Field Dependent Superfluid Density in the Optimally Doped SmFeAsO_(1-x)F_y Superconductor

TL;DR

This study investigates how the superfluid density in optimally doped SmFeAsO_(1-x)F_y superconductors decreases with increasing magnetic field, revealing a two-band behavior with different field dependencies.

Contribution

It provides the first combined experimental analysis of field-dependent superfluid density using multiple techniques and models it with a two-band superconductor framework.

Findings

Superfluid density decreases significantly with magnetic field.

The larger gap's superfluid density remains field independent.

The smaller gap's superfluid density is strongly suppressed by the field.

Abstract

The magnetic field dependence of the in-plane magnetic penetration depth for optimally doped SmFeAsO_(1-x)F_y was investigated by combining torque magnetometry, SQUID magnetometry, and muon-spin rotation. The results obtained from these techniques show all a pronounced decrease of the superfluid density as the field is increased up to 1.4 T. This behavior is analysed within a two-band model with self-consistently derived coupled gaps, where the superfluid density related to the larger gap is field independent and the superfluid density related to the smaller gap is strongly suppressed with increasing field.