Direct observation of the influence of the As-Fe-As angle on the Tc of superconducting SmFeAsO$_{1-x}$F$_{x}$

TL;DR

This study demonstrates that the superconducting transition temperature (Tc) in SmFeAsO$_{1-x}$F$_{x}$ is maximized when the FeAs$_{4}$ tetrahedron is regular, highlighting the importance of atomic geometry in superconductivity.

Contribution

It provides direct experimental evidence linking the As-Fe-As angle and tetrahedral regularity to Tc in iron-based superconductors.

Findings

Regular FeAs$_{4}$ tetrahedron correlates with higher Tc.

Pressure-induced changes in structure affect electronic band structures.

Optimization of carrier transfer enhances superconductivity.

Abstract

The electrical resistivity, crystalline structure and electronic properties calculated from the experimentally measured atomic positions of the compound SmFeAsO$_{0.81}$F$_{0.19}$ have been studied up to pressures ~20GPa. The correlation between the pressure dependence of the superconducting transition temperature (Tc) and crystallographic parameters on the same sample shows clearly that a regular FeAs$_{4}$ tetrahedron maximizes Tc, through optimization of carrier transfer to the FeAs planes as indicated by the evolution of the electronic band structures.