Variation of the extended s-wave superconducting order parameter: From s-wave to g-wave

Abstract

We investigate evolution of properties of an extended [Formula: see text]-wave superconductor, when the order parameter varies from an [Formula: see text]-wave to a [Formula: see text]-wave continuously, by using a model order parameter [Formula: see text]. The evolution of the gap amplitude, the density of states and the specific heat are mainly focused on. For [Formula: see text], due to the existence of a finite sized gap, the characteristic behaviors more or less follow those of the [Formula: see text]-wave. Sudden changes in the characteristic behaviors come out for [Formula: see text], due to appearances of nodes. For [Formula: see text], point nodes in the order parameter on the Fermi surface appear, while for [Formula: see text], line nodes appear. Although they are different kinds of nodes which would usually induce different power-law dependencies in superconducting properties, interestingly enough, they give rise to the same characteristic behavior. The detailed structure of the point nodes for [Formula: see text] is investigated, and it is explained why they lead to the same dependence as the line nodes.