1. Laboratory of Atomic and Solid-State Physics, Cornell University, Ithaca, NY 14853, USA.
2. Sibley School of Mechanical and Aerospace Engineering, Cornell University, Ithaca, NY 14853, USA.
3. School of Applied and Engineering Physics, Cornell University, Ithaca, NY 14853, USA.
4. Department of Electrical and Systems Engineering, University of Pennsylvania, Philadelphia, PA, USA.
5. Kavli Institute at Cornell for Nanoscale Science, Cornell University, Ithaca, NY 14853, USA.