1. Department of Applied Physics, Yale University, New Haven, Connecticut 06520, USA
2. Department of Physics, Yale University, New Haven, Connecticut 06520, USA
3. Department of Mechanical Engineering and Materials Science, Yale University, New Haven, Connecticut 06520, USA
4. Center for Research on Interface Structure and Phenomena, Yale University, New Haven, Connecticut 06520, USA
5. Department of Physics and Astronomy, Rutgers University, Piscataway, New Jersey 08854, USA
6. Rutgers Center for Emergent Materials, Rutgers University, Piscataway, New Jersey 08854, USA