Newsfeeds

New Journal of Physics - latest papers

Latest articles for New Journal of Physics

IOPscience

  • Spin-based true random number generation enabled by voltage-amplified quantum fluctuations
    We investigate spin quantum-fluctuation effects that originate from the Heisenberg uncertainty principle during the dynamical cycle of disentanglement, entanglement, and re-disentanglement between itinerant electrons and localized magnetic moments mediated by the s–d exchange interaction. Beyond conventional deterministic spin-transfer torque, we analyze an intrinsic mechanism that transfers spin quantum fluctuations to a nanomagnet. By extending the Landau–Lifshitz–Gilbert equation to incorporate both quantum and thermal stochastic fields, we identify a temperature regime in which quantum fluctuations dominate the magnetization dynamics. We further show that voltage-controlled magnetic anisotropy exponentially amplifies spin quantum fluctuations, enabling binary readout through magnetoresistance in magnetic tunnel junctions. These findings provide a microscopic framework for fluctuation-driven spin dynamics and outline a device-level pathway toward spin-based quantum true random number generation.

  • Competing magnetic order in EuPd 3 ...
    Single crystals of EuPd Si were grown using a high-temperature EuPd-flux method. The material was structurally and chemically characterized by single-crystal x-ray diffraction, powder x-ray diffraction, Laue method and energy-dispersive x-ray spectroscopy. The structural analysis confirmed the orthorhombic crystal structure (space group ) but revealed differences in the lattice parameters and bond distances. The composition is close to the ideal 1:3:2 stoichiometry with an occupation of 7% of the Si sites by Pd. The heat capacity, electrical resistivity, and magnetic susceptibility show two magnetic transitions indicating magnetic ordering below 61 K and a spin reorientation at 40 K. The orthorhombic material shows magnetic anisotropy, with anisotropy constants and , for field applied along the three main symmetry axes, which is summarized in the temperature-field phase diagrams. The susceptibility data hint to an alignment of the magnetic moments along between and . Below the magnetic structure changes to an arrangement with moments canted away from . The single crystals investigated in this study are suggested to show antiferromagnetic order below instead of ferromagnetism that sets in at higher which might originate from certain differences in the structure, composition or defects that have an impact on the dominant coupling constants of the Ruderman–Kittel–Kasuya–Yosida interaction.

  • Excitons in 2H-MoTe2: anisotropies, masses and binding energy
    Bound electron–hole pairs called excitons determine the photophysical behavior of semiconducting materials. In this study, we present a combination of electron energy-loss spectroscopy in transmission and optical absorption spectroscopy for the investigation of excitons in bulk 2H-MoTe2. The exciton dispersion E(q) was measured for momentum transfers oriented along the ΓK and ΓM directions at 20 K. From the extracted dispersion relations, the in-plane exciton effective mass was determined. Our results reveal that for 2H-MoTe2 the exciton effective mass is anisotropic. In consideration of the complementary optical results the exciton reduced mass, binding energy and radius have been determined.

  • Sparse identification of quantum Hamiltonian dynamics via quantum circuit learning
    Sparse identification of nonlinear dynamics (SINDy) is a data-driven framework for estimating classical nonlinear dynamical systems from time-series data. In this approach, system dynamics is represented as a linear combination of a predefined set of basis functions, and the corresponding coefficients are sparsely estimated from observed time-series data. In this study, we propose sparse identification of quantum Hamiltonian dynamics (SIQHDy), a SINDy-inspired quantum circuit learning framework for estimating quantum Hamiltonian dynamics from time-series data of quantum measurement outcomes. In SIQHDy, the unitary evolution of a quantum Hamiltonian system is expressed as a product of basis quantum circuits, and the corresponding circuit parameters are estimated through sparsity-promoting optimization. We numerically demonstrate that SIQHDy accurately reconstructs the dynamics of single-, three-, and five-spin systems, and exhibits robustness to measurement noise in the three-spin case. Furthermore, we propose an extension of SIQHDy for scenarios with limited accessible observables and evaluate its performance in identifying three-spin systems and in network-structure identification for five-spin systems.

  • Low-dimensional dynamical behavior of locally coupled chiral swarmalators
    Understanding the dynamical behavior of swarmalators, particularly the transition from disorder to synchronization, constitutes one of the pivotal frontiers in the study of complex systems. We propose an ansatz that successfully decouples the spatial and phase dynamics in the locally coupled chiral swarmalators model, enabling rigorous analytical treatment of this complex system. Within this framework, we systematically examine how the interaction radius affects system synchronization, quantified through an order parameter measuring phase coherence. Our theoretical analysis reveals that increasing the interaction radius enhances synchronization in both velocity and phase dynamics. This relationship demonstrates that larger interaction networks facilitate more efficient information transfer among heterogeneous oscillators with different intrinsic frequencies. Using a self-consistent approach in the thermodynamic limit, we derive analytical expressions for the order parameter that accurately predict the synchronization transition. These findings provide fundamental insights into synchronization mechanisms in spatially embedded swarmalator systems with applications in understanding biological collective behaviors.