Affiliation: | 1. Department of Physics, School of Mathematics and Physics, University of Science and Technology Beijing, Beijing 100083, PR China;2. Department of Applied Physics, Chongqing University, Chongqing 400044, PR China;3. Department of Physics, COMSATS Institute of Information Technology, Lahore 54000, Pakistan;4. Department of Physics, Khwaja Freed University of Engineering and Information Technology, Rahim Yar-Khan 64200, Pakistan |