1. Max Planck Institute for Solid State Research 70569 Stuttgart Germany
2. Department of Physics University of Central Florida Orlando FL 32816 USA
3. Renewable Energy and Chemical Transformations Cluster University of Central Florida Orlando FL 32816 USA
4. Institut de Physique Ecole Polytechnique Fédérale de Lausanne Lausanne CH‐1015 Switzerland
5. Institute of Applied Physics Technische Universität Braunschweig 38106 Braunschweig Germany