1. State Key Laboratory for Mesoscopic Physics, School of Physics, Peking University, Beijing 100871, China
2. Nano-optoelectronics Frontier Center of Ministry of Education (NFC-MOE) & Collaborative Innovation Center of Quantum Matter, Peking University, Beijing 100871, China
3. Geballe Laboratory for Advanced Materials, Stanford University, Stanford, California 94305, United States
4. Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan, Shanxi 030006, China