1. Institute
of Nanotechnology (INT), Karlsruhe Institute of Technology, 76344 Eggenstein-Leopoldshafen, Germany
2. Institute
of Theoretical Solid State Physics (TFP), Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany
3. Institute
of Physics, University of Münster, 48149 Münster, Germany
4. Department
of Physics, Moscow State Pedagogical University, Moscow 119992, Russia
5. Center
for Functional Nanostructures (CFN), Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany
6. National Research University Higher School of Economics, Moscow 101000, Russia
7. Moscow Institute of Physics and Technology (State University), Moscow 141700, Russia