1. State Key Laboratory for Artificial Microstructure and Mesoscopic Physics; Department of Physics; Peking University; Beijing 100871 China
2. Collaborative Innovation Center of Quantum Matter; Beijing 100871 China
3. Materials Sciences Division; Lawrence Berkeley National Laboratory; CA 94720 USA
4. School of Chemistry; Joseph Banks Laboratories; University of Lincoln; Beevor Street Lincoln LN6 7DL UK
5. Advanced Technology Institute; University of Surrey; Guildford GU2 7XH UK
6. Collaborative Innovation Center of Extreme Optics; Shanxi University; Taiyuan Shanxi 030006 China