1. Center for Hybrid Nanostructures (CHyN), Universität Hamburg, Luruper Chaussee 149, Hamburg 22761 Germany
2. Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität zu Kiel, Leibnizstrasse 19, 24098 Kiel, Germany
3. I. Institute for Theoretical Physics, Universität Hamburg, Luruper Chaussee 149, Hamburg 22761 Germany
4. ICMM-CSIC, Sor Juana Inés de la Cruz 3, Madrid 28049 Spain
5. International Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
6. Research Center for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
7. Material Science and Engineering, University of Wisconsin-Madison, University Ave. 1550, Madison 53706, Wisconsin, USA