1. Institute for Quantum Materials and Technologies (IQMT), Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany
2. Institute of Nanotechnology, Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany
3. Departamento de Física, Universidad de Oviedo, ES-33007 Oviedo, Spain
4. Centro de Investigación en Nanotecnología y Nanomateriales (CINN, CSIC), El Entrego ES-33940, Spain
5. Kavli Institute of Nanoscience, Delft University of Technology, PO Box 5046, 2600 GA Delft, The Netherlands
6. Institut de Physique et Chimie des Matériaux de Strasbourg (IPCMS), CNRS-Université de Strasbourg, 23, rue du Loess, BP 43, 67034 cedex 2 Strasbourg, France
7. Université de Strasbourg (Unistra), Institute de Science et d′Ingénierie Supramoléculaire (ISIS), Centre Européen de Science Quantique (CESQ), 8, Allée Gaspard Monge, F-67000 Strasbourg, France