1. Physikalisches Institut; Goethe University; 60438 Frankfurt am Main Germany
2. Physics Department; V. Karazin National University; 61077 Kharkiv Ukraine
3. ICST Faculty; Ukrainian State University of Railway Transport; Kharkiv Ukraine
4. Department of Condensed Matter Physics; Universidad Autonoma de Madrid; Madrid Spain
5. Institute for Theoretical Physics; NSC-KIPT; 61108 Kharkiv Ukraine