1. Chair in Hybrid Nanosystems, Nano-Institute Munich, Faculty of Physics , Ludwig-Maximilians-Universität München , 80539 Munich , Germany
2. Departamento de Física , Universidade Federal de Pernambuco , 50670-901 Recife-PE , Brazil
3. Center for Nanoscience, Faculty of Physics , Ludwig-Maximilians-Universität München , 80539 Munich , Germany
4. School of Physics and Astronomy , Monash University , Clayton , Victoria 3800 , Australia
5. Department of Physics , Imperial College London , London SW72AZ , UK