1. School of Engineering and Science, Jacobs University Bremen, 28759 Bremen, Germany
2. CEA Laboratoire d’electronique des technologies de l’information, 38054 Grenoble, France
3. Department of Physics, University of Bielefeld, 33615 Bielefeld, Germany
4. Department of Physics and Earth Sciences, Jacobs University Bremen, 28759 Bremen, Germany
5. Geballe Laboratory for Advanced Materials, Department of Materials Science and Engineering, Stanford University, Stanford, California 94305, United States