Gain/loss effects on spin-orbit coupled ultracold atoms in two-dimensional optical lattices  

作　　者：Zhi-Cong Xu Ziyu Zhou Enhong Cheng Li-Jun Lang Shi-Liang Zhu 

机构地区：[1]Guangdong Provincial Key Laboratory of Quantum Engineering and Quantum Materials,School of Physics and Telecommunication Engineering,South China Normal University,Guangzhou,510006,China [2]Guangdong-Hong Kong Joint Laboratory of Quantum Matter,Frontier Research Institute for Physics,South China Normal University,Guangzhou,510006,China

出　　处：《Science China(Physics,Mechanics & Astronomy)》2022年第8期85-95,共11页中国科学：物理学、力学、天文学（英文版）

基　　金：supported by the National Natural Science Foundation of China(Grant No.11904109);the Guangdong Basic and Applied Basic Research Foundation(Grant No.2019A1515111101);the Science and Technology Program of Guangzhou(Grant No.2019050001);supported by the Key-Area Research and Development Program of Guangdong Province(Grant No.2019B030330001);the National Natural Science Foundation of China(Grant Nos.12074180,and U1801661)。

摘　　要：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.

关 键 词：spin-orbit coupled ultracold atoms exceptional loop Wilson-loop method non-Hermitian non-Abelian Berry curvature 

分 类 号：O469[理学—凝聚态物理]