1. Laboratory of Atomic and Solid State Physics, Cornell University, Ithaca, New York 14853, United States
2. Geballe Laboratory for Advanced Materials, Stanford University, Stanford, California 94305, United States
3. State Key Lab of New Ceramics and Fine Processing, School of Materials Science and Engineering, Tsinghua University, Beijing 100084, China
4. Department of Applied Physics, Stanford University, Stanford, California 94305, United States
5. School of Integrated Circuits and Beijing National Research Center for Information Science and Technology (BNRist), Tsinghua University, Beijing 100084, China
6. Laboratory of Atomic and Solid-State Physics, Cornell University, Ithaca, New York 14853, United States
7. Kavli Institute at Cornell for Nanoscale Science, Ithaca, New York 14853, United States