1. Institute of Physical Science and Information Technology and Information Materials and Intelligent Sensing Laboratory of Anhui Province, Anhui University, Hefei 230601, China
2. University of Science and Technology of China, Hefei 230026, P. R. China
3. Key Laboratory of Materials Physics and Anhui Key Laboratory of Nanomaterials and Nanotechnology, Institute of Solid State Physics, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, P. R. China
4. High Magnetic Field Laboratory of Anhui Province, Chinese Academy of Sciences, Hefei 230031, China