1. Institute for Condensed Matter Physics, TU Braunschweig, Braunschweig D-38106,
Germany
2. Center for Correlated Electron Systems, Institute for Basic Science, Seoul 08826, Republic of Korea
3. The Dоnetsk Institute for Physics and Engineering named after O. O. Galkin of NAS of Ukraine, Kyiv
03028, Ukraine
4. B. Verkin Institute for Low Temperature Physics and Engineering of NAS of Ukraine, Kharkiv 61103,
Ukraine
5. Institutfür Mathematische Physik, TU Braunschweig, Braunschweig
D-38106, Germany
6. Physikalisch-Technische Bundesanstalt, D-38116 Braunschweig,
Germany
7. Laboratory of Emerging Nanometrology LENA, Braunschweig D-38106, Germany