1. Institute of Physics Martin Luther University Halle‐Wittenberg 06120 Halle Germany
2. Interdisciplinary Center of Materials Science Martin Luther University Halle‐Wittenberg 06120 Halle Germany
3. Institute of Theoretical Solid State Physics Karlsruhe Institute of Technology 76131 Karlsruhe Germany
4. Institute of Nanotechnology Karlsruhe Institute of Technology 76021 Karlsruhe Germany