1. Institute of Applied Physics and DFG-Center for Functional Nanostructures (CFN); Karlsruhe Institute of Technology (KIT); 76128 Karlsruhe Germany
2. Institute of Nanotechnology; Karlsruhe Institute of Technology (KIT); 76128 Karlsruhe Germany
3. Max-Born-Institut; 12489 Berlin Germany
4. School of Mathematical Sciences; University of Technology; Sydney (UTS) NSW 2007 Australia
5. Humboldt-Universität zu Berlin; Institut für Physik, AG Theoretische Optik & Photonik; 12489 Berlin Germany