Superconducting properties of BiSe ₂ -based LaO _1−x F _x BiSe ₂ single crystals

Abstract

F-doped LaOBiSe$_{2}$ superconducting single crystals with typical size of\n2$\\times$4$\\times$0.2 mm$^{3}$ are successfully grown by flux method and the\nsuperconducting properties are studied. Both the superconducting transition\ntemperature and the shielding volume fraction are effectively improved with\nfluorine doping. The LaO$_{0.48}$F$_{0.52}$BiSe$_{1.93}$ sample exhibits\nzero-resistivity at 3.7 K, which is higher than that of the\nLaO$_{0.5}$F$_{0.5}$BiSe$_{2}$ polycrystalline sample (2.4K). Bulk\nsuperconductivity is confirmed by a clear specific-heat jump at the associated\ntemperature. The samples exhibit strong anisotropy and the anisotropy parameter\nis about 30, as estimated by the upper critical field and effective mass model\n