1. ICFO, Institut de Ciences Fotoniques, The Barcelona Institute of Science and Technology, Castelldefels, Barcelona 08860, Spain
2. The Blackett Laboratory, Department of Physics, Imperial College London, London SW7 2AZ, United Kingdom
3. Departamento de Física, FCEN, IFIBA-CONICET, Universidad de Buenos Aires, C1428EGA, Buenos Aires, Argentina
4. Chair in Hybrid Nanosystems, Nanoinstitute Munich, Ludwig-Maximilians-Universität Munich, 80539, Munich, Germany
5. ICREA, Institució Catalana de Recerca i Estudis Avançats, Barcelona 08010, Spain