1. Department of Physics, Columbia University, New York, New York 10027, United States
2. Department of Chemistry, Columbia University, New York, New York 10027, United States
3. Department of Mechanical Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States
4. Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027, United States
5. National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-0044 Japan
6. Laboratoire MOLTECH, CNRS UMR 6200, Université d’Angers, 49045 Angers, France