1. Institute for Advanced Materials and Guangdong Provincial Key Laboratory
of Quantum Engineering and Quantum Materials, South China Normal University, Guangzhou 510006, China
2. Department of Materials Science and Engineering, University of California, Berkeley, Berkeley, California 94720, United States
3. School of Materials Science and Engineering, South China University of Technology, Guangzhou 510640, China
4. Department of Physics, University of California Berkeley, Berkeley, California 94720, United States
5. Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
6. Department
of Electrical Engineering and Computer Sciences, University of California Berkeley, Berkeley, California 94720, United States
7. School
of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan 430074, China
8. Department
of Physics, South University of Science and Technology of China, Shenzhen 518055, China
9. Laboratory of Solid State Microstructures and Innovation Center of
Advanced Microstructures, Nanjing University, Nanjing 210093, China