Role of valence changes and nanoscale atomic displacements in BiS2-based superconductors

TL;DR

This study investigates how Ce-doping enhances superconductivity in EuBiS2F by analyzing valence changes and atomic displacements, revealing the interplay between charge, structure, and superconducting properties.

Contribution

It provides new insights into the mechanisms of Tc enhancement in BiS2-based superconductors through valence and nanoscale structural analysis.

Findings

Ce-doping increases Tc from 0.3 K to 2.2 K.

Valence changes in Eu are linked to Tc enhancement.

Atomic displacements correlate with superconducting properties.

Abstract

Superconductivity within layered crystal structures has attracted sustained interest among condensed matter community, primarily due to their exotic superconducting properties. EuBiS2F is a newly discovered member in the BiS2-based superconducting family, which shows superconductivity at 0.3 K without extrinsic doping. With 50 at.% Ce substitution for Eu, superconductivity is enhanced with Tc increased up to 2.2 K. However, the mechanisms for the Tc enhancement have not yet been elucidated. In this study, the Ce-doping effect on the self-electron-doped superconductor EuBiS2F was investigated by X-ray absorption spectroscopy (XAS). We have established a relationship between Ce-doping and the Tc enhancement in terms of Eu valence changes and nanoscale atomic displacements. The new finding sheds light on the interplay among superconductivity, charge and local structure in BiS2-based superconductors.