Annalen der Physik最新文献

The interplay between Floquet periodically driving and non-Hermiticity could bring about intriguing novel phenomena with anomalous Floquet topological phases of a finite-size, tight-binding lattice model. How to efficiently investigate on quasi-energy and eigenstate distribution of a non-Hermitian Floquet system with complicated driving protocol remains a challenging task. In this work, we define a somewhat complex driving protocol for a bipartite lattice system for the investigation. Thereafter, we introduce unsupervised learning method in order to explore distribution features of system eigenfunctions under different magnitude of system energy gain/loss. An amortized clustering strategy is adopted to perform state classification. We further introduce an algorithm-selection mechanism that adapts to varying gain/loss strengths by choosing the most suitable clustering model based on unsupervised indices and task-oriented separability. Proper employment of the selector enables us to reveal the categories of eigenstate distribution from abundant possible wave function distribution in two-dimension lattice in another efficient way. In addition, our work provides a feasible methodology via machine Amortized Clustering, Periodically Driven non-Hermitian Lattice, nomalous Hybrid Floquet Modeslearning method to assist in classification of Floquet modes.

The pursuit of high-temperature superconductors at ambient pressure represents one of the foremost challenges in contemporary condensed matter physics, particularly within the realm of hydride materials. This review presents recent theoretical breakthroughs and experimental advances in binary/ternary hydrides and boron–carbon/boron–nitrogen clathrates, highlighting their emergence as candidates for superconductivity. We establish an analytical framework examining the critical relationship between hydrogen content, crystal structure, and electron–phonon coupling, illuminating how some ternary systems circumvent the extreme pressure requirements of their binary counterparts through chemical diversity and lattice stabilization. We introduce a new superconducting quality factor that serves as a metric correlating critical temperatures with stability pressures, providing a unified basis for comparative evaluation across material systems. Hydride superconductors achieve elevated transition temperatures through strong electron–phonon coupling facilitated by hydrogen atoms incorporated within metallic lattices or metallic host frameworks, though many require high pressures for stabilization. Boron–carbon/boron–nitrogen compounds serve as hydride substitutes, with clathrates offering exceptional tunability through their cage-like frameworks, while both systems potentially provide high-temperature superconductivity under more accessible conditions. We systematically address persistent challenges in thermodynamic stability and critical temperatures, ultimately aiming to accelerate the discovery of practically viable superconducting hydrides and clathrates by establishing clear structure-property relationships and identifying pathways for future investigation.

Vortex beams carrying orbital angular momentum (OAM) have garnered significant research interest due to their broad applications in areas such as optical communications and particle manipulation. However, progress in this field has been hindered by a fundamental constraint: the intrinsic coupling between topological charge and beam radius in conventional vortex beams. Perfect vortex beams (PVBs) offer a solution to this limitation by decoupling the topological charge from the radial extent of the beam. Moreover, metasurfaces—benefiting from their inherent integrability and flexibility—can employ various phase modulation mechanisms to replace traditional, bulky optical systems based on spiral phase plates, axicons, and Fourier lenses. This review outlines the fundamental principles for generating PVBs and categorizes different metasurface-based approaches. It highlights a synergistic innovation strategy that integrates multidimensional light-field control with device-level miniaturization. Through precise design of subwavelength structures, metasurfaces not only contribute to the miniaturization and weight reduction of optical systems, but also exhibit exceptional capabilities in phase manipulation across a wide spectral range, from visible to terahertz frequencies.

The negatively charged nitrogen-vacancy (NV) center in diamond is a leading solid-state quantum emitter, offering spin-photon interfaces over a wide temperature range with applications from electromagnetic sensing to bioimaging. While NV centers in bulk diamond are well understood, embedding them in nanodiamond (ND) introduces complexities from size, NV location, and NV polarizations. NVs in ND show altered fluorescence properties, including longer lifetimes, lower quantum efficiency, and higher sensitivity to dielectric surroundings, which arise from radiative suppression, surface-induced non-radiative decay, and escape inefficiency at the diamond-background interface. Prior models typically addressed isolated aspects, such as dielectric contrast or surface quenching, without integrating full quantum-optical NV behavior with classical electrodynamics. We present a hybrid framework coupling rigorous electromagnetic simulations with a quantum-optical NV model including phonon sideband dynamics. NV emission is found to depend strongly on ND size, NV position, and surrounding refractive index. Our results explain observations such as shallow NVs in water-coated ND appearing brighter than deeper ones in air. This integrated model provides a unified framework for realistic NV in ND emission scenarios and informs the design of efficient NV-based sensors and quantum devices, advancing understanding of quantum emitter photophysics in nanoscale crystals.

Topologically protected systems are characterized by robust boundary states immune to perturbations. Herein, we propose and analyze a tripartite scheme for simulating topological edge states with silicon-vacancy (SiV) center arrays in 1D phononic crystals. We first investigate the pattern of trimer interactions extended from the standard Su-Schrieffer-Heeger (SSH) model. In momentum space, the results indicate that this structure exhibits unique topological properties, including specific symmetries and multiple types of boundary state configurations. Among them, depending on the hopping integrals, the system harbors both symmetry-protected edge states and topologically trivial edge states. Moving to the realistic quantum system, we introduce a periodic driving protocol for mapping the trimerized spin interactions in 1D phononic crystals (PnCs). Based on the bandgap engineered spin-phonon coupling, after adiabatic elimination of the phonon modes, we derive the highly tunable long-range spin interactions. Thus, by means of a specially designed on-site potential with periodic driving, one can selectively control and enhance the spin-spin interactions, thereby achieving trimerized interaction in SiV center arrays. We show that, the effective Floquet Hamiltonian combines the inversion and time-reversal (TR) symmetries, and then numerically simulate the topologically protected edge states with various periodic driving parameters. This work provides a tunable platform to engineer nontrivial topological states of matter in solid-state quantum systems.

Electromagnetic metamaterials can regulate the propagation behavior of electromagnetic waves through the distribution of effective refractive indices. Two kinds of self-adaptive electromagnetic metamaterials whose electromagnetic properties can be changed automatically under mechanical deformation are designed in this research. When the two kinds of metamaterials undergo bending or shear deformation, respectively, electromagnetic waves propagating in them will also propagate in a bent or sheared path, respectively. The metamaterials are designed to be a combination of an effective electromagnetic medium, which is realized using dielectric arrays, and a mechanical structure, which is realized using a mechanical metamaterial or a link mechanism. The self-adaptive conditions of the two kinds of metamaterials are derived based on transformation optics theory, and the structural parameters of the metamaterials are determined with the help of computer simulation. The self-adaptivity of the metamaterials is verified through full wave simulation. The self-adaptive metamaterials designed in this study are passive with no need for external sensors or power source, and the non-resonant feature of the metamaterial structures enables a broad band operating frequency. This research may be helpful for the future applications of metamaterials in complex environments.

We present our studies on intra-trap dynamics of an optical dipole trap loaded from a Magneto-optical trap of $��{}^{87}�\mathrm{Rb}�$ atoms. A spatio-temporal Monte Carlo simulation approach has been employed in conjunction with the semi-classical theory based calculations for the estimation of various intra-trap two-body loss parameters in the optical dipole trap. Our methodology gives a close estimation of the experimentally observed the atom-number evolution in the optical dipole trap. We also find that, the decay rate of atoms in an optical dipole trap is dominated by momentum-transfer elastic collisions due to the absence of Magneto-optical trap beams. However, in presence of Magneto-optical trap beams, the radiative escape process is the dominant two-body loss mechanism in the trap, which surpasses the fine-structure changing and hyperfine changing collisional losses by nearly an order of magnitude.