1. Wuhan National High Magnetic Field Center and School of Physics Huazhong University of Science and Technology Wuhan 430074 P. R. China
2. Institute for Advanced Materials South China Academy of Advanced Optoelectronics South China Normal University Guangzhou 510006 P. R. China
3. Jiangsu Key Laboratory of Thin Films School of Physical Science and Technology Soochow University Suzhou 215006 P. R. China
4. School of Physics Huazhong University of Science and Technology Wuhan 430074 P. R. China
5. State Key Laboratory of Materials Processing and Die & Mould Technology School of Materials Science and Engineering Huazhong University of Science and Technology Wuhan 430074 P. R. China
6. Guangdong Provincial Key Laboratory of Optical Information Materials and Technology South China Academy of Advanced Optoelectronics South China Normal University Guangzhou 510006 P. R. China
7. Laboratory of Solid State Microstructures and Innovation Center of Advanced Microstructures Nanjing University Nanjing 210093 P. R. China