Superconducting properties of novel BiSe${}_2$-based layered LaO${}_{1-x}$F${}_x$BiSe${}_2$ single crystals

Abstract

F-doped LaOBiSe${}_2$ superconducting single crystals with typical size of 2$\times$4$\times$0.2 mm${}^3$ are successfully grown by flux method and the superconducting properties are studied. Both the superconducting transition temperature and the shielding volume fraction are effectively improved with fluorine doping. The LaO${}_{0.48}$F${}_{0.52}$BiSe${}_{1.93}$ sample exhibits zero-resistivity at 3.7 K, which is higher than that of the LaO${}_{0.5}$F${}_{0.5}$BiSe${}_2$ polycrystalline sample (2.4K). Bulk superconductivity is confirmed by a clear specific-heat jump at the associated temperature. The samples exhibit strong anisotropy and the anisotropy parameter is about 30, as estimated by the upper critical field and effective mass model

5 pages, 5 figures, 2 tables, accepted for publication in Europhysics Letter