Discovery of a Superconductor Bi 5 O 4 S 3 Cl Containing the Unique BiS 3 Layer.

The BiS 2 -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 5 O 4 S 3 Cl, which crystalizes in a tetragonal structure with P4/mmm (No. 123) space group having alternately stacking unique BiS 3 layers and Bi 2 O 2 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 5 O 4 S 3 Cl becomes metallic when sulfur vacancies are introduced, which hints the origin of superconductivity in Bi 5 O 4 S 3 Cl. The findings will inspire the exploration of new BiS-based superconductors.