Composition dependence of bulk superconductivity in YFe2Ge2

TL;DR

This study explores how composition and annealing influence the bulk superconductivity in YFe2Ge2, highlighting the importance of minimizing disorder, especially Fe deficiency, to achieve high-quality superconducting samples.

Contribution

It demonstrates that reducing disorder, particularly Fe deficiency, through specific growth and annealing processes enhances bulk superconductivity in YFe2Ge2.

Findings

Superconductivity occurs in samples with low disorder scattering rates.

Fe deficiency is the main source of disorder affecting superconductivity.

Annealing from a slightly iron-rich melt reduces disorder and improves superconducting properties.

Abstract

In the layered iron-based superconductor YFe2Ge2, a high Sommerfeld ratio of ~100 mJ/molK^2 and a T^(3/2) temperature dependence of the electrical resistivity at low temperature T indicate strong electronic correlations and point towards an unconventional pairing state. We have investigated the role of composition and annealing conditions in optimizing the growth of high-quality YFe2Ge2. Our findings confirm that bulk superconductivity is observed in samples with disorder scattering rates less than 2 k_B T_c/hbar. Fe deficiency on the Fe site is identified as the dominant source of disorder, which can be minimised by precipitating from a slightly iron-rich melt, following by annealing.