1. Stewart Blusson Quantum Matter Institute, University of British Columbia, Vancouver, BC V6T 1Z4, Canada, and Department of Physics and Astronomy, University of British Columbia, Vancouver, BC V6T 1Z1, Canada.
2. Department of Physics, University of Washington, Seattle, WA 98195, USA.
3. Department of Materials Science and Engineering, University of Washington, Seattle, WA 98195, USA.