Superconductivity in Bi₃O₂S₂Cl with Bi–Cl Planar Layers

Abstract

A quaternary compound Bi₃O₂S₂Cl, which consists of novel [BiS₂Cl]^2- layers, is reported. It adopts a layered structure of the space group I4/ mmm (No. 139) with lattice parameters: a = 3.927(1) Å, c = 21.720(5) Å. In this compound, bismuth and chlorine atoms form an infinite planar layer, which is unique among the bismuth halides. Superconductivity is observed in both polycrystals and single crystals, and is significantly enhanced in the samples prepared with less sulfur or at higher temperatures. By tuning the content of sulfur, Bi₃O₂S₂Cl can be converted from a semiconductor into a superconductor. The superconducting critical temperature ranges from 2.6 to 3.5 K. Our discovery of the [BiS₂Cl]^2- layer opens another door in searching for the bismuth compounds with novel physical properties.