1. Key Laboratory of Materials PhysicsInstitute of Solid State PhysicsChinese Academy of Sciences Hefei 230031 P. R. China
2. Department of PhysicsSouthern University of Science and Technology Shenzhen 518055 P. R. China
3. Department of PhysicsJiangsu University of Science and Technology Zhenjiang 212003 P. R. China
4. High Magnetic Field LaboratoryChinese Academy of Sciences Hefei 230031 P. R. China
5. Collaborative Innovation Centre of Advanced MicrostructuresNanjing University Nanjing 210093 P. R. China