1. LENS, University of Florence, Sesto Fiorentino 50019, Italy
2. Department of Physics and Astronomy, University of Florence, Sesto Fiorentino 50019, Italy
3. Aix Marseille Univ, Université de Toulon, CNRS, IM2NP, Marseille, France
4. Istituto di Fotonica e Nanotecnologie (IFN)-Consiglio Nazionale delle Ricerche, Laboratory for Nanostructure Epitaxy and Spintronics on Silicon, Via Anzani 42, 22100 Como, Italy
5. Department of Physics, Politecnico di Milano, Piazza Leonardo Da Vinci 32, 20133 Milano, Italy