1. State Key Laboratory of Artificial Microstructure and Mesoscopic Physics; School of Physics; Peking University; Beijing 100871 P. R. China
2. King Abdullah University of Science and Technology; Division of Physical Science and Engineering; Thuwal 23955-6900 Kingdom of Saudi Arabia
3. Collaborative Innovation Center of Quantum Matter; Beijing 100871 P. R. China
4. Microsystem & Terahertz Research Center; China Academy of Engineering Physics (CAEP); Chengdu 610200 P. R. China