1. State Key Laboratory for Artificial Microstructure and Mesoscopic Physics and School of Physics Peking University Beijing 100871 P. R. China
2. National Institute for Materials Science 1‐1 Namiki Tsukuba 305‐0044 Japan
3. Collaborative Innovation Center of Quantum Matter Beijing 100871 P. R. China
4. Frontiers Science Center for Nano‐optoelectronics Peking University Beijing 100871 P. R. China
5. Beijing Key Laboratory for Magnetoelectric Materials and Devices Beijing 100871 P. R. China