Quasiparticle spectrum of the hybrids+g-wave superconductorsYNi2B2CandLuNi2B2C

Abstract

Recent experiments on single crystals of ${\mathrm{YNi}}_{2}{\mathrm{B}}_{2}\mathrm{C}$ have revealed the presence of point nodes in the superconducting energy gap $\ensuremath{\Delta}(\mathbf{k})$ at $\mathrm{k\ifmmode \hat{}\else \^{}\fi{}}=(1,0,0),(0,1,0),(\ensuremath{-}1,0,0),$ and $(0,\ensuremath{-}1,0).$ 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.