1. Laboratory for Topological Quantum Matter and Spectroscopy (B7), Department of Physics, Princeton University, Princeton, NJ 08544, USA.
2. International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China.
3. Centre for Advanced 2D Materials and Graphene Research Centre, National University of Singapore, 6 Science Drive 2, Singapore 117546, Singapore.
4. Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542, Singapore.
5. Department of Physics, National Tsing Hua University, Hsinchu 30013, Taiwan.
6. Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland.
7. Center for Condensed Matter Sciences, National Taiwan University, Taipei 10617, Taiwan.
8. Institute of Physics, Academia Sinica, Nankang, Taipei 11529, Taiwan.
9. Department of Physics, Northeastern University, Boston, MA 02115, USA.
10. Princeton Center for Theoretical Science, Princeton University, Princeton, NJ 08544, USA.
11. Collaborative Innovation Center of Quantum Matter, Beijing 100871, China.
12. Princeton Center for Complex Materials, Princeton Institute for the Science and Technology of Materials, Princeton University, Princeton, NJ 08544, USA.