Distribution of the superconducting gap in an YNi2B2C film studied by point contact spectroscopy

D. L. Bashlakov; Yu. G. Naidyuk; I. K. Yanson; S. C. Wimbush; B. Holzapfel; G. Fuchs; S. -L. Drechsler

doi:10.1088/0953-2048/18/8/012

paper

Distribution of the superconducting gap in an YNi2B2C film studied by point contact spectroscopy

arXiv:cond-mat/0502608 · doi:10.1088/0953-2048/18/8/012

Abstract

The differential resistances $R_{d} = d V / d I (V)$ of point contacts between a normal metal and a c axis oriented YNi2B2C film ( $T_{c}$ = 15.2K) in the superconducting (SC) state have been investigated. $R_{d} (V)$ contains clear "gap" features connected with processes of Andreev reflection at the boundary between normal metal and superconductor that allow the determination of the SC gap $Δ$ and its temperature and magnetic field dependence. A distribution of $Δ$ from $Δ_{m} in \approx$ 1.5 meV to $Δ_{m} a x \approx$ 2.4 meV is revealed; however the critical temperature $T_{c}$ in all cases corresponded to that of the film. The value 2 $Δ_{m} a x / k_{B} T_{c} \approx$ 3.66 is close to the BCS value of 3.52, and the temperature dependence $Δ (T)$ is BCS-like, irrespective of the actual $Δ$ value. It is supposed that the distribution of $Δ$ can be attributed to a gap anisotropy or to a multiband nature of the SC state in YNi2B2C, rather than to the presence of nodes in the gap.

6 two-column pages, 7 figs; V2: as published, Fig.4 is modified