1. National Laboratory of Solid State Microstructures and Jiangsu Provincial Key Laboratory of Advanced Photonic and Electronic MaterialsSchool of Electronic Science and EngineeringNanjing University Nanjing 210023 China
2. State Key Laboratory of Infrared PhysicsShanghai Institute of Technical PhysicsChinese Academy of Sciences 500 Yutian Road Shanghai 200083 China
3. Key Laboratory of Optical Communication Science and Technology of Shandong Province School of Physical Science and Information EngineeringLiaocheng University Liaocheng 252059 China
4. National Laboratory of Solid State MicrostructuresCollege of Engineering and Applied Sciences and Collaborative Innovation Center of Advanced MicrostructuresNanjing University Nanjing 210023 China
5. Department of Electronic EngineeringRoyal HollowayUniversity of London Egham Surrey TW20 0EX UK
6. York‐Nanjing Joint Center in SpintronicsDepartment of Electronic Engineering and Department of PhysicsThe University of York York YO10 5DD UK