1. State Key Laboratory of Tribology in Advanced Equipment (SKLT), Department of Mechanical Engineering, Tsinghua University, Beijing 100084, China
2. Center for Nano and Micro Mechanics, Tsinghua University, Beijing 100084, China
3. Samsung Research China − Beijing (SRC-B), Beijing 100102, China
4. Institute of Superlubricity Technology, Research Institute of Tsinghua University in Shenzhen, Shenzhen 518063, Guangdong, China