1. Department of Physics, National Tsing Hua University, Hsinchu 30013, Taiwan
2. Department of Physics, National Central University, Jhongli 32001, Taiwan
3. Department of Physics, Tamkang University, Tamsui Dist., New Taipei City 25137, Taiwan
4. Frontier Research Center on Fundamental and Applied Sciences of Matters, National Tsing Hua University, Hsinchu 30013, Taiwan