Xixiang Zhang1, Bei Zhang1, Shuyun Yu2, Zhuhong Liu2, Wenjin Xu1, Guodong Liu2, Jinglan Chen2, Zexian Cao2, Guangheng Wu2
1Department of Physics, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, People’s Republic of China
2Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100080, China