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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
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Abstract

The differential resistances $R_d=dV/dI(V)$ 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 $Δ_min\approx$ 1.5 meV to $Δ_max\approx$ 2.4 meV is revealed; however the critical temperature $T_c$ in all cases corresponded to that of the film. The value 2$Δ_max/k_BT_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.

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D. L. Bashlakov, Yu. G. Naidyuk, I. K. Yanson, S. C. Wimbush, B. Holzapfel, G. Fuchs, S. -L. Drechsler. 2005-07-06. Distribution of the superconducting gap in an YNi2B2C film studied by point contact spectroscopy. https://doi.org/10.1088/0953-2048%2F18%2F8%2F012

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