Pb Substitution Effects on Lattice and Electronic System of the BiS2-based Superconductors La(O F)BiS2

TL;DR

This study investigates how Pb substitution affects the structural, thermal, and electronic properties of LaO0.5F0.5BiS2 superconductors, revealing a first-order phase transition and its correlation with superconductivity suppression.

Contribution

It provides new insights into the interplay between lattice structure and superconductivity in BiS2-based materials with Pb substitution.

Findings

Pb substitution induces a first-order structural phase transition.

Anomalies in thermal and transport properties occur at specific temperatures.

Superconductivity is suppressed near the phase boundary where T* vanishes.

Abstract

We examined the effect of Pb substitution in the layered superconductor LaO0.5F0.5Bi1-xPbxS2 (x=0~0.15) through the measurements of the resistivity, thermal expansion, specific heat, and Seebeck coefficient. These transport and thermal properties show anomalies at certain temperatures (T*) for x${\geq}$0.08. The large thermal expansion anomalies, specific heat anomalies, and the existence of hystereses in the above measurements indicate a first-order structural phase transition at T*. Additionally, the Seebeck coefficient indicates that the anomalies at T* are related not only to the lattice system, but also to the electronic system. Superconductivity is not observed above 2 K at x=0.08, which is around the phase boundary where T* vanishes. The suppression of superconductivity around the structural phase boundary suggests a close relationship between the lattice and superconductivity.