Calculated positions of point nodes in the gap structure of the borocarbide superconductor YNiBC

Nagai, Yuki*   ; Kato, Yusuke*; Hayashi, Nobuhiko; Yamauchi, Kunihiko*; Harima, Hisatomo*

To determine the superconducting gap function of YNiBC, we calculate the local density of states around a single vortex core with the use of Eilenberger theory and the band structure calculated by local density approximation, assuming various gap structures with point nodes at different positions. We also calculate the angular-dependent heat capacity in the vortex state on the basis of the Doppler-shift method. Comparing our results with the scanning tunneling microscopy and spectroscopy experiment, the angular-dependent heat capacity and thermal conductivity, we propose the gap structure of YNiBC, which has the point nodes and gap minima along . Our gap structure is consistent with all results of angular-resolved experiments.