1. Department of Applied Physics, University of Barcelona, C/Martí i Franquès 1, 08028 Barcelona, Catalonia, Spain
2. ENPHOCAMAT Group, Institute of Nanoscience and Nanotechnology (IN2UB), University of Barcelona, C/Martí i Franquès 1, 08028 Barcelona, Catalonia, Spain
3. Institute of Electronic Structure and Laser, Foundation for Research and Technology─Hellas, 70013 Heraklion, Greece