1. Department of Physics, Florida State University, Tallahassee, Florida 32306, United States
2. State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China
3. Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
4. Beijing Academy of Quantum Information Science, Beijing 100193, China