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

TL;DR

This study reports the discovery of superconductivity in Se-doped La2O2Bi2Pb2S6, a layered oxychalcogenide, where Se substitution induces metallicity and superconductivity at low temperatures, expanding the family of Bi-based superconductors.

Contribution

The paper demonstrates that Se doping induces superconductivity in La2O2Bi2Pb2S6, revealing the role of in-plane chemical pressure in promoting superconductivity in layered Bi-based oxychalcogenides.

Findings

Superconductivity observed at Tc = 1.15 K for x=0.5

Tc increases to 1.9 K with higher Se content

Se doping suppresses resistivity and induces metallicity

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 (Tc) of 1.15 K for x = 0.5. Tc increased with increasing Se concentration: Tc = 1.9 K for x = 1.0. The emergence of metallicity and superconductivity was explained via in-plane chemical pressure effects that can suppress local disorder and carrier localization, which are commonly observed in two-layer-type BiS2-based systems.