Superfluid density and penetration depth in Fe-pnictides

TL;DR

This paper analyzes the superfluid density in Fe-pnictides, showing it behaves similarly to an s-wave superconductor with magnetic impurities, and explains experimental penetration depth data.

Contribution

It demonstrates that superfluid density in Fe-pnictides follows a power-law due to impurity scattering, aligning with some experimental results and extending understanding of their superconducting properties.

Findings

Superfluid density exhibits a power-law temperature dependence with n≈1.6-2.

Behavior is similar to s-wave superconductors with magnetic impurities.

Results align with penetration depth measurements in BaFe₂As₂.

Abstract

We consider the superfluid density $\rho_s (T)$ in a two-band superconductor with extended s-wave symmetry ($s^+$) in the presence of non-magnetic impurities and apply the results to Fe-pnictides. We show that the behavior of the superfluid density is essentially the same as in an ordinary s-wave superconductor with magnetic impurities. We show that, for moderate to strong inter-band impurity scattering, $\rho_s (T)$ behaves as a power-law $T^n$ with $n\approx 1.6\div2$ over a wide range of $T$. We argue that the power-law behavior is consistent with recent experiments on the penetration depth $\lambda (T)$ in BaFe$_2$As$_2$, but disagree quantitatively with the data on LaFePO.