Lifting of nodes by disorder in extended-<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>s</mml:mi></mml:math>-state superconductors: Application to ferropnictides

Abstract

We show, using a simple model, how ordinary disorder can gap an extended-$s$- $({A}_{1g})$ symmetry superconducting state with nodes. The concomitant crossover of thermodynamic properties, particularly the $T$ dependence of the superfluid density, from pure power-law behavior to an activated one is exhibited. We discuss applications of this scenario to experiments on the ferropnictide superconductors.