1. Technische Physik, Wilhelm‐Conrad‐Röntgen‐Research Center for Complex Material Systems, and Würzburg‐Dresden Cluster of Excellence ct.qmat Universität Würzburg Am Hubland D‐97074 Würzburg Germany
2. Institute of Condensed Matter Theory and OpticsFriedrich‐Schiller‐Universität Jena Max‐Wien‐Platz 1 D‐07743 Jena Germany
3. Institute of Physics University of Oldenburg D‐26129 Oldenburg Germany
4. SUPA, School of Physics and Astronomy University of St Andrews St Andrews KY16 9SS UK