1. Chair for Photonics and Optoelectronics, Nano-Institute Munich, Department of Physics, Ludwig-Maximilians-Universität (LMU), Königinstraße 10, 80539 Munich, Germany
2. Nanosystems Initiative Munich (NIM) and Center for Nanoscience (CeNS), Schellingstraße 4, 80799 Munich, Germany
3. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA), Universidad Nacional de La Plata—CONICET, Sucursal 4 Casilla de Correo 16, 1900 La Plata, Argentina