Growth and anisotropy evaluation of NbBiCh$_3$ (Ch = S, Se) misfit-layered superconducting single crystals

Abstract: NbBiCh$_3$ (Ch = S, Se) misfit-layered superconducting single crystals were successfully grown using a CsCl/KCl flux for the first time. The obtained crystals had a well-developed habit parallel to the c-plane with a typical width of 1-2 mm and thickness of 10-40 um. The superconducting transition temperatures with zero resistivity of NbBiS$_3$ single crystals obtained from the nominal composition of Nb0.9Bi1.2S3 was 0.31 K, and that value of the NbBiSe$_3$ single crystals grown from the stoichiometry composition (NbBiSe$_3$) was 2.3 K. Sharp decreases in electric resistivity and magnetic susceptibility at approximately 3 K suggested a possible superconducting transition temperature of NbBiSe$_3$. The normal-state anisotropy values of grown NbBiS$_3$ and NbBiSe$_3$ single crystals were 2.2-2.4 and 1.5-1.6, respectively.