1. Max Planck Institute for Solid State Research Heisenbergstr. 1 Stuttgart 70569 Germany
2. Experimental Physics VI Julius‐Maximilians‐University Würzburg Am Hubland Würzburg 97074 Germany
3. Bavarian Center for Applied Energy Research (ZAE Bayern e.V.) Magdalena‐Schoch‐Straße 3 Würzburg 97074 Germany
4. AG Physics of Nanosystems Faculty of Physics Ludwig Maximilians University Amalienstraße 54 München 80799 Germany
5. 1st Physical Institute Faculty of Physics University of Göttingen Friedrich‐Hund‐Platz 1 Göttingen 37077 Germany