1. Center for Nanoscale Science and Technology, Rice Quantum Institute, and Departments of Chemistry and Physics. Mail Stop 100, Rice University, P.O. Box 1892, Houston, TX 77251, USA.
2. Wavefunction Corp. 18401 von Karman, Suite 370, Irvine, CA 92715, USA.
3. Department of Physics and Astronomy and Center for Fundamental Materials Research, Michigan State University, East Lansing, MI 48824-1116, USA.