1. Department of Physics and Astronomy, University of British Columbia, Vancouver, BC V6T 1Z1, Canada.
2. Quantum Matter Institute, Vancouver, BC V6T 1Z4, Canada.
3. Max Planck Institute for Chemical Physics of Solids, 01187 Dresden, Germany.
4. Department of Materials Science and Engineering, Stanford Institute for Materials and Energy Sciences, Stanford, CA 94305, USA.
5. Department of Physics, North Carolina State University, Raleigh, NC 27695, USA.