1. Key Laboratory of Artificial Structures and Quantum Control and Shanghai Center for Complex Physics, School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China
2. Department of Physics, Tulane University, New Orleans, Louisiana 70118, USA
3. Collaborative Innovation Center of Advanced Microstructures, Nanjing 210093, China
4. Department of Physics and Materials Research Institute, Pennsylvania State University, University Park, Pennsylvania 16802, USA