1. B. I. Verkin Institute of Low-Temperature Physics and Engineering, Ukrainian Academy of Sciences, pr. Nauki 47, Kharkov 61103, Ukraine
2. The Abdus Salam International Centre for Theoretical Physics, 11 Strada Costiera, I-34151 Trieste, Italy
3. B. I. Verkin Institute of Low-Temperature Physics and Engineering, Ukrainian Academy of Sciences, pr. Nauki 47, Kharkov 61103, Ukraine and V. N. Karazin Kharkov National University, pl. Svobody 4, Kharkov 61000, Ukraine