1. Institute of Atomic and Molecular Physics, Sichuan University, Chengdu 610065, China, and International Centre for Materials Physics, Academia Sinica, Shenyang 110016, China
2. CCAST (World Laboratory), P.O. Box 8730, Beijing 100080, China, Department of Physics, Sichuan University, Chengdu 610065, China, and International Centre for Materials Physics, Academia Sinica, Shenyang 110016, China