Site selectivity on chalcogen atoms in superconducting La(O,F)BiSSe.

Single crystals of La(O,F)BiSSe were grown by using a CsCl flux method. Single crystal X-ray structural analysis reveals that the crystal structure is isostructural to the BiS2- or BiSe2-based compounds crystallizing with space group P4/nmm (lattice parameters a=4.1110(2)Å, c=13.6010(7)Å). However, the S atoms are selectively occupied at the apical site of the Bi-SSe pyramids in the superconducting layer. The single crystals show a superconducting transition at around 4.2K in the magnetic susceptibility and resistivity measurements. The superconducting anisotropic parameter is determined to be 34-35 from its upper critical magnetic field. The anisotropy is in the same range with that of other members of the La(O,F)BiCh2 (Ch=S, Se) family under ambient pressure. [ABSTRACT FROM AUTHOR]