1. B. Verkin Institute for Low-Temperature Physics and Engineering of the National Academy of Sciences of Ukraine, 47 Nauky Avenue, 61103 Kharkiv, Ukraine
2. Department of Physics, Umeå University, 901 87 Umeå, Sweden
3. Donostia International Physics Center (DIPC), Paseo Manuel de Lardizabal 4, 20018 Donostia-San Sebastian, Spain