1. Ioffe Institute, St. Petersburg 194021, Russia
2. Dresden High Magnetic Field Laboratory, HZDR, Dresden 01328, Germany
3. Wihuri Physical Laboratory, Turku University, Turku 20500, Finland
4. State Key Laboratory of Artificial Microstructure and Mesoscopic Physics, School of Physics, Peking University, Beijing 100871, China
5. Chiba University, Chiba 263-8522, Japan