1. Key Laboratory of Environmental Optics and Technology, and Institute of Solid State Physics, Hefei Institute of Physical Science, Chinese Academy of Sciences, Hefei, Anhui 230031, P. R. China
2. University of Science and Technology of China, Hefei, Anhui 230031, P. R. China
3. High Magnetic Field Laboratory, CAS Key Laboratory of High Magnetic Field and Ion Beam Physical Biology, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei, Anhui, 230031, P. R. China
4. Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Hefei 230031, P. R. China