1. Department of Quantum Matter Physics (DQMP), University of Geneva, Quai Ernest-Ansermet 24, 1211 Geneva, Switzerland
2. Institute for Technical Physics, Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany
3. Institute for Theoretical Solid State Physics, Karlsruhe Institute of Technology, Wolfgang-Gaede-Str. 1, 76131 Karlsruhe, Germany