1. State Key Laboratory for Mesoscopic Physics and Department of PhysicsPeking University Beijing 100871 P. R. China
2. State Key Laboratory of Information Photonics and Optical Communications and School of ScienceBeijing University of Posts and Telecommunications Beijing 100876 P. R. China
3. Beijing Key Laboratory for Magnetoelectric Materials and DevicesPeking University Beijing 100871 P. R. China
4. School of Physics and Electronic Information EngineeringEngineering Research Center of Nanostructure and Functional MaterialsNingxia Normal University Guyuan Ningxia 756000 P. R. China
5. Key Laboratory for the Physics and Chemistry of Nanodevices and Department of ElectronicsPeking University Beijing 100871 P. R. China
6. Collaborative Innovation Center of Quantum Matter Beijing 100871 P. R. China