Local structural distortions and their role in superconductivity in SmFeAsO$_{1-x}$F$_x$ superconductors

TL;DR

This study uses EXAFS to investigate local structural distortions in SmFeAsO$_{1-x}$F$_x$ superconductors, revealing a correlation between anion height variations and superconductivity, similar to high T$_C$ cuprates.

Contribution

It demonstrates the role of local structural distortions, specifically anion height changes, in the emergence of superconductivity in fluorinated SmFeAsO compounds.

Findings

Anion height variation correlates with superconducting onset.

No such variation in non-superconducting samples.

Fe-As bond distance increases near superconducting temperature.

Abstract

EXAFS studies at the As K edge as a function of temperature have been carried out in SmFeAsO$_{1-x}$F$_x$ ($x$ = 0 and 0.2) compounds to understand the role of local structural distortions superconductivity observed in F doped compound. A significant correlation between thermal variation of local structural parameters like anion height and superconducting onset is found in the fluorinated compound. Such a variation in anion height is absent in non-superconducting compound. Increase in Fe-As bond distance just below superconducting onset temperature indicates a similarity in distortions observed in high T$_C$ cuprates and these Fe based superconductors.