1. Department of Physics, Technical University of Munich, Garching 85748, Germany
2. Chair in Hybrid Nanosystems, Nanoinstitute Munich, and Center for NanoScience, Faculty of Physics, Ludwig-Maximilians-University Munich, Königinstraße 10, München 80539, Germany
3. School of Physics and Astronomy, Monash University, Clayton, VIC 3800, Australia
4. Department of Physics, Imperial College London, London SW7 2AZ, United Kingdom