Investigation of the superconducting energy gap in the compound LuNi${}_2$B${}_2$C by the method of point contact spectroscopy: two-gap approximation

Abstract

It is shown that the two-gap approximation is applicable for describing the $dV/dI(V)$ spectra of LuNi${}_2$B${}_2$C-Ag point contacts in a wide interval of temperatures. The values and the temperature dependences of the large and the small gaps in the $ab$ plane and in the $c$ direction were estimated using the generalized BTK model and the equations of Beloborodko. In the BCS extrapolation the critical temperature of the small gap is 10 $K$ in the $ab$ plane and 14.5 $K$ in the $c$ direction. The absolute values of the gaps are ${\Delta }_0^{ab}=2.16$ $meV$ and ${\Delta }_0^c=1.94$ $meV$. For the large gaps the critical temperature coincides with the bulk $T_c$, $T_c^{bulk}=16.8$ $K$, and their absolute values are very close, being about 3 $meV$ in both orientations. In the $c$ direction the contributions to the conductivity from the small and the large gaps remain practically identical up to $10÷11$ $K$. In the $ab$ plane the contribution from the small gap is much smaller and decreases rapidly as a temperature rises.

arXiv comment10 pages, 10 figures, submitted to Fiz. Nizk. Temp. (Low Temp. Phys.)

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• Peculiarities of the superconducting gaps and the electron-boson interaction in TmNi2B2C as seen by point-contact spectroscopy
• Features of Excess Conductivity Behavior in a Magnetic Superconductor Dy${}_{0.6}$Y${}_{0.4}$Rh${}_{3.85}$Ru${}_{0.15}$B${}_4$
• Observation of anisotropic effect of antiferromagnetic ordering on the superconducting gap in ErNi2B2C
• Point-contact study of the LuNi2B2C borocarbide superconducting film
• The Superconducting Gap Behavior in the Antiferromagnetic Nickel-Borocarbide Compounds RNi2B2C (R=Dy, Ho, Er, Tm) Studied by Point-Contacts Spectroscopy
• Nonequilibrium effects in ballistic point contacts Ta-Cu and 2H-NbSe2-Cu. Two-gap superconductivity in 2H-NbSe2