1. State Key Laboratory for Mesoscopic Physics and Department of Physics; Peking University; Beijing 100871 P. R. China
2. University of Colorado; Boulder Colorado 80309 USA
3. Academy for Advanced Interdisciplinary Studies; Peking University; Beijing 100871 P. R. China
4. School of Advanced Materials; Peking University, Shenzhen Graduate School; Shenzhen 518055 P. R. China
5. Collaborative Innovation Center of Quantum Matter; Beijing 100871 P. R. China
6. Department of Nuclear Science and Engineering and Department of Materials Science and Engineering; Massachusetts Institute of Technology; Cambridge Massachusetts 02139 USA