期刊
SCIENCE CHINA-PHYSICS MECHANICS & ASTRONOMY
卷 65, 期 8, 页码 -出版社
SCIENCE PRESS
DOI: 10.1007/s11433-022-1898-7
关键词
spin-orbit coupled ultracold atoms; exceptional loop; Wilson-loop method; non-Hermitian non-Abelian Berry curvature
资金
- national natural science foundation of china [11904109, 12074180, U1801661]
- guangdong basic and applied basic research foundation [2019AI51511110]
- science and technology program of guanghou [2019050001]
- key-area researc and development program of guandong provience [2019b030330001]
This study investigates the gain/loss effects on spin-orbit coupled ultracold atoms in two-dimensional optical lattices, revealing the interplay of non-Hermiticity and spin-orbit coupling. The researchers analytically obtain the topological phase diagram and develop a gauge-independent Wilson-loop method for numerically calculating the Chern number of multiple degenerate complex bands.
Due to the fundamental position of spin-orbit coupled ultracold atoms in the simulation of topological insulators, the gain/loss effects on these systems should be evaluated when considering the measurement or the coupling to the environment. Here, incorporating the mature gain/loss techniques into the experimentally realized spin-orbit coupled ultracold atoms in two-dimensional optical lattices, we investigate the corresponding non-Hermitian tight-binding model and evaluate the gain/loss effects on various properties of the system, revealing the interplay of the non-Hermiticity and the spin-orbit coupling. Under periodic boundary conditions, we analytically obtain the topological phase diagram, which undergoes a non-Hermitian gapless interval instead of a point that the Hermitian counterpart encounters for a topological phase transition. We also unveil that the band inversion is just a necessary but not sufficient condition for a topological phase in two-level spin-orbit coupled non-Hermitian systems. Because the nodal loops of the upper or lower two dressed bands of the Hermitian counterpart can be split into exceptional loops in this non-Hermitian model, a gauge-independent Wilson-loop method is developed for numerically calculating the Chern number of multiple degenerate complex bands. Under open boundary conditions, we find that the conventional bulk-boundary correspondence does not break down with only on-site gain/loss due to the lack of non-Hermitian skin effect, but the dissipation of chiral edge states depends on the boundary selection, which may be used in the control of edge-state dynamics. Given the technical accessibility of state-dependent atom loss, this model could be realized in current cold-atom experiments.
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