1. Institute of Applied Physics of the Academy of Sciences of Moldova; Academic Str. 5 Chisinau 2028 Republic of Moldova
2. Nordita; KTH Royal Institute of Technology and Stockholm University; Roslagstullsbacken 23 Stockholm 10691 Sweden
3. Moscow Institute of Physics and Technology; Inststitutskii per. 9 Dolgoprudnyi 141700 Moscow region Russia
4. Department of Solid State Physics; Institute of Physics, St.Petersburg State University; 1, Ulyanovskaya str. Petrodvorets 198504 St. Petersburg Russia