1. Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan
2. Department of Materials Science and Engineering, National Chiao Tung University, Hsinchu 30010, Taiwan
3. School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083, China
4. Department of Physics, National Cheng Kung University, Tainan 70101, Taiwan
5. Center for Theoretical Physics, Department of Physics, Faculty of Science, University of Malaya, Kuala Lumpur 50603, Malaysia
6. Department of Mechanical Engineering, Ming Chi University of Technology, New Taipei City 24301, Taiwan