1. NanoLund & Department of Physics, Lund University, Box 118, 22100 Lund, Sweden
2. Department of Physics and Astronomy, Materials Theory, Box 516, 751 20 Uppsala, Sweden
3. State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, P.O. Box 912, Beijing 100083, China
4. Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100190, China
5. Beijing Key Laboratory of Quantum Devices, Key Laboratory for the Physics and Chemistry of Nanodevices and Department of Electronics, Peking University, Beijing 100871, China
6. Beijing Academy of Quantum Information Sciences, Beijing 100193, China