Comparative analysis of specific heat of YNi2B2C using nodal and two-gap models

Abstract

The magnetic field dependence of low temperature specific heat in YNi2B2C was measured and analyzed using various pairing order parameters. At a zero magnetic field, the two-gap model, which has been successfully applied to MgB2 and the point-node model, appear to describe the superconducting gap function of YNi2B2C better than other models based on the isotropic s-wave, the d-wave line nodes, or the s+g wave. The two energy gaps, Delta(L)=2.67 meV and Delta(S)=1.19 meV, are obtained. The observed nonlinear field dependence of the electronic specific heat coefficient, gamma(H)similar to H-0.47, is quantitatively close to the gamma(H)similar to H-0.5 expected for nodal superconductivity or that can be qualitatively explained using a two-gap scenario. Furthermore, the positive curvature in H-c2(T) near T-c is qualitatively similar to that in the other two-gap superconductor MgB2.