arXiv subjects

Xin-Yu Guo

Publications and source records attributed to Xin-Yu Guo.

4 recordsLinked to original sources

arXiv2026

Charged Black Holes with a Lorentz--Violating Kalb--Ramond Background

We investigate exact static, spherically symmetric electrically charged black hole solutions in a gravitational theory with spontaneous Lorentz-symmetry breaking induced by a background Kalb--Ramond field. In contrast to previous analyses that retained only one nonminimal curvature coupling, we include the combined effects of the two independent nonminimal curvature couplings and obtain charged black hole solutions both with and without a cosmological constant. Using the Iyer--Wald covariant phase-space formalism, we derive the corrected thermodynamic quantities and analyze the Joule--Thomson expansion, including the inversion curve and the cooling/heating regions. We further apply the topological approach to black hole thermodynamics to characterize the van der Waals-like phase transition and show how the thermodynamic critical temperature and pressure are encoded in the corresponding topological defect curve. These results clarify the thermodynamic and topological signatures of electrically charged black holes in gravity with a Lorentz-violating Kalb--Ramond background.

gr-qc↗

arXiv2025

Theory of Localized States in Quasiperiodic Lattices

The physics of localized states in quasiperiodic lattices has been extensively studied for decades, but still lacks an comprehensive theoretical framework. Recently, we developed a incommensurate energy band (IEB) theory, which extends the concept of energy bands to quasiperiodic systems lacking translational symmetry, thereby achieving a breakthrough in elucidating extended states. Here, we demonstrate that, due to the inherent duality between momentum and real space, the IEB theory also offers a comprehensive framework for elucidating localized states. Specifically, via a so-called spiral (module) mapping, the energy spectrum of localized states can be represented as a function defined on a compact circular manifold-akin to the Brillouin zone-whose form resembles conventional energy bands. These localized state energy bands (LSEBs) fully characterize all the properties of the localized states. Moreover, we show that quasiperiodic systems with mobility edges exhibit a unique hybrid band structure: the IEB for extended states (momentum space) and LSEB for localized states (real space), separated by mobility edges. Our theory thus establishes a comprehensive framework for analyzing the localized states in quasiperiodic lattices.

cond-mat.dis-nn↗

arXiv2024

Energy Bands of Incommensurate Systems

Energy band theory is a fundamental cornerstone of condensed matter physics. According to conventional wisdom, discrete translational symmetry is mandatory for defining energy bands. Here, we illustrate that, in fact, the concept of energy band can be generalized to incommensurate systems lacking such symmetry, thus transcending the traditional paradigm of energy band. The validity of our theory is verified by extensive numerical calculations in the celebrated Aubry-André-Harper model and a two-dimensional incommensurate model of graphene. Building upon the proposed concept of incommensurate energy bands, we further develop a theory of angle-resolved photoemission spectroscopy (ARPES) for incommensurate systems, providing a clear physical picture for the incommensurate ARPES spectra. Our work establishes a comprehensive energy band theory for incommensurate systems.

cond-mat.mes-hall↗

arXiv2023

Energy Spectrum Theory of Incommensurate Systems

Due to the lack of the translational symmetry, calculating the energy spectrum of an incommensurate system has always been a theoretical challenge. Here, we propose a natural approach to generalize the energy band theory to the incommensurate systems without reliance on the commensurate approximation, thus providing a comprehensive energy spectrum theory of the incommensurate systems. Except for a truncation dependent weighting factor, the formulae of this theory are formally almost identical to that of the Bloch electrons, making it particularly suitable for complex incommensurate structures. To illustrate the application of this theory, we give three typical examples: one-dimensional bichromatic and trichromatic incommensurate potential model, as well as a moiré quasicrystal. Our theory establishes a fundamental framework for understanding the incommensurate systems.

cond-mat.mes-hall↗