1. Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100080, China, Department of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083, China, Department of Physics, National University of Singapore, Singapore 117542, Singapore, International Center for Materials Physics, Chinese Academy of Sciences, Shenyang 110016, China, and Division of Physics and Applied Physics, School of Physical and...