Charge Fluctuations in the NdO$_{1-x}$F$_{x}$BiS$_{2}$ Superconductors

TL;DR

This study investigates the atomic structure and charge fluctuations in NdO$_{1-x}$F$_{x}$BiS$_{2}$ superconductors, revealing how local distortions relate to superconductivity suppression.

Contribution

It provides detailed neutron diffraction analysis showing charge-related atomic distortions in superconducting and non-superconducting compositions.

Findings

Ferrodistortive sulfur displacements break tetragonal symmetry.

Superconducting composition shows different distortion magnitudes.

Charge fluctuations may cause charge localization and suppress superconductivity.

Abstract

The local atomic structure of superconducting NdO$_{1-x}$F$_{x}$BiS$_{2}$ ($x$=0.2 and 0.4) is investigated using neutron diffraction and the pair density function analysis technique. In the non-superconducting $x$=0.2 composition, ferrodistortive displacements of the pyramidal sulfur ions break the tetragonal symmetry and a superlattice structure emerges with peaks appearing at $h+k$ odd reflections superimposed on the even reflections of the $P4/nmm$ symmetry. In the superconducting $x$=0.4 composition, similar ferrodistortive displacements are observed but with different magnitudes coupled with in-plane Bi distortions. The distortions are indicative of charge fluctuations that may lead to charge localization and suppression of superconductivity.