1. Key Laboratory of Artificial Structures and Quantum Control (Ministry
of Education), School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 100140, China
2. Department of Physics, Zhejiang University, Hangzhou 310027, Zhejiang China
3. Collaborative
Innovation Center of Advanced Microstructures, Nanjing 210093, China
4. Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027, China