1. Department of Physics, University of Southern California, Los Angeles, CA 90089-0484, USA
2. Department of Physics, Fu Jen Catholic University, Taipei 242, Taiwan
3. School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China
4. Institute of Applied Physics and Computational Mathematics, Beijing 100088, China
5. Faculty of Science, Kunming University of Science and Technology, Kunming 650500, China
6. National Key Laboratory of Computational Physics, Beijing 100088, China