1. Chair for Photonics and Optoelectronics, Department of Physics, Ludwig-Maximilians-Universität München, Amalienstraße 54, 80799 Munich, Germany
2. Nanosystems Initiative Munich 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
4. Max Planck Institute for Intelligent Systems, Heisenbergstraße 3, 70569 Stuttgart, Germany