Evidence of multiband superconductivity in the quaternary borocarbide superconductor YNi2B2C using directional point-contact spectroscopy

In this paper, we review our recent investigations on the gap anisotropy of the quaternary borocarbide superconductor YNi2B2C using directional point-contact spectroscopy. Through a detailed study of the temperature and magnetic field dependence of the superconducting energy gaps we show that the gap anisotropy in this material originates from electrons on different Fermi sheets having very different Fermi velocities. The gap anisotropy in this material is therefore well explained through a multiband scenario where electrons in different k-directions have very different electron-phonon coupling strength.