, Majorana neutrinos, Lepton colliders
First Direct Search for Light Dark Matter Using the NEON Experiment at a Nuclear Reactor
Research article | Extensions of gauge sector | 2025-01-14 05:00 EST
J. J. Choi, C. Ha, E. J. Jeon, J. Y. Kim, K. W. Kim, S. H. Kim, S. K. Kim, Y. D. Kim, Y. J. Ko, B. C. Koh, S. H. Lee, I. S. Lee, H. Lee, H. S. Lee, J. S. Lee, Y. M. Oh, and B. J. Park (NEON Collaboration)
We report new results from the neutrino elastic scattering observation with NaI (NEON) experiment in the search for light dark matter (LDM) using $2636\text{ }\text{ }\mathrm{kg}\cdot{}\mathrm{days}$ of NaI(Tl) exposure. The experiment employs an array of NaI(Tl) crystals with a total mass of 16.7 kg, located 23.7 m away from a 2.8 GW thermal power nuclear reactor. We investigated LDM produced by the invisible decay of dark photons, a well-motivated mechanism generated by high-flux photons during reactor operation. The energy spectra collected during reactor-on and reactor-off periods were compared within the LDM signal region of 1–10 keV. No signal consistent with LDM interaction with electrons was observed, allowing us to set 90% confidence level exclusion limits on the dark matter-electron scattering cross section (${\sigma }{e}$) across dark matter masses ranging from 1 to $1000\text{ }\text{ }\mathrm{keV}/{\mathrm{c}}^{2}$. Our results set a 90% confidence level upper limit of ${\sigma }{e}=3.17\times{}{10}^{- 35}\text{ }\text{ }{\mathrm{cm}}^{2}$ for a dark matter mass of $100\text{ }\text{ }\mathrm{keV}/{\mathrm{c}}^{2}$, marking the best laboratory result in this mass range. Additionally, our search extends the coverage of LDM below $100\text{ }\text{ }\mathrm{keV}/{\mathrm{c}}^{2}$ for the first time, assuming the specific invisible decay of dark photons.
Phys. Rev. Lett. 134, 021802 (2025)
Extensions of gauge sector, Invisible decays, Particle dark matter
Deciphering Hypertriton and Antihypertriton Spins from Their Global Polarizations in Heavy-Ion Collisions
Research article | Particle & resonance production | 2025-01-14 05:00 EST
Kai-Jia Sun, Dai-Neng Liu, Yun-Peng Zheng, Jin-Hui Chen, Che Ming Ko, and Yu-Gang Ma
Understanding the properties of hypernuclei is crucial for constraining the nature of hyperon-nucleon ($Y\text{- }N$) interactions, which plays a key role in determining the inner structure of compact stars. The lightest hypernuclei and antihypernuclei are the hypertriton (${\mathrm{\Lambda }}^{3}\mathrm{H}$), which consists of a pair of nucleons and a $\mathrm{\Lambda }$ hyperon, and its antinucleus (${\overline{\mathrm{\Lambda }}}^{3}\overline{\mathrm{H}}$). Significant knowledge has recently been acquired regarding the mass, lifetime, and binding energy of $_{\mathrm{\Lambda }}^{3}\mathrm{H}$. However, its exact spin, whether $\frac{1}{2}$ or $\frac{3}{2}$, remains undetermined in both experimental and theoretical studies. Here, we present a novel method of using the hypertriton global polarization in heavy-ion collisions to decipher not only its total spin but also its internal spin structure. This method is based on the finding that its three different spin structures exhibit distinct beam energy dependence of its global polarization when it is produced in these collisions from the coalescence of proton, neutron and $\mathrm{\Lambda }$. Future observations of the hypertriton and antihypertriton global polarizations thus provide the opportunity to unveil the spin structures of hypertriton and antihypertriton and their production mechanisms in heavy-ion collisions.
Phys. Rev. Lett. 134, 022301 (2025)
Particle & resonance production, Quark-gluon plasma, Relativistic heavy-ion collisions
Stepping into the Sea of Instability: The New Sub-$\mathrm{\mu }\mathrm{s}$ Superheavy Nucleus $^{252}\mathrm{Rf}$
Research article | Fission | 2025-01-14 05:00 EST
J. Khuyagbaatar, P. Mosat, J. Ballof, R. A. Cantemir, Ch. E. Düllmann, K. Hermainski, F. P. Heßberger, E. Jäger, B. Kindler, J. Krier, N. Kurz, S. Löchner, B. Lommel, B. Schausten, Y. Wei, P. Wieczorek, and A. Yakushev
The discovery of an isotope, rutherfordium-252, whose ground state forestalls fission for just 60 nanoseconds, could help theorists understand the cosmic synthesis of superheavy elements.
Phys. Rev. Lett. 134, 022501 (2025)
Fission, Isomer decays, Nuclear structure & decays, A ≥ 220
First Identification of Excited States in $^{78}\mathrm{Zr}$ and Implications for Isospin Nonconserving Forces in Nuclei
Research article | Double beta decay | 2025-01-14 05:00 EST
G. L. Zimba et al.
At a fundamental level, the interactions between protons and protons, protons and neutrons, and neutrons and neutrons are not identical. Such isospin nonconserving interactions emerge when comparing the excitation energy of analog states in $T=1$ triplet nuclei. Here, we extend such an analysis to the $A=78$, $T=1$ triplet system—the heaviest system for which such complete data exists—and find strong disagreement with contemporary theory. This was achieved by pioneering the technique of recoil-$\beta \text{- }\beta $ tagging to identify excited states in $^{78}\mathrm{Zr}$. We also established a $^{78}\mathrm{Zr}$ half-life of ${25}_{- 8}^{+17}\text{ }\text{ }\mathrm{ms}$ and extended the $T=1$ band in $^{78}\mathrm{Y}$ to ${J}^{\pi }=({10}^{+})$.
Phys. Rev. Lett. 134, 022502 (2025)
Double beta decay, Nuclear forces, Nuclear structure & decays, Nucleon-nucleon interactions, 59 ≤ A ≤ 89, Density functional theory, Shell model, Spectrometers & spectroscopic techniques
Observation of Relaxation Stages in a Nonequilibrium Closed Quantum System: Decaying Turbulence in a Trapped Superfluid
Research article | Cold atoms & matter waves | 2025-01-14 05:00 EST
M. A. Moreno-Armijos, A. R. Fritsch, A. D. García-Orozco, S. Sab, G. Telles, Y. Zhu, L. Madeira, S. Nazarenko, V. I. Yukalov, and V. S. Bagnato
The dynamics of nonequilibrium closed quantum systems and their route to thermalization are of fundamental interest to several fields, from cosmology to particle physics. However, a comprehensive description of nonequilibrium phenomena still presents a significant challenge. In this work, we report the observation of distinct stages during the relaxation of the decaying turbulence in trapped Bose-Einstein condensates. Our findings show a direct particle cascade from low to high momenta, a consequence of the energy injection in the system, exhibiting a characteristic universal scaling. This stage is followed by an inverse particle cascade responsible for repopulating the previously depleted condensate. Both cascades can be explained through self-similar solutions provided by wave turbulence theory. These findings provide important insights into the relaxation stages of out-of-equilibrium quantum many-body systems.
Phys. Rev. Lett. 134, 023401 (2025)
Cold atoms & matter waves, Superfluidity, Turbulence, Bose-Einstein condensates, Nonequilibrium systems, Cooling & trapping
Quantum State Transfer via a Multimode Resonator
Research article | Cavity quantum electrodynamics | 2025-01-14 05:00 EST
Yang He and Yu-Xiang Zhang
Large-scale fault-tolerant superconducting quantum computation needs rapid quantum communication to network qubits fabricated on different chips and long-range couplers to implement efficient quantum error correction codes. Quantum channels used for these purposes are best modeled by multimode resonators, which lie between single-mode cavities and waveguides with a continuum of modes. In this Letter, we propose a non-Markovian formalism for quantum state transfer using coupling strengths comparable to the channel’s free spectral range ($g\sim {\mathrm{\Delta }}_{\mathrm{FSR}}$). Our scheme merges features of both the stimulated-Raman-adiabatic-passage-based methods for single-mode cavities and the pitch-and-catch protocol for long waveguides, integrating their advantages of low loss and high speed. It is immune to thermal channel occupations if using harmonic resonators for the sender and receiver.
Phys. Rev. Lett. 134, 023602 (2025)
Cavity quantum electrodynamics, Quantum control, Quantum state transfer, Stimulated Raman adiabatic passage, Superconducting qubits
Metasurface Polarization Optics: Phase Manipulation for Arbitrary Polarization Conversion Condition
Research article | Metasurfaces | 2025-01-14 05:00 EST
Siqi Li, Chen Chen, Guoxi Wang, Suyang Ge, Jiaqi Zhao, Xianshun Ming, Wei Zhao, Tao Li, and Wenfu Zhang
Metasurface polarization optics have attracted considerable attention due to their ability to manipulate independently the wave fronts of different polarization channels with subwavelength scale. Previous methods mainly focused on the condition of complete polarization conversion, restricting the application range of metasurface polarization multiplexing. Here, we proposed a generalized framework of phase manipulation for the metasurface polarization optics, which can realize independent phase control and arbitrary energy distribution of different polarization channels for the arbitrary polarization conversion efficiency. Based on this principle, we experimentally demonstrate tripolarization-channel wave-front control for the arbitrary polarization state (elliptical, circular, and linear). The arbitrary energy distribution of different polarization channels has been achieved via varying the polarization conversion efficiency. The proposed framework significantly improves the performance of metasurface in the polarization multiplexing and energy distribution, and expands the application scope of metasurface in the polarization optics.
Phys. Rev. Lett. 134, 023803 (2025)
Metasurfaces, Nanophotonics, Optical vortices
All-Optical Blast-Wave Control of Laser Wakefield Acceleration in a Near-Critical Plasma
Research article | Beam injection, extraction & transport | 2025-01-14 05:00 EST
I. Tsymbalov, D. Gorlova, K. Ivanov, E. Starodubtseva, R. Volkov, I. Tsygvintsev, Yu. Kochetkov, Ph. Korneev, A. Polonski, and A. Savel’ev
We propose a novel method for changing the length of laser wakefield electron acceleration in a gas jet using a cylindrical blast-wave created by a perpendicularly focused nanosecond laser pulse. The shock front modifies the wake significantly and stops interaction between the laser pulse and accelerated electron bunch, allowing one to directly control the interaction length and avoid dephasing. It also improves the electron beam quality through the plasma lensing effect between the two shock fronts. We demonstrated both experimentally and numerically how this approach can be used to form a quasimonoenergetic electron bunch with controlled energy and improved divergence as well as tracking changes in the bunch parameters during acceleration.
Phys. Rev. Lett. 134, 025101 (2025)
Beam injection, extraction & transport, Laser wakefield acceleration, Laser-plasma interactions, Relativistic multiple-particle dynamics, Shock waves & discontinuities in plasma, Laboratory plasma, Near-critical & underdense plasmas, Relativistic plasmas, Femtosecond laser irradiation, Fokker-Planck & Vlasov model, Hydrodynamic models, Optical interferometry, Optical plasma measurements, Particle-in-cell methods, Plasma diagnostic techniques
Nonlinear Superconducting Magnetoelectric Effect
Research article | Magnetoelectric effect | 2025-01-14 05:00 EST
Jin-Xin Hu, Oles Matsyshyn, and Justin C. W. Song
Supercurrent flow can induce a nonvanishing spin magnetization in noncentrosymmetric superconductors with spin-orbit interaction. Often known as the nondissipative magnetoelectric effect, these are most commonly found at linear order in supercurrent flow. Here, we propose that a nonlinear superconducting magnetoelectric (NSM) effect can naturally manifest in magnet-superconductor heterostructures. In such platforms, NSM manifests as the spin polarization generated as a second-order response to a driving supercurrent. Strikingly, we find NSM survives centrosymmetry and is the leading-order magnetic response in a variety of magnetic materials that include both collinear magnets (e.g., $d$-wave planar altermagnet thin film-superconductor) as well as noncollinear magnets (e.g., kagome-superconductor systems). This renders NSM a powerful electric and nondissipative means of controlling magnetization in magnet-superconductor heterostructures, a promising platform for superconducting spintronics.
Phys. Rev. Lett. 134, 026001 (2025)
Magnetoelectric effect, Superconductivity, Altermagnets
Temperature Dependence of Electron Viscosity in Superballistic GaAs Point Contacts
Research article | Ballistic transport | 2025-01-14 05:00 EST
Daniil I. Sarypov, Dmitriy A. Pokhabov, Arthur G. Pogosov, Evgeny Yu. Zhdanov, Andrey A. Shevyrin, Askhat K. Bakarov, and Alexander A. Shklyaev
Hydrodynamic description of collective electron motion turns out to be fruitful, since it provides a reliable physical concept that allows engineering the electron-electron interaction. We experimentally study the relation between two fundamental quantities—the electron viscosity and the Fermi quasiparticle lifetime—beyond the applicability limit of the Fermi liquid theory. We use point contact (PC) geometry to study electron transport and observe superballistic PC conductance, which is a signature of the electron viscosity. At high enough temperatures, the viscosity-lifetime relation is shown to diverge from the theoretically predicted one and turns out to be nontrivial. In addition, we study these phenomena in PCs freely suspended over a substrate, i.e., under the unique experimental conditions of enhanced electron-electron interaction. Suspension is found to reduce the electron viscosity in the whole temperature range, which makes the suspended structures a promising test bed for studying hydrodynamic effects in solids.
Phys. Rev. Lett. 134, 026302 (2025)
Ballistic transport, Interparticle interactions, Mesoscopics, Transport phenomena, Fermi liquid theory
Flat and Tunable Moir'e Phonons in Twisted Transition-Metal Dichalcogenides
Research article | Ferroelectricity | 2025-01-14 05:00 EST
Alejandro Ramos-Alonso, Benjamin Remez, Daniel Bennett, Rafael M. Fernandes, and Héctor Ochoa
An out-of-plane electric field can tune the phonon dispersion of twisted van der Waals multilayers.
Phys. Rev. Lett. 134, 026501 (2025)
Ferroelectricity, Phonons, Transition metal dichalcogenides, Twisted heterostructures, Domain walls, Lattice models in condensed matter, Multiscale modeling, Solitons
Fermionic Isometric Tensor Network States in Two Dimensions
Research article | 2-dimensional systems | 2025-01-14 05:00 EST
Zhehao Dai, Yantao Wu, Taige Wang, and Michael P. Zaletel
We generalize isometric tensor network states to fermionic systems, paving the way for efficient adaptations of 1D tensor network algorithms to 2D fermionic systems. As the first application of this formalism, we developed and benchmarked a time-evolving block-decimation (TEBD) algorithm for real-time and imaginary-time evolution. The imaginary-time evolution produces ground-state energies for gapped systems, systems with a Dirac point, and systems with gapless edge modes to good accuracy. The real-time TEBD captures the scattering of two fermions and the chiral edge dynamics on the boundary of a Chern insulator.
Phys. Rev. Lett. 134, 026502 (2025)
2-dimensional systems, Lattice models in condensed matter, Tensor network methods
Anomalous Spin and Orbital Hall Phenomena in Antiferromagnetic Systems
Research article | Antiferromagnetism | 2025-01-14 05:00 EST
J. E. Abrão, E. Santos, J. L. Costa, J. G. S. Santos, J. B. S. Mendes, and A. Azevedo
We investigate anomalous spin and orbital Hall phenomena in antiferromagnetic materials via orbital pumping experiments. Conducting spin and orbital pumping experiments on $\mathrm{YIG}/\mathrm{Pt}/{\mathrm{Ir}}{20}{\mathrm{Mn}}{80}$ heterostructures, we unexpectedly observe strong spin and orbital anomalous signals in an out-of-plane configuration. We report a sevenfold increase in the signal of the anomalous inverse orbital Hall effect compared to conventional effects. Our study suggests expanding the orbital Hall angle (${\theta }{\mathrm{OH}}$) to a rank 3 tensor, akin to the spin Hall angle (${\theta }{\mathrm{SH}}$), to explain the anomalous inverse orbital Hall effect. This work pioneers converting spin-orbital currents into charge currents, advancing the spin-orbitronics domain in antiferromagnetic materials.
Phys. Rev. Lett. 134, 026702 (2025)
Antiferromagnetism, Exchange bias, Magnetism, Spin current, Spin pumping, Spin-orbit coupling, Spintronics, Antiferromagnets, Epitaxy, Ferromagnetic resonance, Magneto-optical Kerr effect, Sputtering
Ultrafast Optical Control of Rashba Interactions in a TMDC Heterostructure
Research article | Excitons | 2025-01-14 05:00 EST
Henry Mittenzwey, Abhijeet M. Kumar, Raghav Dhingra, Kenji Watanabe, Takashi Taniguchi, Cornelius Gahl, Kirill I. Bolotin, Malte Selig, and Andreas Knorr
We investigate spin relaxation dynamics of interlayer excitons in a ${\mathrm{MoSe}}{2}/{\mathrm{MoS}}{2}$ heterostructure induced by the Rashba effect. In such a system, Rashba interactions arise from an out-of-plane electric field due to photogenerated interlayer excitons inducing a phonon-assisted intravalley spin relaxation. We develop a theoretical description based on a microscopic approach to quantify the magnitude of Rashba interactions and test these predictions via time-resolved Kerr rotation measurements. In agreement with the calculations, we find that the Rashba-induced intravalley spin mixing becomes the dominating spin relaxation channel above $T=70\text{ }\text{ }\mathrm{K}$. Our work identifies a previously unexplored spin-depolarization channel in heterostructures which can be used for ultrafast spin manipulation.
Phys. Rev. Lett. 134, 026901 (2025)
Excitons, Kerr effect, Phonons, Rashba coupling, Spin relaxation, Spin-orbit coupling, Valleytronics, Transition metal dichalcogenides
Strategy for Direct Detection of Chiral Phonons with Phase-Structured Free Electrons
Research article | Chirality | 2025-01-14 05:00 EST
Marc R. Bourgeois, Andrew W. Rossi, and David J. Masiello
Chiral phonons possessing valley pseudoangular momentum (PAM) underlie a diversity of quantum phenomena of fundamental and applied importance, but are challenging to probe directly. We show that deficiencies of typical momentum-resolved electron energy loss measurements that make it impossible to distinguish the PAM of chiral phonons can be overcome by introducing pinwheel free electron states with well-defined PAM. Transitions between such states generate 2D periodic arrays of in-plane field vortices with polarization textures tailored to selectively couple to desired chiral mode symmetries.
Phys. Rev. Lett. 134, 026902 (2025)
Chirality, Electron beams & optics, Phonons, Spin texture, Topological materials, Electron energy loss spectroscopy, Scanning transmission electron microscopy
Observation of Nonreciprocal Diffraction of Surface Acoustic Wave
Research article | Magnetoelastic effect | 2025-01-14 05:00 EST
Y. Nii, K. Yamamoto, M. Kanno, S. Maekawa, and Y. Onose
The rectification phenomenon caused by the simultaneous breaking of time-reversal and spatial inversion symmetries has been extended to a wide range of (quasi)particles and waves; however, nonreciprocal diffraction, which is the imbalance of upward and downward deflections, was previously observed only for photons and remained to be extended to other (quasi)particles. In this Letter, we present evidence of the nonreciprocal diffraction of a surface acoustic wave (SAW) utilizing a magnetoelastic grating on a SAW device. Asymmetric diffraction intensities were observed when the ferromagnetic resonance was acoustically excited. Based on a theoretical model, we attribute the microscopic origin of this phenomenon to the resonant scattering involving ferromagnetic resonance excitations. The novel property may pave an avenue to further development of SAW devices for various purposes, including microwave communications and quantum engineering applications.
Phys. Rev. Lett. 134, 027001 (2025)
Magnetoelastic effect, Magnons, Phononic crystals, Spin-phonon coupling, Ferromagnetic resonance, Surface acoustic wave
Physical Review X
Superconducting Quantum Oscillations and Anomalous Negative Magnetoresistance in a Honeycomb Nanopatterned Oxide Interface Superconductor
Research article | Interfaces | 2025-01-14 05:00 EST
Yishuai Wang, Siyuan Hong, Wenze Pan, Yi Zhou, and Yanwu Xie
Magnetoresistance measurements of an oxide-interface superconductor points to the potential of such materials as a platform for exploring exotic quantum states.
Phys. Rev. X 15, 011006 (2025)
Interfaces, Superconducting devices, Superconductors, Thin films, Two-dimensional electron system
arXiv
Ultrasensitive Electrochemical Sensor for Perfluorooctanoic Acid Detection Using Two-dimensional Aluminium Quasicrystal
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-01-15 20:00 EST
Anyesha Chakraborty, Raphael Tromer, Thakur Prasad Yadav, Nilay Krishna Mukhopadhyay, Basudev Lahiri, Rahul Rao, Ajit.K.Roy, Nirupam Aich, Cristiano F. Woellner, Douglas S. Galvao, Chandra Sekhar Tiwary
Per- and polyfluoroalkyl substances (PFAS), often referred as “forever chemicals,” are pervasive environmental pollutants due to their resistance to degradation. Among these, perfluorooctanoic acid (PFOA) poses significant threats to human health, contaminating water sources globally. Here, we have demonstrated the potential of a novel electrochemical sensor based on two-dimensional (2D) aluminium-based multicomponent quasicrystals (2D-Al QC) for the ultrasensitive sub-picomolar level detection of PFOA. The 2D-Al QC-inked electrode was employed here to detect PFOA by differential pulse voltammetry (DPV). The limit of detection (LoD) achieved is 0.59 +/- 0.05 pM. The sensor was evaluated for selectivity with other interfering compounds, repeatability of cycles, and reproducibility for five similar electrodes with a deviation of 0.8 %. The stability of the sensor has also been analysed after ninety days ,which shows a minimal variation of 15%. Spectroscopic techniques and theoretical calculations were further utilized to understand the interaction between the 2D-Al QC and PFOA. The results demonstrate that the 2D-Al QC offers a promising platform for the rapid and sensitive detection of PFOA, potentially addressing current environmental monitoring challenges.
Materials Science (cond-mat.mtrl-sci), Applied Physics (physics.app-ph), Chemical Physics (physics.chem-ph)
Three-dimensional (3D) tensor-based methodology for characterizing 3D anisotropic thermal conductivity tensor
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-01-15 20:00 EST
Dihui Wang, Heng Ban, Puqing Jiang
The increasing complexity of advanced materials with anisotropic thermal properties necessitates more generic and efficient methods to determine three-dimensional (3D) anisotropic thermal conductivity tensors with up to six independent components. Current methods rely on a vector-based framework that can handle only up to four independent components, often leading to inefficiencies and inaccuracies. We introduce Three-Dimensional Spatially Resolved Lock-In Micro-Thermography (3D SR-LIT), a novel optical thermal characterization technique combining a 3D tensor-based framework with an efficient area-detection experimental system. For simple tensors (e.g., x-cut quartz, k_xz=k_yz=0), our method reduces uncertainty by over 50% compared to vector-based methods. For complex tensors with six independent components (e.g., AT-cut quartz), 2{\sigma} uncertainties remain below 12% for all components. A novel adaptive mapping approach enables high-throughput data acquisition (40 seconds to 3 minutes, depending on tensor complexity), over 35 times faster than current methods, and accommodates samples with 200 nm surface roughness. Extensive numerical validation on 1,000 arbitrary anisotropic tensors ranging from 1 to 1,000 Wm^(-1) K^(-1) further validates the robustness of this methodology. This work highlights significant advancements in thermal characterization of complex anisotropic materials.
Materials Science (cond-mat.mtrl-sci), Data Analysis, Statistics and Probability (physics.data-an)
Problem hardness of diluted Ising models: Population Annealing vs Simulated Annealing
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-01-15 20:00 EST
Fernando Martínez-García, Diego Porras
Population annealing is a variant of the simulated annealing algorithm that improves the quality of the thermalization process in systems with rough free-energy landscapes by introducing a resampling process. We consider the diluted Sherrington-Kirkpatrick Ising model using population annealing to study its efficiency in finding solutions to combinatorial optimization problems. From this study, we find an easy-hard-easy transition in the model hardness as the problem instances become more diluted, and associate this behaviour to the clusterization and connectivity of the underlying Erdős-Rényi graphs. We calculate the efficiency of obtaining minimum energy configurations and find that population annealing outperforms simulated annealing for the cases close to this hardness peak while reaching similar efficiencies in the easy limits. Finally, it is known that population annealing can be used to define an adaptive inverse temperature annealing schedule. We compare this adaptive method to a linear schedule and find that the adaptive method achieves improved efficiencies while being robust against final temperature miscalibrations.
Statistical Mechanics (cond-mat.stat-mech), Disordered Systems and Neural Networks (cond-mat.dis-nn)
10 pages, 12 figures
Elastic Interaction of Pressurized Cavities in Hyperelastic Media: Attraction and Repulsion
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-01-15 20:00 EST
Ali Saeedi, Mrityunjay Kothari
This study computationally investigates the elastic interaction of two pressurized cylindrical cavities in a 2D hyperelastic medium. Unlike linear elasticity, where interactions are exclusively attractive, nonlinear material models (neo-Hookean, Mooney-Rivlin, Arruda-Boyce) exhibit both attraction and repulsion between the cavities. A critical pressure-shear modulus ratio governs the transition, offering a pathway to manipulate cavity configurations through material and loading parameters. At low ratios, the interactions are always attractive; at higher ratios, both attractive and repulsive regimes exist depending on the separation between the cavities. Effect of strain stiffening on these interactions are also analyzed. These insights bridge theoretical and applied mechanics, with implications for soft material design and subsurface engineering.
Soft Condensed Matter (cond-mat.soft)
7 pages and 7 figures in main text. 8 pages and 6 figures for appendix and references
Charge to spin conversion in atomically thin bismuth
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-01-15 20:00 EST
Wilson J. Yánez-Parreño, Alexander Vera, Sandra Santhosh, Chengye Dong, Jimmy C. Kotsakidis, Yongxi Ou, Saurav Islam, Adam L. Friedman, Maxwell Wetherington, Joshua Robinson, Nitin Samarth
We report charge to spin conversion in a hybrid heterostructure comprised of atomically thin bismuth (Bi) confined between a silicon carbide (SiC) substrate and epitaxial graphene (EG). We confirm composition, dimensionality, and a 96.5 % intercalation coverage using X-ray photolectron spectroscopy, scanning transmission microscopy, low energy electron diffraction, and Raman spectroscopy. Electrical transport measurements show signs of weak antilocalization in the heterostructure, consistent with spin-orbit coupling in this hybrid heterostructure. Spin torque ferromagnetic resonance measurements in permalloy/EG/2D-Bi heterostructures probe charge-to-spin conversion and revealing that an in plane polarization of the spin current, perpendicular to the charge current. The ratio of the in-plane to out-of-plane torque is 3.75 times higher than in hydrogenated graphene control samples.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Rare Events and Single Big Jump Effects in Ornstein-Uhlenbeck Processes
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-01-15 20:00 EST
Alberto Bassanoni, Alessandro Vezzani, Eli Barkai, Raffaella Burioni
Even in a simple stochastic process, the study of the full distribution of time integrated observables can be a difficult task. This is the case of a much-studied process such as the Ornstein-Uhlenbeck process where, recently, anomalous dynamical scaling of large deviations of time integrated functionals has been highlighted. Using the mapping of a continuous stochastic process to a continuous time random walk via the “excursions technique’’, we introduce a comprehensive formalism that enables the calculation of the complete distribution of the time-integrated observable $A = \int_0^T v^n(t) dt$, where $n$ is a positive integer and $v(t)$ is the random velocity of a particle following Ornstein-Uhlenbeck dynamics. We reveal an interesting connection between the anomalous rate function associated with the observable $A$ and the statistics of the area under the first-passage functional during an excursion. The rate function of the latter, analyzed here for the first time, exhibits anomalous scaling behavior and a dynamical phase transition, both of which are explored in detail. The case of the anomalous scaling of large deviations, originally associated to the presence of an instantonic solution in the weak noise regime of a path integral approach, is here produced by a so called “big jump effect’’, in which the contribution to rare events is dominated by the largest excursion. Our approach, which is quite general for continuous stochastic processes, allows to associate a physical meaning to the anomalous scaling of large deviations, through the big jump principle.
Statistical Mechanics (cond-mat.stat-mech)
26 pages, 6 figures
Quantum anomalous Hall effect for metrology
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-01-15 20:00 EST
Nathaniel J. Huáng, Jessica L. Boland, Kajetan M. Fijalkowski, Charles Gould, Thorsten Hesjedal, Olga Kazakova, Susmit Kumar, Hansjörg Scherer
The quantum anomalous Hall effect (QAHE) in magnetic topological insulators offers great potential to revolutionize quantum electrical metrology by establishing primary resistance standards operating at zero external magnetic field and realizing a universal “quantum electrical metrology toolbox” that can perform quantum resistance, voltage and current metrology in a single instrument. To realize such promise, significant progress is still required to address materials and metrological challenges – among which, one main challenge is to make the bulk of the topological insulator sufficiently insulating to improve the robustness of resistance quantization. In this Perspective, we present an overview of the QAHE; discuss the aspects of topological material growth and characterization; and present a path towards an QAHE resistance standard realized in magnetically doped (Bi,Sb)$_2$Te$_3$ systems. We also present guidelines and methodologies for QAHE resistance metrology, its main limitations and challenges as well as modern strategies to overcome them.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Materials Science (cond-mat.mtrl-sci), Quantum Physics (quant-ph)
15 pages, 4 figures
Electrical Control of the Exchange Bias Effect at Ferromagnet-Altermagnet Junctions
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-01-15 20:00 EST
Gaspar De la Barrera, Alvaro S. Nunez
This work analyzes the behavior of the interface between a ferromagnetic material and an alter-magnet. We use a well-established line of arguments based on electronic mean-field calculations to show that new surface phenomena that lead to altermagnetic materials induce an exchange bias effect on the nearby ferromagnet. We reveal the physical mechanisms behind this phenomenon that lead to quantitative control over its strength. Interestingly, we predict exotic electric-field-induced phenomena. This is an analogy to the relationship between exchange bias and the injection of spin currents in spin-transfer-dominated scenarios, which has been reported earlier in the traditional antiferromagnetic/ferromagnetic junction.
Materials Science (cond-mat.mtrl-sci), Other Condensed Matter (cond-mat.other)
7 pages, 5 figures
Ensemble inequivalence in the design of mixtures with super-Gibbs phase coexistence
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-01-15 20:00 EST
Filipe C. Thewes, Peter Sollich
Designing the phase behavior of multicomponent mixtures is a rich area with many potential applications. One key question is how more than $M+1$ phases, as would normally be allowed by Gibbs’ phase rule at generic temperature in a mixture of $M$ molecular species, can be made to coexist in equilibrium. In the grandcanonical ensemble, such super-Gibbs phase equilibria can be realized by tuning the interactions among the $M$ species. This introduces $\sim M^2$ additional degrees of freedom and hence a superlinear number of phases that can coexist. We show that, surprisingly, there is no straightforward equivalence to the situation in the experimentally relevant canonical ensemble: here only a subset of the grandcanonical phases will generically be realized. This subset is determined by interfacial tensions in addition to bulk free energies. Using a graph-theoretical approach, we determine a sufficient set of inequalities for the interfacial tensions for which all grandcanonical phases are realized so that equivalence of ensembles is effectively restored. We illustrate the design method for a two-component mixture with four coexisting phases and point out the route for generalizing this to a higher number of components.
Statistical Mechanics (cond-mat.stat-mech), Soft Condensed Matter (cond-mat.soft)
Optimal Control of an Electromechanical Energy Harvester
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-01-15 20:00 EST
Dario Lucente, Alessandro Manacorda, Andrea Plati, Alessandro Sarracino, Marco Baldovin
Many techniques originally developed in the context of deterministic control theory have been recently applied to the quest for optimal protocols in stochastic processes. Given a system subject to environmental fluctuations, one may ask what is the best way to change in time its controllable parameters in order to maximize, on average, a certain reward function, while steering the system between two pre-assigned states. In this work we study the problem of optimal control for a wide class of stochastic systems, inspired by a model of energy harvester. The stochastic noise in this system is due to the mechanical vibrations, while the reward function is the average power extracted from them. We consider the case in which the electrical resistance of the harvester can be changed in time, and we exploit the tools of control theory to work out optimal solutions in a perturbative regime, close to the stationary state. Our results show that it is possible to design protocols that perform better than any possible solution with constant resistance.
Statistical Mechanics (cond-mat.stat-mech)
Rigorous bound on diffusion for chaotic spin chains
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-01-15 20:00 EST
Dimitrios Ampelogiannis, Benjamin Doyon
The emergence of diffusion is one of the deepest physical phenomena observed in many-body interacting, chaotic systems. But establishing rigorously that correlation functions, say of the energy density, expand diffusively, remains one of the most important problems of mathematical physics. We show for the first time that diffusion is non-zero in almost every chaotic nearest-neighbor interacting quantum spin chain (spin-1/2, without magnetic field), at high enough temperatures. A chaotic system is defined in the precise sense that the Hilbert space of extensive charges is one-dimensional. Thus, under the widely expected assumption that almost every nearest-neighbor spin chain is indeed chaotic, we find that almost every nearest-neighbor spin chain has non-zero diffusion. Our main tool is the Green-Kubo formula for diffusivity, the mathematical technique of projection over quadratically extensive charges, and appropriate correlation decay bounds recently established. Our methods can be extended to finite or short ranges, magnetic field and higher spins. As we argue, according to the theory of nonlinear fluctuating hydrodynamics, we further expect almost every nearest-neighbor interacting quantum spin chain to display superdiffusion, and thus have infinite diffusivity; however this is still beyond the reach of mathematical rigour.
Statistical Mechanics (cond-mat.stat-mech)
5 pages; 2 pages appendix
Band Structure Modeling of Perovskite Materials with Quantum ESPRESSO for Multijunction Photovoltaic Cell Optimization
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-01-15 20:00 EST
Increasing photovoltaic conversion efficiency, or PCE, has proven to be a critical factor in the transition to renewable energy. There exist strong interdependencies between the perovskite crystals and multijunction architectures within photovoltaic cell research. In present literature, there is a lack of intersection in investigating crystallographic geometry and compositional engineering with representation of computational modeling systems. In this paper, we propose a novel method for the rapid discovery of high-efficiency perovskite-based multijunction cells, specifically with silicon as the low band gap absorbing semiconductor material. We model the spatial geometries of potential perovskite candidates for high-efficiency cells using the Schrodinger Material Science Maestro, optimizing the periodic boundary conditions on the unit cell to minimize edge-bound errors. Band structure calculations using density functional theory become effective to approximate the PCE. After careful adjustments to the ibrav lattice parameter and parallelization, Quantum ESPRESSO was optimized for perovskite multijunction band structure calculations. Computational results on the six test-perovskite configurations demonstrate the effectiveness and superiority of our proposed representation and method, with a calculated efficiency of about 46% for one of the modeled perovskites, placing it at the top of high-efficiency perovskite-Si multijunction cells. With this method, the potential exists to bring forth a new generation of photovoltaic cells that are easily manufacturable, highly efficient, and economical.
Materials Science (cond-mat.mtrl-sci), Computational Physics (physics.comp-ph)
TeNeS-v2: Enhancement for Real-Time and Finite Temperature Simulations of Quantum Many-Body Systems
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-01-15 20:00 EST
Yuichi Motoyama, Tsuyoshi Okubo, Kazuyoshi Yoshimi, Satoshi Morita, Tatsumi Aoyama, Takeo Kato, Naoki Kawashima
Quantum many-body systems are challenging targets for computational physics due to their large degrees of freedom. The tensor networks, particularly Tensor Product States (TPS) and Projected Entangled Pair States (PEPS), effectively represent these systems on two-dimensional lattices. However, the technical complexity of TPS/PEPS-based coding is often too much for researchers to handle. To reduce this problem, we developed TeNeS (Tensor Network Solver). This paper introduces TeNeS-v2, which extends TeNeS with real-time and finite temperature simulations, providing deeper insights into quantum many-body systems. We detail the new algorithms, input/output design, and application examples, demonstrating TeNeS-v2’s applicability to various quantum spin and Bose models on two-dimensional lattices.
Strongly Correlated Electrons (cond-mat.str-el), Statistical Mechanics (cond-mat.stat-mech), Computational Physics (physics.comp-ph)
10 pages, 8 figures
Thermal Annealing and Radiation Effects on Structural and Electrical Properties of NbN/GaN Superconductor/Semiconductor Junctions
New Submission | Superconductivity (cond-mat.supr-con) | 2025-01-15 20:00 EST
Stephen Margiotta, Binzhi Liu, Saleh Ahmed Khan, Gabriel Calderon Ortiz, Ahmed Ibreljic, Jinwoo Hwang, A F M Anhar Uddin Bhuiyan
In the rapidly evolving field of quantum computing, niobium nitride (NbN) superconductors have emerged as integral components due to their unique structural properties, including a high superconducting transition temperature (Tc), exceptional electrical conductivity, and compatibility with advanced device architectures. This study investigates the impact of high-temperature annealing and high-dose gamma irradiation on the structural and superconducting properties of NbN films grown on GaN via reactive DC magnetron sputtering. The as-deposited cubic {\delta}-NbN (111) films exhibited a high-intensity XRD peak, high Tc of 12.82K, and an atomically flat surface. Annealing at 500 and 950 °C for varying durations revealed notable structural and surface changes. High-resolution STEM indicated improved local ordering, while AFM showed reduced surface roughness after annealing. XPS revealed a gradual increase in the Nb/N ratio with higher annealing temperatures and durations. High-resolution XRD and STEM analyses showed lattice constant modifications in {\delta}-NbN films, attributed to residual stress changes following annealing. Additionally, XRD phi-scans revealed sixfold symmetry in NbN films due to rotational domains relative to GaN. While Tc remained stable after annealing at 500 °C, increasing the annealing temperature to 950 °C degraded Tc to ~8K and reduced the residual resistivity ratio from 0.85 in as-deposited films to 0.29 after 30 minutes. The effects of gamma radiation (5 Mrad (Si)) were also studied, demonstrating minimal changes to crystallinity and superconducting performance, indicating excellent radiation resilience. These findings highlight the potential of NbN superconductors for integration into advanced quantum devices and their suitability for applications in radiation-intensive environments such as space, satellites, and nuclear power plants.
Superconductivity (cond-mat.supr-con), Quantum Physics (quant-ph)
Sub-critical athermal flow in disordered materials caused by periodic variations of environmental conditions
New Submission | Disordered Systems and Neural Networks (cond-mat.dis-nn) | 2025-01-15 20:00 EST
Ezequiel E. Ferrero, Eduardo A. Jagla
Yield stress materials deform irreversibly at a finite strain-rate if loaded with a fixed stress $\sigma$ larger than some critical yield stress $\sigma_c$. When $\sigma<\sigma_c$ deformation is only transient, unless thermal activation plays a role, in which case persistent deformation occurs as a creep activated process. Yet in subcritical athermal conditions we observe that cyclic time variation of system parameters can induce a steady-state flow, with a total deformation that scales linearly with the number of cycles applied. We characterize this phenomenon using well established models in the fields of depinning and yielding transitions. Interestingly, there is an endurance limit $\sigma_0<\sigma_c$ for this process to occur, below which the advance is totally suppressed. We discuss implications of our findings to the study of sub-critical evolution of landforms in which periodic variations of external conditions (as for instance daily/seasonal cycles of temperature, humidity, etc.) are expected.
Disordered Systems and Neural Networks (cond-mat.dis-nn), Soft Condensed Matter (cond-mat.soft), Statistical Mechanics (cond-mat.stat-mech), Geophysics (physics.geo-ph)
15 pages, 17 figures
DSMC: A Statistical Mechanics Perspective
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-01-15 20:00 EST
This paper presents a perspective in which Direct Simulation Monte Carlo (DSMC) is viewed not in its traditional role as an algorithm for solving the Boltzmann equation but as a numerical method for statistical mechanics. First, analytical techniques such as the collision virial and Green-Kubo relations, commonly used in molecular dynamics, are used to study the numerical properties of the DSMC algorithm. The stochastic aspect of DSMC, which is often viewed as unwanted numerical noise, is shown to be a useful feature for problems in statistical physics, such as Brownian motion and thermodynamic fluctuations. Finally, it is argued that fundamental results from statistical mechanics can provide guardrails when applying machine learning to DSMC.
Statistical Mechanics (cond-mat.stat-mech)
Simulations of Three-dimensional Nematic Guidance of Microswimmers
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-01-15 20:00 EST
Zeyang Mou, Yuan Li, Zhihong You, Rui Zhang
It has been shown that an anisotropic liquid crystalline (LC) environment can be used to guide the self-propulsion dynamics of dispersed microswimmers, such as bacteria. This type of composite system is named “living nematic” (LN). In the dilute limit, bacteria are found to mainly follow the local director field. Beyond the dilute limit, however, they exhibit novel dynamical behaviors, from swirling around a spiral +1 defect pattern to forming undulating waves, and to active turbulence. Our current knowledge of how these different behaviors emerge at different population densities remains limited. Here we develop a hybrid method to simulate the dynamics of microswimmers dispersed in a nematic LC. Specifically, we model the microswimmers using active Brownian dynamics method, which is coupled to a hydrodynamic model of nematic LCs to describe the evolution of the flow field and the LC structure. Our method is validated by comparing to existing quasi-two-dimensional (2D) experiments, including undulated swirling around a spiral pattern and stabilized undulated jets on a periodic C-pattern. We further extend our method to three-dimensional (3D) systems by examining loop-defect dynamics. We find that the morphodynamics and destiny of a loop defect not only depend on the activity (self-propulsion velocity), effective size, and the initial distribution of the swimmers, but also rely on its winding profile. Specifically, +1/2 wedge and radial twist winding can dictate the dynamics of loop defects. By varying the characteristic reversal time, we predict that microswimmers not necessarily accumulate in splay regions. Taken together, our hybrid method provides a faithful tool to explain and guide the experiments of LNs in both 2D and 3D, sheds light on the interplay between microswimmer distribution and defect dynamics, and unravels the design principles of using LCs to control active matter.
Soft Condensed Matter (cond-mat.soft), Biological Physics (physics.bio-ph), Fluid Dynamics (physics.flu-dyn)
13 pages, 6 figures
Origin of dimensional crossover in quasi-one-dimensional hollandite K${2}$Ru${8}$O$_{16}$
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-01-15 20:00 EST
Asif Ali, Sakshi Bansal, B. H. Reddy, Ravi Shankar Singh
Intriguing phenomenon of dimensional crossover is comprehensively studied by experimental and theoretical investigation of electronic structure in quasi-one-dimensional hollandite K${2}$Ru${8}$O$_{16}$. Valence band photoemission spectra in conjunction with density functional theory within local density approximation combined with dynamical mean field theory (LDA+DMFT) reveal moderately correlated electronic structure. Anomalous temperature dependence of high-resolution spectra in the vicinity of Fermi level suggests Tomonaga-Luttinger liquid state down to 150 K, below which it undergoes a dimensional crossover from one-dimensional to three-dimensional electronic behaviour. Monotonously decreasing spectral intensity at the Fermi level along with Fermi cut-off at low temperature suggests non-Fermi liquid like behaviour. Many body effects captured within LDA+DMFT reveal increased warping of the Fermi surface with lowering temperature. A simple analysis suggests that the warping dominates the thermal energy induced momentum broadening at low temperature, leading to the 3D electronic behaviour. Our results offer valuable insight in understanding the interplay of dimensionality, electron correlation and thermal energy governing various exotic phenomena in quasi-one-dimensional systems.
Strongly Correlated Electrons (cond-mat.str-el)
to appear in Phys. Rev. B
Robust triple-q magnetic order with trainable spin vorticity in Na$_2$Co$_2$TeO$_6$
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-01-15 20:00 EST
Xianghong Jin, Mengqiao Geng, Fabio Orlandi, Dmitry Khalyavin, Pascal Manuel, Yang Liu, Yuan Li
Recent studies suggest that the candidate Kitaev magnet Na$_2$Co$_2$TeO$_6$ possesses novel triple-$\mathbf{q}$ magnetic order instead of conventional single-$\mathbf{q}$ zigzag order. Here we present dedicated experiments in search for distinct properties expected of the triple-$\mathbf{q}$ order, namely, insensitivity of the magnetic domains to weak $C_3$ symmetry-breaking fields and fictitious magnetic fields generated by the spin vorticity. In structurally pristine single crystals, we show that $C_3$ symmetry-breaking in-plane uniaxial strains do not affect the order’s magnetic neutron diffraction signals. We further show that $\mathbf{c}$-axis propagating light exhibits large Faraday rotations in the ordered state due to the spin vorticity, the sign of which can be trained via the system’s ferrimagnetic moment. These results are in favor of the triple-$\mathbf{q}$ order in Na$_2$Co$_2$TeO$_6$ and reveal its unique emerging behavior.
Strongly Correlated Electrons (cond-mat.str-el)
4 pages, 4 figures, plus Supplemental Material
Multifractal-enriched mobility edges and emergent quantum phases in one-dimensional exactly solvable lattice models
New Submission | Disordered Systems and Neural Networks (cond-mat.dis-nn) | 2025-01-15 20:00 EST
Shan-Zhong Li, Yi-Cai Zhang, Yucheng Wang, Shanchao Zhang, Shi-Liang Zhu, Zhi Li
We propose a class of exactly solvable flat-band quasiperiodic lattice models that encompass a variety of multifractal-enriched mobility edges and multi-state coexisting quantum phases. Utilizing Avila’s global theory, we derive exact expressions of the Lyapunov exponents in both lattice and dual spaces, providing an analytical expression and phase diagram for the multifractal-enriched mobility edges. Additionally, we numerically compute the inverse participation ratios of the eigenstates in both real and dual spaces to further characterize these phases. Furthermore, we demonstrate that these models can be realized using Rydberg atomic arrays, enabling the observation of Lyapunov exponents and inverse participation ratios through a powerful spectroscopy approach.
Disordered Systems and Neural Networks (cond-mat.dis-nn), Quantum Physics (quant-ph)
5+22 pages, 4+16 figures
Heterarchical Granular Dynamics
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-01-15 20:00 EST
Benjy Marks, Shivakumar Athani, Itai Einav
The two most commonly used methods to model the behaviour of granular flows are discrete element and continuum mechanics simulations. These approaches concentrate on the deterministic description of particle or bulk material motion. Unlike these approaches, this paper introduces an alternative model that describes the stochastic dynamics of the void spaces under the action of gravity. The model includes several key phenomena which are observed in deforming granular media, such as segregation, mixing, and an angle of repose. These mechanisms are modelled heterarchically using both spatial and microstructural internal coordinates. Key aspects of the model include its ability to describe both stable and flowing states of granular media based on a solid fraction cut-off, and the influence of particle size on flow, segregation, and mixing. The model is validated with simulations of column collapse and silo discharge.
Soft Condensed Matter (cond-mat.soft)
Disorder-Induced Slow Relaxation of Phonon Polarization
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-01-15 20:00 EST
The role of the polarization degree of freedom in lattice dynamics in solids has been underlined recently. We theoretically discover a relaxation mechanism for both linear and circular polarizations of acoustic phonons. In the absence of scattering, the polarization exhibits oscillatory behavior. This behavior leads to a counterintuitive result: unlike linear momentum, more frequent scattering events cause slower polarization relaxation due to motional narrowing. We validate this mechanism using the quantum kinetic equation. We derive the relaxation rates of polarizations analytically for isotropic elastic bodies and numerically for a cubic crystal. Remarkably, we reveal that linear polarizations relax more slowly than circular ones. Our findings provide a pathway to extend the lifetime of phonon angular momentum.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Main text (6 pages, 3 figures) + supplementary material (10 pages)
Algorithm to generate hierarchical structure of desiccation crack patterns
New Submission | Disordered Systems and Neural Networks (cond-mat.dis-nn) | 2025-01-15 20:00 EST
Yuri Yu. Tarasevich, Andrei V. Eserkepov, Irina V. Vodolazskaya
We propose an algorithm generating planar networks which structure resembles a hierarchical structure of desiccation crack patterns.
Disordered Systems and Neural Networks (cond-mat.dis-nn), Computational Physics (physics.comp-ph)
4 pages, 6 figures, 1 table, 18 refs
Structural and Physical Properties of the Heavy Fermion Metal Ce$_2$NiAl$_6$Si$_5$
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-01-15 20:00 EST
Jiawen Zhang, Jinyu Wu, Ye Chen, Rui Li, Michael Smidman, Yu Liu, Yu Song, Huiqiu Yuan
Strongly correlated electrons at the verge of quantum criticality give rise to unconventional phases of matter and behaviors, with the discovery of new quantum critical materials driving synergistic advances in both experiments and theory. In this work, we report the structural and physical properties of a new quaternary Ce-based heavy fermion compound, Ce$_2$NiAl$_6$Si$_5$, synthesized using the self-flux method. This compound forms a layered tetragonal structure (space group $P4/nmm$), with square nets of Ce atoms separated by Si-Al or Ni-Si-Ge layers. Specific heat measurements show a low temperature Sommerfeld coefficient of 1.4 J/mol-Ce K$^{2}$, with a reduced entropy indicative of significant Kondo interactions. Below 0.6 K, an upturn in resistivity and a deviation in magnetic susceptibility suggest the appearance of magnetic ordering or the development of dynamic magnetic correlations, which is further supported by a bulge in specific heat around 0.4 K. These results suggest that Ce$_2$NiAl$_6$Si$_5$ is a layered heavy fermion metal, naturally located in proximity to a spin-density-wave quantum critical point.
Strongly Correlated Electrons (cond-mat.str-el), Materials Science (cond-mat.mtrl-sci)
7 pages, 5 figures
Chinese Physics Letters 41, 127304 (2024)
Magnetic Interactions in the Polar Ferrimagnet with a Bipartite Structure
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-01-15 20:00 EST
Junbo Liao, Zhentao Huang, Bo Zhang, Yanyan Shangguan, Shufan Cheng, Hao Xu, Zihang Song, Shuai Dong, Devashibhai Adrojia, Song Bao, Jinsheng Wen
The polar magnets A$_2$Mo$_3$O$_8$ (A=Fe, Mn, Co, and Ni) feature a bipartite structure, where the magnetic A$^{2+}$ ions occupy two different sites with octahedral and tetrahedral oxygen coordinations. This bipartite structure provides a platform for the emergence of nontrivial magnetoelectric (ME) effects and intriguing excitation behaviors, and thus creates significant research interest. In this study, we conduct inelastic neutron scattering measurements on single crystals of Mn$_2$Mo$_3$O$_8$, an L-type ferrimagnet in the A$_2$Mo$_3$O$_8$ family, to investigate its spin dynamics. The obtained magnetic excitation spectra reveal two distinct magnon dispersions corresponding to the octahedral and tetrahedral spins in Mn$2$Mo$3$O$8$. These magnon bands can be well described by a spin Hamiltonian including Heisenberg and single-ion anisotropy terms. Employing our effective spin model, we successfully reproduce the unusual temperature dependence of the L-type ferrimagnetic susceptibility through self-consistent mean-field theory. This research reveals the significance of the bipartite structure in determining the excitation properties of the polar magnets $\rm{A{2}Mo{3}O{8}}$ and provides valuable insights into the spin dynamics of L-type ferrimagnets.
Strongly Correlated Electrons (cond-mat.str-el), Materials Science (cond-mat.mtrl-sci)
8 pages, 5 figues, published in PRB
Phys. Rev. B 111, 024407 (2025)
Excitonic oscillator-strength saturation dominates polariton-polariton interactions
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-01-15 20:00 EST
Maxime Richard, Irénée Frérot, Sylvain Ravets, Jacqueline Bloch, Carlos Anton-Solanas, Ferdinand Claude, Yueguang Zhou, Martina Morassi, Aristide Lemaître, Iacopo Carusotto, and Anna Minguzzi
Exciton-polaritons in semiconductor microcavities exhibit large two-body interactions that, thanks to ever refined nanotechnology techniques, are getting closer and closer to the quantum regime where single-photon nonlinearities start being relevant. To foster additional progress in this direction, in this work we experimentally investigate the microscopic mechanism driving polariton-polariton interactions. We measure the dispersion relation of the collective excitations that are thermally generated on top of a coherent fluid of interacting lower-polaritons. By comparing the measurements with the Bogoliubov theory over both the lower and upper polariton branches simultaneously, we find that polariton-polariton interactions stem dominantly from a mechanism of saturation of the exciton oscillator strength.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Quantum Gases (cond-mat.quant-gas)
Mean-squared Energy Difference for Exploring Potential Energy Landscapes of Supercooled Liquids
New Submission | Disordered Systems and Neural Networks (cond-mat.dis-nn) | 2025-01-15 20:00 EST
Dianmo Zhang, Deyan Sun, Xingao Gong
By extending the concept of diffusion to the potential energy landscapes (PELs), we introduce the mean-squared energy difference (MSED) as a novel quantity to investigate the intrinsic properties of glass. MSED can provide a clear description of the “energy relaxation” process on a PEL. Through MSED analysis, we can obtain characteristic timescale similar to those from structure analysis, namely $\tau_\alpha^\ast$. We establish a connection between MSED and the properties of PELs, providing a concise and quantitative description of the PEL. We find that the roughness of the accessible PEL has changed significantly after the glass transition. And we also find that one of the PEL parameters is closely related to the Adam-Gibbs configurational entropy. The present research, which directly links the PEL to the relaxation process, provides avenues for further research of the glass.
Disordered Systems and Neural Networks (cond-mat.dis-nn), Computational Physics (physics.comp-ph)
16 pages, 4 figures
Magnon-induced scalar spin chirality in Kagome and honeycomb ferromagnets
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-01-15 20:00 EST
Nanse Esaki, Gyungchoon Go, Se Kwon Kim
The scalar spin chirality (SSC), defined as a triple product of spins, is essential for describing noncoplanar spin structures and understanding chiral physics in magnetic systems. Traditionally, SSC has been discussed primarily in the context of noncoplanar ground-state spin configurations at zero temperature, as collinear spin systems are generally thought to lack SSC. Consequently, whether the SSC can emerge at finite temperatures in spin systems with collinear ground states remains an open question and has yet to be fully understood. In this study, we theoretically demonstrate that thermally excited magnons can induce SSC even in collinear spin systems. By considering 2D ferromagnets on Kagome and honeycomb lattices, we demonstrate that the Dzyaloshinskii-Moriya interactions (DMI) which break the effective time-reversal symmetry in the magnon Hamiltonian can lead to finite SSC at finite temperatures. Using a simple spin model, we show both numerically and analytically that the SSC increases with the magnitude of DMI and temperature. Furthermore, calculations based on realistic material parameters reveal that the magnon-induced SSC can achieve a magnitude comparable to those observed in non-coplanar spin configurations. These findings suggest that SSC plays a significant role even in collinear spin systems, providing new insights into the chiral physics of magnetic materials.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
10 pages, 5 figures
Effect of helium surface fluctuations on the Rydberg transition of trapped electrons
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-01-15 20:00 EST
Mikhail Belianchikov, Natalia Morais, Denis Konstantinov
Electrons trapped on the surface of liquid helium is an extremely clean system which holds promise for a scalable qubit platform. However, the superfluid surface is not free from fluctuations which might cause the decay and dephasing of the electrons quantized states. Understanding and mitigating these fluctuations is essential for the advancement of electrons-on-helium (eHe) qubit technology. Some work has been recently done to investigate surface oscillations due to the mechanical vibration of the cryostat using a superconducting coplanar waveguide (CPW) resonator. In the present work, we focus on a sub-hertz frequency range and observe a strong effect of surface oscillations on the temporal dynamics of the Rydberg transition of electrons confined in a microchannel trapping device. We suggest possible origin of such oscillations and find a reasonable agreement between the corresponding estimation of the oscillation frequency and the observed result.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Quantum Gases (cond-mat.quant-gas), Applied Physics (physics.app-ph)
10 pages, 4 figures
Some observations on the ambivalent role of symmetries in Bayesian inference problems
New Submission | Disordered Systems and Neural Networks (cond-mat.dis-nn) | 2025-01-15 20:00 EST
We collect in this note some observations on the role of symmetries in Bayesian inference problems, that can be useful or detrimental depending on the way they act on the signal and on the observations. We emphasize in particular the need to gauge away unobservable invariances in the definition of a distance between a signal and its estimator, and the consequences this implies for the statistical mechanics treatment of such models, taking as a motivating example the extensive rank matrix factorization problem.
Disordered Systems and Neural Networks (cond-mat.dis-nn), Statistical Mechanics (cond-mat.stat-mech), Information Theory (cs.IT), Probability (math.PR), Statistics Theory (math.ST)
14 pages
Exploring the energy spectrum of a four-terminal Josephson junction: Towards topological Andreev band structures
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-01-15 20:00 EST
Tommaso Antonelli, Marco Coraiola, David Christian Ohnmacht, Aleksandr E. Svetogorov, Deividas Sabonis, Sofieke C. ten Kate, Erik Cheah, Filip Krizek, Rüdiger Schott, Juan Carlos Cuevas, Wolfgang Belzig, Werner Wegscheider, Fabrizio Nichele
Hybrid multiterminal Josephson junctions (JJs) are expected to harbor a novel class of Andreev bound states (ABSs), including topologically nontrivial states in four-terminal devices. In these systems, topological phases emerge when ABSs depend on at least three superconducting phase differences, resulting in a three-dimensional (3D) energy spectrum characterized by Weyl nodes at zero energy. Here, we realize a four-terminal JJ in a hybrid Al/InAs heterostructure, where ABSs form a synthetic 3D band structure. We probe the energy spectrum using tunneling spectroscopy and identify spectral features associated with the formation of a tri-Andreev molecule, a bound state whose energy depends on three superconducting phases and, therefore, is able to host topological ABSs. The experimental observations are well described by a numerical model. The calculations predict the appearance of four Weyl nodes at zero energy within a gap smaller than the experimental resolution. These topological states are theoretically predicted to remain stable within an extended region of the parameter space, well accessible by our device. These findings establish an experimental foundation to study high-dimensional synthetic band structures in multiterminal JJs, and to realize topological Andreev bands.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Superconductivity (cond-mat.supr-con)
Quasiparticle Fermi surfaces of niobium and niobium-titanium alloys at high pressure
New Submission | Superconductivity (cond-mat.supr-con) | 2025-01-15 20:00 EST
D. Jones, A. Östlin, A. Chmeruk, F. Beiuşeanu, U. Eckern, L. Vitos, L. Chioncel
The electronic structure of pure niobium and the niobium-titanium alloy Nb${0.44}$Ti${0.56}$ in the bcc-phase at pressures up to $250$ GPa is investigated, to reveal possible factors conducing toward the robust superconductivity reported for Ti-doped niobium upon a considerable volume reduction. We model the structural disorder using the coherent potential approximation, and the electronic correlations are taken into account using dynamical mean-field theory. At high pressure, a significant change in the topology of the Fermi surface is observed, while electronic correlations weaken with increasing pressure. Thus, the normal state of Nb${0.44}$Ti${0.56}$ is found to be a Fermi liquid with a well-defined Fermi surface, and well-defined quasiparticles near it. The systematic study of the impact of disorder upon the Fermi surface at such ultra high pressures allows notable insights into the nature of the electronic states near the Fermi level, i.e., within the energy scale relevant for superconducting pairing. Furthermore, our results clearly indicate the necessity of further experimental Fermi surface explorations.
Superconductivity (cond-mat.supr-con), Strongly Correlated Electrons (cond-mat.str-el)
Superconductivity and normal-state transport in compressively strained La$_2$PrNi$_2$O$_7$ thin films
New Submission | Superconductivity (cond-mat.supr-con) | 2025-01-15 20:00 EST
Yidi Liu, Eun Kyo Ko, Yaoju Tarn, Lopa Bhatt, Berit H. Goodge, David A. Muller, Srinivas Raghu, Yijun Yu, Harold Y. Hwang
The discovery of superconductivity under high pressure in Ruddlesden-Popper phases of bulk nickelates has sparked great interest in stabilizing ambient pressure superconductivity in thin-film form using epitaxial strain. Recently, signs of superconductivity have been observed in compressively strained bilayer nickelate thin films with an onset temperature exceeding 40 K, albeit with broad and two-step-like transitions. Here, we report intrinsic superconductivity and normal-state transport properties in compressively strained La$_2$PrNi$_2$O$_7$ thin films, achieved through a combination of isovalent Pr substitution, growth optimization, and precision ozone annealing. The superconducting onset occurs above 48 K, with zero resistance reached above 30 K, and the critical current density at 1.4 K is 100-fold larger than previous reports. The normal-state resistivity exhibits quadratic temperature dependence indicative of Fermi liquid behaviour, and other phenomenological similarities to transport in overdoped cuprates suggest parallels in their emergent properties.
Superconductivity (cond-mat.supr-con), Materials Science (cond-mat.mtrl-sci)
18 pages, 4 figures
Enhancing Spin Diffusion in GaAs Quantum Wells: The Role of Electron Density and Channel Width
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-01-15 20:00 EST
B. W. Grobecker, A. V. Poshakinskiy, S. Anghel, T. Mano, G. Yusa, M. Betz
This study explores the relationship between spin diffusion, spin lifetime, electron density and lateral spatial confinement in two-dimensional electron gases hosted in GaAs quantum wells. Using time-resolved magneto-optical Kerr effect microscopy, we analyze how Hall-bar channel width and back-gate voltage modulation influence spin dynamics. The results reveal that the spin diffusion coefficient increases with reduced channel widths, a trend further amplified at lower electron concentrations achieved via back-gate voltages, where it increases up to 150% for the narrowest channels. The developed theoretical model confirms the spatial inhomogeneities in the spin diffusion as arising from electron-density variations within the channels. The results underscore the importance of tuning electron density and spatial geometry to optimize spin transport and coherence, providing valuable design considerations for spintronic devices where efficient spin manipulation is crucial.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
A rational framework to estimate the chiroptical activity of [6]Helicene Derivatives
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-01-15 20:00 EST
Mirko Vanzan, Susanna Bertuletti, Belen Bazan, Minze T. Rispens, Steven I. C. Wan, Michel Leeman, Willem L. Noorduin, Francesca Baletto
Helicenes are a class of molecules potentially suitable in several technological applications with intrinsic structural chirality which makes them interesting scaffolds for chiroptical properties. As desirable is tuning chiroptical property by synthesis, we combine experimental optical characterization and ab-initio calculations to study how different substituents influence the optical properties of [6]helicene. We explore anchoring groups presenting a variety of sizes and chemical nature, finding that both electron withdrawing and donating groups redshift and dwindle the optical activity of the molecule. We suggest the observed dumping in transitions energy and intensity is connected to the strength of the perturbation induced by the substituent on the pi-conjugation of the aromatic rings. Such observations demonstrate how helicenes’ chiroptical properties can be fine-tuned via stereochemical control of the substituents and validates a simple yet effective computational setup to model the optics of those systems.
Materials Science (cond-mat.mtrl-sci)
Magnetic Dichroism in Rutile NiF$_2$: Separating Altermagnetic and Ferromagnetic Effects
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-01-15 20:00 EST
A. Hariki, K. Sakurai, T. Okauchi, J. Kuneš
We present numerical simulations of x-ray magnetic circular dichroism (XMCD) at the L$_{2,3}$ edge of Ni in the weakly ferromagnetic altermagnet NiF$_2$. Our results predict a significant XMCD signal for light propagating perpendicular to the magnetic moments, which are approximately aligned along the [100] easy-axis direction. The analysis shows that the altermagnetic and ferromagnetic contributions to the XMCD signal can be uniquely distinguished by their dependence on an applied magnetic field. By varying the angle of the field relative to the easy axis, the in-plane orientation of both the Néel vector and the net magnetization can be systematically controlled. We further demonstrate that the XMCD signal, even under fields as strong as 40 T and for any in-plane orientation, can be accurately described as a linear combination of two spectral components, with geometrical prefactors determined by the field magnitude and direction. This insight enables experimental validation of the distinctive relationship between the Néel vector orientation and the x-ray Hall vector in the rutile structure. Quantitative simulations supporting these findings are provided.
Materials Science (cond-mat.mtrl-sci), Strongly Correlated Electrons (cond-mat.str-el)
6 pages, 6 figures, supplemental material
Hydrodynamics-driven phase-locking and collective motility of sessile active dumbbells
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-01-15 20:00 EST
Urvi Mahendra Bora, Mohd Suhail Rizvi
Collective motion is a phenomenon observed across length scales in nature, from bacterial swarming and tissue migration to the flocking of animals. The mechanisms underlying this behavior vary significantly depending on the biological system, ranging from hydrodynamic and chemical interactions in bacteria to mechanical forces in epithelial tissues and social alignment in animal groups. While collective motion often arises from the coordinated activity of independently motile agents, this work explores a novel context: the emergence of collective motion in systems of non-motile active agents. Inspired by the oscillatory shape dynamics observed in suspended cells such as neutrophils and fibroblasts, we model active dumbbells exhibiting limit-cycle oscillations in shape as a minimal representation of such this http URL computational simulations, we demonstrate that hydrodynamic interactions between these dumbbells lead to three key phenomena: a density-dependent transition from sessile to collective motion, hydrodynamics-induced phase separation, and synchronization of oscillatory shape changes. We have explored the role of hydrodynamic interactions on these emergent properties of sessile active dumbbells. These results underscore the critical role of hydrodynamic coupling in enabling and organizing collective behaviors in systems lacking intrinsic motility. This study lays the groundwork for future investigations into the emergent behavior of active matter and its implications for understanding cell motility, tissue dynamics, and the development of bio-inspired materials.
Soft Condensed Matter (cond-mat.soft), Biological Physics (physics.bio-ph)
The impact of alloying elements on the precipitation stability and kinetics in iron based alloys: An atomistic study
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-01-15 20:00 EST
Giovanni Bonny, Christophe Domain, Nicolas Castin, Pär Olsson, Lorenzo Malerba
Iron based industrial steels typically contain a large number of alloying elements, even so-called low alloyed steels. Under irradiation, these alloying elements form clusters that have a detrimental impact of the mechanical properties of the steel. The stability and formation mechanisms of such clusters are presently not fully understood. Therefore, in this work, we study the thermal stability and formation kinetics of small solute clusters in the bcc Fe matrix. We use density functional theory (DFT) to characterize the binding energy of vacancy/solute clusters containing Cr, Mn, Ni, Cu, Si and P, thereby exploring>700 different configurations. The constructed DFT data base is used to fit a cluster expansion (CE) for the vacancy-FeCrMnNiCuSiP system. In turn, the obtained CE is applied in atomistic kinetic Monte Carlo simulations to study the effect of Mn, Ni, Cr, Si and P on the precipitation formation in the FeCu alloy. We conclude that the addition of Mn and Ni delay the precipitation kinetics by an order of magnitude. The additional alloying with traces of P/Si further delays the kinetics by an additional order of magnitude. We found that Si plays an essential role in the formation of spatially mixed MnNiCuSi cluster.
Materials Science (cond-mat.mtrl-sci)
30 pages, 9 figures, accepted manuscript
Computational Materials Science 161 (2019) 309-320
Double Microwave Shielding
New Submission | Quantum Gases (cond-mat.quant-gas) | 2025-01-15 20:00 EST
Tijs Karman, Niccolò Bigagli, Weijun Yuan, Siwei Zhang, Ian Stevenson, Sebastian Will
We develop double microwave shielding, which has recently enabled evaporative cooling to the first Bose-Einstein condensate of polar molecules [Bigagli et al., Nature 631, 289 (2024)]. Two microwave fields of different frequency and polarization are employed to effectively shield polar molecules from inelastic collisions and three-body recombination. Here, we describe in detail the theory of double microwave shielding. We demonstrate that double microwave shielding effectively suppresses two- and three-body losses. Simultaneously, dipolar interactions and the scattering length can be flexibly tuned, enabling comprehensive control over interactions in ultracold gases of polar molecules. We show that this approach works for a wide range of molecules. This opens the door to studying many-body physics with strongly interacting dipolar quantum matter.
Quantum Gases (cond-mat.quant-gas), Atomic and Molecular Clusters (physics.atm-clus), Atomic Physics (physics.atom-ph), Chemical Physics (physics.chem-ph), Quantum Physics (quant-ph)
Theoretical determination of Gilbert damping in reduced dimensions
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-01-15 20:00 EST
Balázs Nagyfalusi, László Szunyogh, Krisztián Palotás
An ab initio scheme based on the linear response theory of exchange torque correlation is presented to calculate intrinsic Gilbert damping parameters in magnets of reduced dimensions. The method implemented into the real-space Korringa-Kohn-Rostoker (RS-KKR) Greens’ function framework enables to obtain diagonal elements of the atomic-site-dependent on-site and non-local Gilbert damping tensor. Going from the 3D bulk and surfaces of iron and cobalt ferromagnets addressed in our previous work [Phys. Rev. B 109, 094417 (2024)], in the present paper monolayers of Fe and Co on (001)- and (111)-oriented Cu, Ag, and Au substrates are studied, and particularly the substrate-dependent trends are compared. Furthermore, the Gilbert damping parameters are calculated for Fe and Co adatoms and dimers on (001)-oriented substrates. It is investigated how the damping parameter of single adatoms depends on their vertical position. This dependence is quantified in relation to the adatoms’ density of states at the Fermi energy showing a non-monotonic behavior. By rotating the spin moment of the adatoms and collinear magnetic dimers, an anisotropic behavior of the damping is revealed. Finally, a significant, three- to ten-times increase of the on-site Gilbert damping is found in antiferromagnetic dimers in comparison to the ferromagnetic ones, whilst the inter-site damping is even more enhanced.
Materials Science (cond-mat.mtrl-sci)
12 pages, 6 figures, 8 tables, submitted to Phys. Rev. B
Intricately Entangled Spin and Charge Diffusion and the Coherence-Incoherence Crossover in the High-Dimensional Hubbard Model
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-01-15 20:00 EST
Gopal Prakash, S.R.Hassan, M.S. Laad, N.S.Vidhyadhiraja, T.V.Ramakrishnan
Correlation-driven metal-insulator transitions and temperature-driven quantum-coherent-to-incoherent crossovers in correlated electron systems underpin the doping, temperature and frequency-resolved evolution of physical responses. Motivated by recent experimental studies that investigate the evolution of dynamical spin and charge responses, we analyze the spin and charge diffusion spectra in both half-filled and doped one-band Hubbard model using Dynamical Mean Field Theory (DMFT) combined with the Numerical Renormalization Group (NRG). We compare the relative strengths and limitations of Density Matrix NRG (DMNRG) and Full Density Matrix NRG (FDM-NRG) in capturing low-frequency spectral features and their evolution with temperature, interaction strength and band-filling. Key measures, including characteristic frequency scales, Kullback-Leibler divergence, diffusion constants, and kurtosis provide complementary but internally consistent picture for the evolution of spin and charge excitations across bandwidth as well as the band-filling driven Mott transitions and the coherent-incoherent crossover. We find that spin and charge fluctuations cross over from quantum-coherent-to-quantum-incoherent at distinct temperatures, providing a microscopic insight into the complex, two-stage, Fermi-to-non-Fermi liquid-to-bad metal crossovers seen in transport data, in particular in the $dc$ resistivity.
Strongly Correlated Electrons (cond-mat.str-el)
Origin of perpendicular magnetic anisotropy in ultra-thin metal films studied by in-situ neutron reflectometry
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-01-15 20:00 EST
Grigorii Kirichuk, Alexey Grunin, Artur Dolgoborodov, Pavel Prokopovich, Petr Shvets, Alexey Vorobiev, Anton Devishvilli, Alexandr Goikhman, Ksenia Maksimova
Perpendicular magnetic anisotropy (PMA) plays an important role in different spintronic devices. The rapid development of spintronics requires a better understanding of the nature and mechanisms of the PMA formation. In our article, we demonstrate the potential of studying PMA by in-situ polarized neutron reflectometry combined with pulsed laser deposition. Using these techniques, we show the formation of out-of-plane anisotropy in thin CoFeB films (1.8 nm) with a capping Mo layer. Investigating thick (5.3 nm}) and thin (0.5 nm) molybdenum films, we demonstrate that in both cases, PMA was established in bilayer structures without any thermal annealing. Also, we demonstrate how an additional silicon layer grown over the CoFeB/Mo bilayer can critically alter the magnetic properties of the sample. Such studies are possible only through the unique combination of the growth method with the in-situ polarized neutron reflectometry measurement technique. We believe that this approach will open up broad opportunities for the development and investigation of new spintronic devices.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Materials Science (cond-mat.mtrl-sci), Nuclear Experiment (nucl-ex)
12 pages, 5 figures
Two dimensional transition metal dichalcogenide based bilayer heterojunctions for efficient solar cells and photocatalytic applications
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-01-15 20:00 EST
Khushboo Dange, Rachana Yogi, Alok Shukla
This work presents a first-principles study of the optoelectronic properties of vertically-stacked bilayer heterostructures composed of 2D transition-metal dichalcogenides (TMDs). The calculations are performed using the density-functional theory (DFT) and many-body perturbation theory within $G_0W_0$-BSE methodology. We aim to propose these TMD heterostructures for solar cell applications. The TMD monolayers comprising the heterojunctions considered in this work are $MoS_2$, $WS_2$, $MoSe_2$, and $WSe_2$ due to their favorable band gaps, high carrier mobility, robust absorption in the visible region, and excellent stability. These four TMD monolayers provide the basis for six heterostructures. Consequently, we have examined the structural, electronic, and optical properties of six heterostructures ($WS_2/MoS_2$, $MoSe_2/MoS_2$, $MoSe_2/WS_2$, $WSe_2/MoS_2$, $WSe_2/MoSe_2$, and $WSe_2/WS_2$). At the DFT level, all the six considered TMD heterostructures meet the essential criterion of type II band alignment, a critical factor in extending carrier lifetime. However, according to $G_0W_0$ results, $MoSe_2/WS_2$ does not exhibit the type II band alignment, instead it shows type I band alignment. The large quasiparticle gaps obtained from $G_0W_0$ approximation suggest the presence of strong electron-correlation effects. The quality of these heterojunction solar cells is estimated by computing their power conversion efficiencies (PCE). The PCEs are calculated at both the HSE06 and $G_0W_0$ levels, and the maximum PCE predicted by HSE06 calculations on our designed solar cells can reach up to 19.25% for the $WSe_2/WS_2$ heterojunction. In addition, all six TMD heterostructures are examined for their potential applications in photocatalysis for hydrogen evolution reaction, and the three of them, namely, $WS_2/MoS_2$, $MoSe_2/MoS_2$, and $WSe_2/MoS_2$ heterostructures qualify for the same.
Materials Science (cond-mat.mtrl-sci)
49 pages (40 pages Manuscript and 9 pages Supporting Material), 9 figures and 11 tables in the manuscript, and 7 figures and 6 tables in the Supporting Material
Phys. Rev. Applied 23, 014008, 2025
Electron-phonon coupling and phonon dynamics in single-layer NbSe$_2$ on graphene: the role of moir'e phonons
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-01-15 20:00 EST
Amjad Al Taleb, Wen Wan, Giorgio Benedek, Miguel M. Ugeda, Daniel Farías
The interplay between substrate interactions and electron-phonon coupling in two-dimensional (2D) materials presents a significant challenge in understanding and controlling their electronic properties. Here, we present a comparative study of the structural characteristics, phonon dynamics, and electron-phonon interactions in bulk and monolayer NbSe$_2$ on epitaxial bilayer graphene (BLG) using helium atom scattering (HAS). High-resolution helium diffraction reveals a (9x9)0$^{\circ}$ superstructure within the NbSe$2$ monolayer, commensurate with the BLG lattice, while out-of-plane HAS diffraction spectra indicate a low-corrugated (3$\sqrt{3}$x3$\sqrt{3}$)30$^{\circ}$ substructure. By monitoring the thermal attenuation of the specular peak across a temperature range of 100 K to 300 K, we determined the electron-phonon coupling constant $\lambda{HAS}$ as 0.76 for bulk 2H-NbSe$_2$. In contrast, the NbSe$2$ monolayer on graphene exhibits a reduced $\lambda{HAS}$ of 0.55, corresponding to a superconducting critical temperature (T$_C$) of 1.56 K according to the MacMillan formula, consistent with transport measurement findings. Inelastic HAS data provide, besides a set of dispersion curves of acoustic and lower optical phonons, a soft, dispersionless branch of phonons at 1.7 meV, attributed to the interface localized defects distributed with the superstructure period, and thus termed moiré phonons. Our data show that moiré phonons contribute significantly to the electron-phonon coupling in monolayer NbSe$_2$. These results highlight the crucial role of the BLG on the electron-phonon coupling in monolayer NbSe$_2$, attributed to enhanced charge transfer effects, providing valuable insights into substrate-dependent electronic interactions in 2D superconductors.
Materials Science (cond-mat.mtrl-sci), Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Strongly Correlated Electrons (cond-mat.str-el), Superconductivity (cond-mat.supr-con)
Observation of zero coefficient of friction above a critical pressure
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-01-15 20:00 EST
Weipeng Chen, Tielin Wu, Yelingyi Wang, Deli Peng, Jin Wang, Zhanghui Wu, Quanshui Zheng
Self-superlubricity is a highly anticipated phenomenon where certain solid pairs in contact, without lubricant, exhibit zero wear and virtually null static friction and coefficient of friction (CoF). We present the first experimental observation of self-superlubricity in a microscale single-crystalline graphite flake in contact with a nanoscale-rough Au substrate, achieved when the applied normal pressure exceeds a critical threshold. Theoretical analysis revealed that substrate roughness impedes full contact at low pressures, but increasing the pressure induces a transition to full contact, enabling self-superlubricity. We established a dimensionless criterion for this critical pressure, further validated by observing self-superlubricity between graphite and an atomically smooth sapphire substrate without requiring additional pressure. This breakthrough introduces a transformative principle for next-generation microsystems such as micro/nanoscale generators, motors, oscillators, sensors, etc., enabling reduced power consumption and extended operational lifetimes in applications such as 6G communication, humanoid robotics, and unmanned aerial vehicles.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Experimentally Probing Non-Hermitian Spectral Transition and Eigenstate Skewness
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-01-15 20:00 EST
Jia-Xin Zhong, Jeewoo Kim, Kai Chen, Jing Lu, Kun Ding, Yun Jing
Non-Hermitian (NH) systems exhibit intricate spectral topology arising from complex-valued eigenenergies, with positive/negative imaginary parts representing gain/loss. Unlike the orthogonal eigenstates of Hermitian systems, NH systems feature left and right eigenstates that form a biorthogonal basis and can differ significantly, showcasing pronounced skewness between them. These characteristics give rise to unique properties absent in Hermitian systems, such as the NH skin effect and ultra spectral sensitivity. However, conventional experimental techniques are inadequate for directly measuring the complex-valued spectra and left and right eigenstates – key elements for enhancing our knowledge of NH physics. This challenge is particularly acute in higher-dimensional NH systems, where the spectra and eigenstates are highly sensitive to macroscopic shapes, lattice geometry, and boundary conditions, posing greater experimental demands compared to one-dimensional systems. Here, we present a Green’s function-based method that enables the direct measurement and characterization of both complex-valued energy spectra and the left and right eigenstates in arbitrary NH lattices. Using active acoustic crystals as the experimental platform, we observe spectral transitions and eigenstate skewness in two-dimensional NH lattices under both nonreciprocal and reciprocal conditions, with varied geometries and boundary conditions. Our approach renders complex spectral topology and left eigenstates experimentally accessible and practically meaningful, providing new insights into these quantities. The results not only confirm recent theoretical predictions of higher-dimensional NH systems but also establish a universal and versatile framework for investigating complex spectral properties and NH dynamics across a wide range of physical platforms.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Quantum Physics (quant-ph)
Pb-intercalated epitaxial graphene on SiC: Full insight into band structure and orbital character of interlayer Pb, and charge transfer into graphene
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-01-15 20:00 EST
Bharti Matta, Philipp Rosenzweig, Kathrin Küster, Craig Polley, Ulrich Starke
Intercalation is a robust approach for modulating the properties of epitaxial graphene on SiC and stabilizing two-dimensional (2D) intercalant layers at the graphene/SiC interface. In this work, we present synchrotron-based angle resolved photoelectron spectroscopy (ARPES) measurements focussing on the band structure of intercalated Pb under a single layer of epitaxial graphene. The interlayer Pb exhibits a metallic character, a $(1 \times 1)$ registry with respect to SiC, and free electron-like bands to a first order. Divergences from the free electron approximation include various band splittings and gaps throughout the Pb Brillouin zone. Light polarization dependent ARPES measurements indicate a predominant out-of-plane orbital character for the Pb bands, suggesting potential interactions between the interlayer Pb and graphene’s $\pi$ orbitals that may induce proximity effects in graphene. Density functional theory (DFT) calculations for a $(1 \times 1)$ Pb monolayer on SiC show a reasonable qualitative agreement with the experimentally observed interlayer bands as well as the polarization dependent measurements. Finally, temperature dependent ARPES measurements reveal that the nearly charge-neutral graphene layer involves charge transfer from both the interlayer Pb and the substrate SiC.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Materials Science (cond-mat.mtrl-sci)
11 pages and 6 figures (and 3 pages of supplementary information with 6 figures)
Ferroelectric Properties of van der Waals Chalcogenides: DFT perspective
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-01-15 20:00 EST
Xue Li, James G. McHugh, Vladimir I. Falko
Layered materials with non-centrosymmetric stacking order are attracting increasing interest due to the presence of ferroelectric polarization, which is dictated by weak interlayer hybridization of atomic orbitals. Here, we use density functional theory modelling to systematically build a library of van der Waals chalcogenides that exhibit substantial ferroelectric polarization. For the most promising materials, we also analyse the pressure dependence of the ferroelectric effect and charge accumulation of photo-induced electrons and holes at surfaces and internal twin boundaries in thin films of such materials.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Materials Science (cond-mat.mtrl-sci)
12 pages, 5 figures
Resolving Structural Origins for Superconductivity in Strain-Engineered La$_3$Ni$_2$O$_7$ Thin Films
New Submission | Superconductivity (cond-mat.supr-con) | 2025-01-15 20:00 EST
Lopa Bhatt, Abigail Y. Jiang, Eun Kyo Ko, Noah Schnitzer, Grace A. Pan, Dan Ferenc Segedin, Yidi Liu, Yijun Yu, Yi-Feng Zhao, Edgar Abarca Morales, Charles M. Brooks, Antia S. Botana, Harold Y. Hwang, Julia A. Mundy, David A. Muller, Berit H. Goodge
The discovery of high-temperature superconductivity in bulk La$_3$Ni$_2$O$_7$ under high hydrostatic pressure and, more recently, biaxial compression in epitaxial thin films has ignited significant interest in understanding the interplay between atomic and electronic structure in these compounds. Subtle changes in the nickel-oxygen bonding environment are thought to be key drivers for stabilizing superconductivity, but specific details of which bonds and which modifications are most relevant remains so far unresolved. While direct, atomic-scale structural characterization under hydrostatic pressure is beyond current experimental capabilities, static stabilization of strained La$_3$Ni$_2$O$_7$ films provides a platform well-suited to investigation with new picometer-resolution electron microscopy methods. Here, we use multislice electron ptychography to directly measure the atomic-scale structural evolution of La$_3$Ni$_2$O$_7$ thin films across a wide range of biaxial strains tuned via substrate. By resolving both the cation and oxygen sublattices, we study strain-dependent evolution of atomic bonds, providing the opportunity to isolate and disentangle the effects of specific structural motifs for stabilizing superconductivity. We identify the lifting of crystalline symmetry through modification of the nickel-oxygen octahedral distortions under compressive strain as a key structural ingredient for superconductivity. Rather than previously supposed $c$-axis compression, our results highlight the importance of in-plane biaxial compression in superconducting thin films, which suggests an alternative – possibly cuprate-like – understanding of the electronic structure. Identifying local regions of inhomogeneous oxygen stoichiometry and high internal strain near crystalline defects, we suggest potential pathways for improving the sharpness and temperature of the superconducting transition.
Superconductivity (cond-mat.supr-con)
4 figures, 3 tables, 15 supplemental figures
A modular quantum gas platform
New Submission | Quantum Gases (cond-mat.quant-gas) | 2025-01-15 20:00 EST
Tobias Hammel, Maximilian Kaiser, Daniel Dux, Philipp M. Preiss, Matthias Weidemüller, Selim Jochim
We report on the development of a modular platform for programmable quantum simulation with atomic quantum gases. The platform is centered around exchangeable optical modules with versatile functionalities. The performance of each module is disentangled from all others, enabling individual validation and maintenance of its outputs. The relative spatial positioning of the modules with respect to the position of the atomic sample is set by a global reference frame. In this way, the platform simplifies re-configuration and upgrading of existing setups and accelerates the design of new machines in a time- and cost-efficient manner. Furthermore, it facilitates collaboration among different experimental groups. This standardized hardware design framework, which we call Heidelberg Quantum Architecture, paves the way towards a new generation of on-demand and highly adaptable quantum simulation experiments.
Quantum Gases (cond-mat.quant-gas), Quantum Physics (quant-ph)
Negative superfluid density and spatial instabilities in driven superconductors
New Submission | Superconductivity (cond-mat.supr-con) | 2025-01-15 20:00 EST
Andrey Grankin, Victor Galitski, Vadim Oganesyan
We consider excitation of Higgs modes via the modulation of the BCS coupling within the Migdal-Eliashberg-Keldysh theory of time-dependent superconductivity. Despite the presence of phonons, which break integrability, we observe Higgs amplitude oscillations reminiscent of the integrable case. The dynamics of quasiparticles follows from the effective Bogolyubov-de Gennes equations, which represent a Floquet problem for the Bogoliubov quasiparticles. We find that when the Floquet-Bogoliubov bands overlap, the homogeneous solution formally leads to a negative superfluid density, which is no longer proportional to the amplitude of the order parameter. This result indicates an instability, which we explore using spatially-resolved BdG equations. Spontaneous appearance of spatial inhomogeneities in the order parameter is observed and they first occur when the superfluid density becomes unphysical. We conclude that the homogeneous solution to time-dependent superconductivity is generally unstable and breaks up into a complicated spatial landscape via an avalanche of topological excitations.
Superconductivity (cond-mat.supr-con)
Guided modes in graphene waveguides
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-01-15 20:00 EST
Fan-Ming Zhang, Ying He, Xi Chen
By analogy of optical waveguides, we investigate the guided modes in graphene waveguides, which is made of symmetric quantum well. The unique properties of the graphene waveguide are discussed based on the two different dispersion relations, which correspond to classical motion and Klein tunneling, respectively. It is shown that the third-order mode is absent in the classical motion, while the fundamental mode is absent in the Klein tunneling case. We hope these phenomena can lead to the potential applications in graphene-based quantum devices.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
4 pages, 4 figures
Appl. Phys. Lett. 94, 212105 (2009)
Phononic frictional losses of a particle crossing a crystal: linear-response theory
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-01-15 20:00 EST
Gabriele Riva, Giacomo Piscia, Nicolas Trojani, Giuseppe E. Santoro, Erio Tosatti, Nicola Manini
We address weak-coupling frictional sliding with phononic dissipation by means of analytic many-body techniques.
Our model consists of a particle (the “slider”) moving through a two- or three-dimensional crystal and interacting weakly with its atoms, and therefore exciting phonons.
By means of linear-response theory we obtain explicit expressions for the friction force slowing down the slider as a function of its speed, and compare them to the friction obtained by simulations, demonstrating a remarkable accord.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Other Condensed Matter (cond-mat.other)
23 pages, 11 figures
Tunable lateral displacement and spin beam splitter for ballistic electrons in two-dimensional magnetic-electric nanostructures
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-01-15 20:00 EST
Xi Chen, Chun-Fang Li, Yue Ban
We investigate the lateral displacements for ballistic electron beams in a two-dimensional electron gas modulated by metallic ferromagnetic (FM) stripes with parallel and antiparallel (AP) magnetization configurations. It is shown that the displacements are negative as well as positive, which can be controlled by adjusting the electric potential induced by the applied voltage and the magnetic field strength of FM stripes. Based on these phenomena, we propose an efficient way to realize a spin beam splitter, which can completely separate spin-up and spin-down electron beams in the AP configuration by their corresponding spatial positions.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
5 pages, 4 figures,
Phys. Rev. B 77, 073307 (2008)
OstravaJ: a tool for calculating magnetic exchange interactions via DFT
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-01-15 20:00 EST
OstravaJ is a Python package for high-throughput calculation of exchange interaction terms in the Heisenberg model for magnetic materials. It uses the total energy difference method, where calculations are based on the total energy of the system in different magnetic configurations, calculated by means of density functional theory. OstravaJ can propose a suitable set of magnetic configurations, generate VASP configuration files in cooperation with the user, and read VASP calculation results, which minimizes necessary human interaction. It can also calculate other relevant properties (e. g. MFA and RPA critical temperature, spin-wave stiffness) and provide input for various atomistic spin dynamics codes.
We present results for a number of materials from various classes (metals, transition metal oxides), compared to other methods. They show that the total energy difference method is a useful method for exchange interaction calculation from first principles.
Materials Science (cond-mat.mtrl-sci)
Ultrashort Carbon Nanotubes with Luminescent Color Centers are Ultrabright NIR-II Nano-Emitters
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-01-15 20:00 EST
Somen Nandi, Quentin Gresil, Benjamin P. Lambert, Finn L. Sebastian, Simon Settele, Ivo Calaresu, Juan Estaun-Panzano, Anna Lovisotto, Claire Mazzocco, Benjamin S. Flavel, Erwan Bezard, Laurent Groc, Jana Zaumseil, Laurent Cognet
Combining brightness and nanoscale size of short-wave infrared (SWIR) emitters is equally essential in the fields of bioimaging, photonics, and quantum science, but such nano-emitters are still lacking. Here we report that when functionalized with luminescent color centers, ultrashort carbon nanotubes with lengths much shorter than 100 nm, are surprisingly bright in the near-infrared second-biological window (NIR-II) of the SWIR. We discuss the origin of this exceptional brightness based on the uncontrollable presence of quenching defects in solubilized carbon nanotubes. The observed NIR-II brightness exceeds that of well-known visible emitters, including quantum dots. After being made biocompatible, ultrashort carbon nanotubes with luminescent color centers open the route toward point-spread function engineering and 3-dimensional single-particle studies for nanoscale NIR-II imaging in thick brain tissue.
Materials Science (cond-mat.mtrl-sci), Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Optics (physics.optics)
33 pages, 5 figures
Integer Quantum Hall Effect: Disorder, temperature, floating, and plateau width
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-01-15 20:00 EST
Stuart Yi-Thomas, Yi Huang, Jay D. Sau, Sankar Das Sarma
We theoretically consider disorder and temperature effects on the integer quantum Hall effect (IQHE) using a variety of distinct and complementary analytical and numerical techniques. In particular, we address simple, physical, and experimentally relevant questions: How does disorder and/or temperature affect the IQHE plateau width? Does the plateau width increase or decrease with disorder and/or temperature? What happens to the peak in the longitudinal conductance with increasing disorder/temperature? Does the longitudinal conductance obey any universal scaling property? Is there “floating” with increasing disorder and/or decreasing magnetic field? Can disorder destroy the IQHE? Is there an IQHE to localization transition? What is the Landau level dependence of the plateau width? Our detailed theory provides answers to these and other related experimentally relevant questions. We discuss our results in the context of existing experimental results and suggest future experiments arising from our work. A key finding is that disorder and temperature are intrinsically connected in affecting IQHE, and there is an intricate interplay between them leading to nonmonotonicity in how the IQHE plateau width behaves as a function of increasing disorder. Both must be considered on an equal footing in understanding IQHE experiments.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
23 pages, 17 figures
Frequency Fluctuations in Nanomechanical Resonators due to Quantum Defects
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-01-15 20:00 EST
M. P. Maksymowych, M. Yuksel, O. A. Hitchcock, N. R. Lee, F. M. Mayor, W. Jiang, M. L. Roukes, A. H. Safavi-Naeini
Nanomechanical resonators promise diverse applications ranging from mass spectrometry to quantum information processing, requiring long phonon lifetimes and frequency stability. Although two-level system (TLS) defects govern dissipation at millikelvin temperatures, the nature of frequency fluctuations remains poorly understood. In nanoscale devices, where acoustic fields are confined to sub-wavelength volumes, strong coupling to individual TLS should dominate over weak coupling to defect ensembles. In this work, we monitor fast frequency fluctuations of phononic crystal nanomechanical resonators, while varying temperature ($10$ mK$-1$ K), drive power ($10^2-10^5$ phonons), and the phononic band structure. We consistently observe random telegraph signals (RTS) which we attribute to state transitions of individual TLS. The frequency noise is well-explained by mechanical coupling to individual far off-resonant TLS, which are either thermally excited or strongly coupled to thermal fluctuators. Understanding this fundamental decoherence process, particularly its RTS structure, opens a clear path towards noise suppression for quantum and sensing applications.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Applied Physics (physics.app-ph), Quantum Physics (quant-ph)
18 pages, 5 main figures, 2 supplementary figures
Surface and Bulk Two-Level System Losses in Lithium Niobate Acoustic Resonators
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-01-15 20:00 EST
Rachel G. Gruenke-Freudenstein, Erik Szakiel, Gitanjali P. Multani, Takuma Makihara, Akasha G. Hayden, Ali Khalatpour, E. Alex Wollack, Antonia Akoto-Yeboah, Salva Salmani-Rezaie, Amir H. Safavi-Naeini
Lithium niobate (LN) is a promising material for building acoustic resonators used in quantum applications, but its performance is limited by poorly understood material defects called two-level systems (TLS). In this work, we fabricate high-performance acoustic resonators from LN with quality factors up to $6\times10^7$ and use them to separate bulk and surface contributions to TLS loss. By comparing these bulk acoustic wave (BAW) resonators with previous surface acoustic wave and phononic crystal studies, we show that devices with high surface participation ratios are limited by surface TLS, while our BAW devices reveal an intrinsic bulk TLS limit. Through systematic surface treatments and microscopy, we demonstrate that BAW resonator performance remains unchanged despite surface modifications, confirming operation in a bulk-limited regime. Our work establishes quantitative bounds on both surface and bulk TLS losses in LN, within the context of material growth and fabrication approaches we have pursued, and provides guidance for future device engineering and materials development.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Applied Physics (physics.app-ph), Quantum Physics (quant-ph)
13 pages, 11 figures
Non-Hermitian Effects in the Su-Schrieffer-Heeger model: Exploring Substrate Coupling and Decoupling Dynamics
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-01-15 20:00 EST
Shayan Edalatmanesh, Thomas Frederiksen
The substrate-adsorbate interaction can significantly influence the adsorbate’s electronic structure, stability, reactivity, and topological properties. In this study, we investigate the emergence of non-Hermitian physics in the Su-Schrieffer-Heeger (SSH) model when coupled to a substrate, focusing on the impact of substrate interaction on the electronic states of the adsorbate. We demonstrate how the coupling between the SSH chain and the underlying substrate induces non-Hermitian effects, which manifest as amplification or attenuation of zero-energy electronic states. Furthermore, inspired by novel experimental techniques such as using a scanning tunneling microscope tip to lift part of the nanomaterial, we present simulations of scenarios where a segment of the SSH chain is decoupled from the substrate. By examining various configurations, including cases with odd or even numbers of sites coupled to the substrate, we demonstrate that tuning the coupling strength induces novel phenomena, such as the emergence of a zero-energy monomode or additional zero-energy states localized at the boundary between on-surface and suspended chain segments. Our results reveal the role of substrate coupling in shaping the topological properties of non-Hermitian SSH chains, offering new insights into tunable non-Hermitian effects and their potential applications in quantum technologies and nanodevices.
Materials Science (cond-mat.mtrl-sci)
Two-Peak Heat Capacity Accounts for $R\ln(2)$ Entropy and Ground State Access in the Dipole-Octupole Pyrochlore Ce$_2$Hf$_2$O$_7$
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-01-15 20:00 EST
E. M. Smith, A. Fitterman, R. Schäfer, B. Placke, A. Woods, S. Lee, S. H.-Y. Huang, S. Sharma, J. Beare, D. Chatterjee, C. Balz, M. B. Stone, A. I. Kolesnikov, A. R. Wildes, P. Manuel, D. Khalyavin, E. Kermarrec, G. M. Luke, O. Benton, R. Moessner, R. Movshovich, A. D. Bianchi, B. D. Gaulin
We report new magnetic heat capacity measurements of a high quality single crystal of the dipole-octupole pyrochlore Ce$_2$Hf$_2$O$_7$ down to a temperature of $T = 0.02$ K, a factor of three lower than those previously reported. These show a two-peaked structure, with a Schottky-like peak at $T_1 \sim 0.065$ K, similar to what is observed in its sister Ce-pyrochlores Ce$_2$Zr$_2$O$_7$ and Ce$_2$Sn$_2$O$_7$. However a second, sharper peak is observed at $T_2 \sim 0.025$ K, which signifies the entrance to its ground state, as even the most abrupt low-temperature extrapolation to $C_P=0$ at $T = 0$ K gives a full accounting of $R\ln(2)$ in entropy, associated with the well isolated pseudospin-1/2 doublet for Ce$^{3+}$ in this environment. The ground state could be conventionally ordered, although theory predicts a much larger anomaly in $C_P$, at much higher temperatures than the measured $T_2$, for expectations from an all-in all-out ground state of the nearest-neighbor XYZ Hamiltonian for Ce$_2$Hf$_2$O$_7$. The sharp low-temperature peak could also signify a cross-over from a classical to a quantum spin liquid regime. The diffuse magnetic neutron scattering observed from Ce$_2$Hf$_2$O$_7$ at low temperatures between $T_2$ and $T_1$ resembles that observed from Ce$_2$Zr$_2$O$_7$, which is well established as a $\pi$-flux quantum spin ice.
Strongly Correlated Electrons (cond-mat.str-el)
Main Text (7 pages, 4 figures), Supplemental Material (17 pages, 18 figures)