1Institute for Theoretical Solid State Physics and Würzburg-Dresden Cluster of Excellence ct.qmat, IFW Dresden, Helmholtzstr. 20, 01069 Dresden, Germany
2Max Planck Institute for Solid State Research, Heisenbergstrasse 1, D-70569 Stuttgart, Germany
3Department of Physics and Astronomy, University of British Columbia, Vancouver B.C. V6T 1Z1, Canada
4Stewart Blusson Quantum Matter Institute, University of British Columbia, Vancouver B.C. V6T 1Z4, Canada
