1. Department of Physics and Astronomy and Quantum Matter Institute, University of British Columbia 1 , Vancouver, British Columbia V6T 1Z1, Canada
2. Department of Mechanical Engineering, University of British Columbia 2 , Vancouver, British Columbia V6T 1Z4, Canada
3. Institute for Theoretical Physics, Georg-August-Universität Göttingen 3 , 37077 Göttingen, Germany