1. Key Laboratory for the Physics and Chemistry of Nanodevices, School of Electronics, Peking University, Beijing 100871, China
2. Institute of Spin Science and Technology, South China University of Technology, Guangzhou 511442, China
3. Centre for Nanoscale Science and Technology, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing 100871, China
4. School of Physics, AMBER and CRANN Institute, Trinity College, Dublin 2, Ireland