Discovery of a Superconductor Bi O S Cl Containing the Unique BiS Layer.

The BiS -based layered superconductors with structures similar to those of cuprates and iron-based superconductors have stimulated much research interest. Here, a new quaternary compound is reported, Bi O S Cl, which crystalizes in a tetragonal structure with P4/mmm (No. 123) space group having alternately stacking unique BiS layers and Bi O layers along the c-axis with a Cl atom located at the center of the unit cell. A superconducting transition above 3 K is observed for both electrical transport and magnetic measurements. Hall resistivity measurements show its multiband character with a conduction dominated by electron-like charge carriers. The first-principles calculations exhibit that the semiconducting parent phase Bi O S Cl becomes metallic when sulfur vacancies are introduced, which hints the origin of superconductivity in Bi O S Cl. The findings will inspire the exploration of new BiS-based superconductors.