1. Institute
of Solid State Physics, Friedrich-Schiller-University Jena, Max-Wien-Platz
1, 07743 Jena, Germany
2. Imperial College London, Prince Consort Road, SW7 2BZ London, United Kingdom
3. Max Planck Institute for the Science of Light, Günther-Scharowsky-Strasse 1, 91058 Erlangen, Germany
4. Helmholtz Center Berlin for Materials and Energy, Hahn-Meitner-Platz 1, 14109 Berlin, Germany