1. University of Washington, Physics Department, Seattle, Washington 98105, United States
2. University of Washington, Electrical and Computer Engineering Department, Seattle, Washington 98105, United States
3. Princeton University, Electrical and Computer Engineering Department, Princeton, New Jersey 08544, United States
4. Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, Singapore 138634, Singapore
5. Department of Physics, Humboldt-Universitat zu Berlin, Newtonstrasse, Berlin, 10117, Germany
6. Physical Sciences Division, Pacific Northwest National Laboratory, Richland, Washington 99352, United States