1. Department of Physics, Stanford University, Stanford, CA 94305, USA.
2. Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory and Stanford University, Menlo Park, CA 94025, USA.
3. Department of Physics and Astronomy, University of Tennessee, Knoxville, TN 37996, USA.
4. Joint Institute for Advanced Materials, University of Tennessee, Knoxville, TN 37996, USA.
5. Department of Physics and Astrophysics, University of North Dakota, Grand Forks, ND 58202, USA.
6. Geballe Laboratory for Advanced Materials, Stanford University, Stanford, CA 94305, USA.