Suppression of the Superconducting Transition in RFeAsO1-xFx for R = Tb, Dy, Ho

TL;DR

This paper investigates how the superconducting transition temperature decreases in RFeAsO1-xFx compounds with different rare earth elements, linking it to structural changes and electronic structure crossover.

Contribution

It reveals the relationship between rare earth substitution, structural parameters, and superconductivity suppression in RFeAsO1-xFx materials.

Findings

Critical temperature decreases from 51 K to 36 K across the series.

Superconductivity suppression correlates with Fe-As-Fe angle reduction.

Electronic structure crossover occurs at an optimal geometry.

Abstract

A suppression of superconductivity in the late rare earth RFeAsO1-xFx materials is reported. The maximum critical temperature (Tc) decreases from 51 K for R = Tb to 36 K for HoFeAsO0.9F0.1, which has been synthesised under 10 GPa pressure. This suppression is driven by a decrease in the Fe-As-Fe angle below an optimimum value of 110.6 degrees, as the angle decreases linearly with unit cell volume (V) across the RFeAsO1-xFx series. A crossover in electronic structure around this optimum geometry is evidenced by a change in sign of the compositional dTc/dV, from negative values for previously reported large R materials to positive for HoFeAsO0.9F0.1.