1. Physik-Department
E20, Technische Universität München, 85748 Garching, Germany
2. Department
of Physics, Chemistry and Biology (IFM), Linköping University, 58183 Linköping, Sweden
3. Institute
of Nanotechnology (INT), Karlsruhe Institute of Technology (KIT), 76344 Eggenstein-Leopoldshafen, Germany
4. IPCMS-CNRS, Université de Strasbourg, 23 rue de Loess, 67034 Strasbourg, France