1. Department of Physics and Astronomy, Johns Hopkins University 1 , Baltimore, Maryland 21218, USA
2. Key Laboratory of Quantum Materials and Devices of Ministry of Education, School of Physics, Southeast University 2 , Nanjing 211189, China
3. Department of Mechanical Engineering, University of Texas at Austin 3 , Austin, Texas 78712, USA
4. Center for Condensed Matter Sciences, National Taiwan University 4 , Taipei 10617, Taiwan
5. Department of Physics, National Taiwan University 5 , Taipei 10617, Taiwan