1. International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
2. Center for Polymer Studies and Department of Physics, Boston University, Boston, Massachusetts 02215, USA
3. Department of Physics, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA
4. Collaborative Innovation Center of Quantum Matter, Beijing, China
5. Department of Physics, Yeshiva University, 500 West 185th Street, New York, New York 10033, USA