Evaluation of insulating behavior by Pb Substitution and Pressure-Induced Superconductivity in La2O2Bi3-xPb1+xS6

TL;DR

This study synthesizes and characterizes La2O2Bi3-xPb1+xS6, revealing pressure-induced superconductivity and a transition from metallic-like to insulating behavior with Pb substitution, advancing understanding of layered bismuth-sulfide compounds.

Contribution

It introduces a new La2O2Bi3PbS6 compound and demonstrates pressure-induced superconductivity in this material, highlighting the effects of Pb substitution and external pressure.

Findings

Pb substitution induces a metal-insulator transition.

Superconductivity appears at 0.93 GPa with a T_c of 3.1 K.

La2O2Bi3PbS6 exhibits narrow gap semiconductor behavior.

Abstract

We report synthesis, characterization, and physical properties of layered bismuth-sulfide compounds La2O2Bi3-xPb1+xS6. We synthesized a new La2O2Bi3PbS6 compound, whose crystal structure is similar to those of the La2O2Bi3AgS6 superconductor or La2O2Bi2Pb2S6 (insulator) with a four-layer-type conducting layer. The crystal structure of La2O2Bi3PbS6 is characterized in a tetragonal P4/nmm space group, and the lattice parameters are a = 4.084(1) {\AA} and c = 19.71(2) {\AA}. The obtained La2O2Bi3PbS6 sample exhibits narrow gap semiconductor (metallic-like) transport behavior with an anomaly near the 160 K. A metallic-like to insulator transition has been observed through Pb substitution, with increasing x in La2O2Bi3-xPb1+xS6. Furthermore, we applied external pressure for x = 0 and observed pressure-induced superconductivity. The onset of superconductivity appeared at 0.93 GPa, and the highest transition temperature was 3.1 K at 2.21 GPa.