Quasiparticle spectrum of the hybrid s+g-wave superconductors YNi_2B_2C and LuNi_2B_2C

TL;DR

This paper studies how impurity scattering affects the quasiparticle spectrum in s+g-wave superconductors YNi_2B_2C and LuNi_2B_2C, revealing a gap opening due to disorder and predicting measurable thermodynamic responses.

Contribution

It provides a theoretical analysis of impurity effects on the quasiparticle spectrum in s+g-wave superconductors, highlighting the gap opening even with minimal disorder.

Findings

Impurity scattering opens a gap in the quasiparticle spectrum.

Disorder induces exponentially activated thermodynamic responses.

Predictions can be tested via angular-dependent magnetospecific heat and magnetothermal conductivity measurements.

Abstract

Recent experiments on single crystals of YNi$_2$B$_2$C have revealed the presence of point nodes in the superconducting energy gap Delta(k} at k = (1,0,0), (0,1,0), (-1,0,0), and (0,-1,0). In this paper we investigate the effects of impurity scattering on the quasiparticle spectrum in the vortex state of s+g-wave superconductors, which is found to be strongly modified in the presence of disorder. In particular, a gap in the quasiparticle energy spectrum is found to open even for infinitesimal impurity scattering, giving rise to exponentially activated thermodynamic response functions, such as the specific heat, the spin susceptibility, the superfluid density, and the nuclear spin lattice relaxation. Predictions derived from this study can be verified by measurements of the angular dependent magnetospecific heat and the magnetothermal conductivity.