1. Graduate Program in Applied Physics, Northwestern University, Evanston, Illinois 60208, United States
2. Department of Materials Science, Northwestern University, Evanston, Illinois 60208, United States
3. Present: School of Mathematics and Physics, University of Science and Technology Beijing, Beijing 100083, China
4. Present: QuesTek Innovations LLC, Evanston, Illinois 60201, United States
5. Toyota Research Institute, Los Altos, California 94022, United States