1. National Laboratory of Solid State Microstructures, Collaborative Innovation Center of Advanced Microstructures, and School of Physics, Nanjing University, Nanjing 210093, China
2. Atomic Manufacture Institute (AMI), Nanjing 211805, China
3. School of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
4. High Magnetic Field Laboratory, Chinese Academy of Science, Hefei, 230031 Anhui, China