Site Selectivity on Chalcogen Atoms in Superconducting La(O,F)BiSSe

TL;DR

This study reports the growth and structural analysis of La(O,F)BiSSe single crystals, revealing selective S atom occupation and superconductivity at 4.2 K, with anisotropic properties similar to related compounds.

Contribution

First successful growth of La(O,F)BiSSe single crystals and detailed structural and superconducting property analysis.

Findings

Superconducting transition at 4.2 K observed.

Selective S atom occupation at apical sites.

Superconducting anisotropic parameter is 34.

Abstract

Single crystals of La(O,F)BiSSe were successfully grown by a CsCl flux method. Single crystal X-ray structural analysis revealed that the crystal structure is isostructural with BiS$_2$- or BiSe$_2$-based compounds with space group $P4/nmm$ (lattice parameters $a$ = 4.1110(2) {\AA}, $c$ = 13.6010(7) {\AA}). 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 4.2 K in the magnetic susceptibility and resistivity measurement. The superconducting anisotropic parameter is determined to be 34 from its upper critical magnetic field. The anisotropy is in the same range with that of other members of the La(O,F)BiCh$_2$ ($Ch$ = S, Se) family under ambient pressure.