Superconductivity in Se-doped La₂O₂Bi₂Pb₂S_6-xSe_xwith a Bi₂Pb₂Ch₄-type thick conducting layer

Department of Physics, Tokyo Metropolitan University - 1-1, Minami-osawa, 192-0397 Hachioji, Japan

^(a) mizugu@tmu.ac.jp

Received: 13 February 2020
Accepted: 9 April 2020

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 La₂O₂Bi₂Pb₂S_6-xSe_x via partial substitution of Se in the S sites. Owing to the Se doping, the normal state electrical resistivity of La₂O₂Bi₂Pb₂S_6-xSe_x 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.