Superconductivity in Se-doped La2O2Bi2Pb2S6-xSexwith a Bi2Pb2Ch4-type thick conducting layer

Abstract

La2O2Bi2Pb2S6 is a layered Bi-based oxychalcogenide with a thick four-layer–type conducting layer. Although La2O2Bi2Pb2S6 is a structural analogue of La2O2Bi3AgS6, which is a superconductor, insulating behavior has been observed in La2O2Bi2Pb2S6 at low temperatures, and no superconductivity has been reported. Herein, we demonstrate superconductivity in La2O2Bi2Pb2S6-xSex via partial substitution of Se in the S sites. Owing to the Se doping, the normal state electrical resistivity of La2O2Bi2Pb2S6-xSex at low temperatures was dramatically suppressed, and superconductivity was observed at a transition temperature () of 1.2 K for . increased with increasing Se concentration: for . By applying high pressure for , bulk superconductivity was confirmed and the increased up to 3.6 K at 0.89 GPa.