1. School
of Physical Science and Technology and Key Laboratory
of Luminescent and Real-Time Analytical Chemistry, Ministry of Education, Southwest University, Chongqing 400715, China
2. State
Key Laboratory of Rare Earth Resource Utilization, Changchun Institute
of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, China
3. School
of Physics, Nanjing University and National Lab of Solid State Microstructure, Nanjing 210093, China
4. Department
of Physics, Tsinghua University, Beijing 100084, China