1. State Key Laboratory of Low‐Dimensional Quantum Physics and Collaborative Innovation Center of Quantum Matter Department of Physics Tsinghua University Beijing 100084 China
2. Physics Department and Institute for Nanoscience and Engineering University of Arkansas Fayetteville AR 72701 USA
3. Materials Research and Technology Department Luxembourg Institute of Science and Technology Avenue des Hauts‐Fourneaux 5 L‐4362 Esch/Alzette Luxembourg
4. Institute for Advanced Study Tsinghua University Beijing 100084 China