2Departamento de Física Teórica de la Materia Condensada and Condensed Matter Physics Center (IFIMAC), Universidad Autónoma de Madrid, E-28049 Madrid, Spain
3Laboratory for Solid State Physics, ETH Zürich, 8093 Zürich, Switzerland
4Quantum Center, ETH Zürich, 8093 Zürich, Switzerland
5Center for Nanophotonics, AMOLF, 1098XG Amsterdam, The Netherlands