Annalen der Physik最新文献

The B₁₂ icosahedron serves as the fundamental building block in boron-rich compounds, where the combination of strong multi-center covalent bonding and low atomic mass favors high-frequency phonons and robust electron-phonon coupling, rendering them as promising candidates for high-temperature superconductivity. However, these materials are typically insulating due to the electron-counting rule. Here, we propose a viable strategy to achieve superconductivity in LiB₁₃C₂ by degassing Li and leading to the formation of icosahedron-based B₁₃C₂ superconductor. First-principles calculations demonstrate that the removal of Li alters density of states at the Fermi level ($�N_{E_F}$) while retains its 3D covalent framework. Strikingly, after the complete removal of Li, the resulting B₁₃C₂ is predicted to be an anisotropic single-gap superconductor with a critical temperature (T_c) of 53 K, primarily driven by strong coupling between B₁₂ icosahedral vibrational modes and conduction electrons. This work illustrates a potential route toward achieving high-temperature superconductivity in icosahedron-based boron-rich frameworks.

The susceptibility of second-harmonic generation (SHG) is highly dependent on the symmetry of the material. Constructing a Janus structure by surface modification can break out-of-plane mirror symmetry, leading to asymmetric charge distribution and the generation of a built-in electric field. This study systematically investigates the electronic properties and nonlinear optical responses of Janus derivative of graphane, by one side, fluorinating graphane. Due to the vertical built-in electric field, the out-of-plane SHG response is approximately three times that of the in-plane response, reaching around 60 pm/V. Through the intensity polar plots of the Janus monolayer under different incident lights, the anisotropic response of SHG is further Analyses. This research provides theoretical guidance for further experimental exploration of Janus fluorinated graphane and lays a foundation for its application in nonlinear optical devices.

The high critical temperature (high-T_c) hydride superconductor H₃S has attracted great interest in high-pressure superconductivity research. Finding a strategy to reduce its stabilization pressure while maintaining its high T_c is of great importance for hydrogen-based superconductor studies. In this work, we performed high-throughput calculations for $���F�d��\overline{3}�m�$-H₆SX, P3m1-H₉S₂X and $��P�\overline{3}��m�1��$-H₉S₂X at chosen pressures, where X corresponds to elements from groups IIIA to VIIA. Our results reveal that the difference in covalent radius between S and X atoms is a critical factor influencing the dynamically stable pressure and superconductivity of H₃S. The larger the covalent radius of X relative to S, the lower the dynamically stable pressure required for these hydrides, while still maintaining excellent superconductivity. Based on our analysis, we find that H₉S₂In, H₉S₂Sn, H₉S₂Te, and H₆SIn remain dynamically stable at 20 GPa, with T_c of 54, 72, 5, and 54 K, respectively. Our study proposes a novel strategy of introducing elements with large covalent radii into cubic H₃S to obtain high-T_c superconductors at mild pressure.

The quest for high-temperature superconductivity has recently been revolutionized by high-pressure hydrides, such as H₃S and LaH₁₀, however, their practical potential is limited by the extreme stabilization pressures. Ternary hydrides have emerged as a promising avenue to mitigate this pressure constraint and further enhance their superconducting properties. The increased compositional complexity in ternary ones offers greater structural versatility and tunability, leading to successful syntheses of compounds like La–Ce–H system and Lu–Y–H system at significantly lower pressures. This review comprehensively surveys the experimental advances in ternary hydride superconductors, highlighting recent discoveries across different structural families. Nevertheless, research in this domain faces substantial challenges, including synthetic inhomogeneity, complex phase diagrams, and difficulties in precise structural determination of hydrogen sublattices. This review also outlines future research trajectories, high pressure, conventional superconductivity, electron-phonon coupling, superconductor, ternary hydridesaimed at achieving high-temperature superconductivity under more practical conditions.

A hidden variables (HVs) model is reported, which reproduces quantum predictions for Bell-Clauser-Horne-Shimony-Holt (Bell-CHSH) tests. The existence of such a model poses some limitations to quantum certifications that rely on Bell-CHSH inequality violations. The reported model does not prove wrong Bell's theorem. The latter assumes the factorability of the probability density p_AB, which rules the stochastic behavior of the HVs. The reported HVs model is based on an extended form of p_AB, which is suggested by Lebesgue's decomposition theorem for bounded functions. The considered p_AB complies with locality and realism, and also with measurement independence, parameter independence and outcome independence.

In this study, we investigate the emergence of non-trivial topological phases in a 1D spin-1/2 XX model induced by anisotropic four-spin interactions. By employing the fermionization technique, we precisely diagonalize the system's Hamiltonian and analytically identify three critical lines. Subsequently, we calculate the energy gap, fidelity susceptibility, cluster local order parameters, winding number, and entanglement spectrum. Our findings identify three crucial boundaries that divide five gapped phases, each characterized by the coexistence of symmetry-protected topological order and spontaneous symmetry breaking. Analyzing the winding number as a topological invariant allows us to distinguish these gapped phases as distinct non-trivial topological phases, characterized by integer values of $��\nu �=�\pm �3�,�\pm �1�$. Moreover, we observe topological phase transitions at quantum critical points, where the winding number changes are associated with the closing and reopening of the energy gap. Furthermore, we demonstrate that for a given winding number $�\nu$, the degeneracy of the lowest eigenvalue in the entanglement spectrum is generally $��2�\left|�\nu �\right|�$. This work provides novel insights into the role of anisotropic four-spin interactions in driving topological phenomena in low-dimensional quantum systems, offering a deeper understanding of the interplay between topology and quantum fluctuations.

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.