The topology of quantum systems has become a topic of great interest since the discovery of topological insulators. However, as a hallmark of the topological insulators, the spin Chern number has not yet been experimentally detected. The challenge to directly measure this topological invariant lies in the fact that this spin Chern number is defined based on artificially constructed wave functions. Here we experimentally mimic the celebrated Bernevig-Hughes-Zhang model with cold atoms, and then measure the spin Chern number with the linear response theory. We observe that, although the Chern number for each spin component is ill defined, the spin Chern number measured by their difference is still well defined when both energy and spin gaps are nonvanished.

• Received 28 April 2021              Accepted 12 August 2021

DOI:https://doi.org/10.1103/PhysRevLett.127.136802

AUTHORS & AFFILIATIONS

Qing-Xian Lv1,2, Yan-Xiong Du1,*, Zhen-Tao Liang1, Hong-Zhi Liu1, Jia-Hao Liang1, Lin-Qing Chen1, Li-Ming Zhou1, Shan-Chao Zhang1,2, Dan-Wei Zhang1,2, Bao-Quan Ai1,2, Hui Yan1,2,†, and Shi-Liang Zhu1,2,‡

• 1Guangdong Provincial Key Laboratory of Quantum Engineering and Quantum Materials, School of Physics and Telecommunication Engineering, South China Normal University, Guangzhou 510006, China

• 2Guangdong-Hong Kong Joint Laboratory of Quantum Matter, Frontier Research Institute for Physics, South China Normal University, Guangzhou 510006, China

• *yanxiongdu@m.scnu.edu.cn

• †yanhui@scnu.edu.cn

• ‡slzhu@scnu.edu.cn