Affiliation: | [1]Lab of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093, China; [2]Jiangsu Key Laboratory for Chemistry of Low-Dimensional Materials and Department of Physics, Huaiyin Normal University, Huaian 223300, China; [3]BSRF, Institute of High Energy Physics, CAS, Beijing 100049, China |