Qing-Rui Wang, 2 Yang Qi, 4 Chen Fang, Meng Cheng, and Zheng-Cheng Gu Yau Mathematical Sciences Center, Tsinghua University, Haidian, Beijing 100084, China Yanqi Lake Beijing Institute of Mathematical Sciences and Applications, Huairou, Beijing 101408, China Center for Field Theory and Particle Physics, Department of Physics, Fudan University, Shanghai 200433, China State Key Laboratory of Surface Physics, Fudan University, Shanghai 200433, China Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China Department of Physics, Yale University, New Haven, CT 06511-8499, USA Department of Physics, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China