1. Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada.
2. Quantum Matter Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada.
3. Division of Molecular and Condensed Matter Physics, Department of Physics and Astronomy, Uppsala University, P.O. Box 516, 751 20 Uppsala, Sweden.
4. Max Planck Institute for Solid State Research, 70569 Stuttgart, Germany.
5. Max Planck Institute for Chemical Physics of Solids, 01187 Dresden, Germany.
6. Department of Chemistry, University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada.