Discovery of a Superconductor Bi₅ O₄ S₃ Cl Containing the Unique BiS₃ Layer

The BiS₂ -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, Bi₅ O₄ S₃ Cl, which crystalizes in a tetragonal structure with P4/mmm (No. 123) space group having alternately stacking unique BiS₃ layers and Bi₂ O₂ 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 Bi₅ O₄ S₃ Cl becomes metallic when sulfur vacancies are introduced, which hints the origin of superconductivity in Bi₅ O₄ S₃ Cl. The findings will inspire the exploration of new BiS-based superconductors.