Point-contact Andreev reflection spectroscopic study of the superconducting gap structure in LuNi2B2C

We employ the point-contact Andreev reflection spectroscopy technique in LuNi 2 B 2 C (T c ∼16.0 K) single crystals along three different crystallographic orientations as a function of magnetic field and temperature. Our data taken on the [001] and [110] faces show gap values at ∼2K of ∼2.4meV, and ∼2.6meV, respectively, as analyzed by the one-gap Blonder-Tinkham-Klapwijk model. Both the energy gap and the Dynes broadening parameter exhibit similar dependences on magnetic field along the two directions. Data taken as a function of temperature follow the BCS-like temperature dependence yielding 2Δ 0 /k B T c ∼3.4 and ∼3.6, respectively. The measured gap values in [100] direction vary from 1.6 to 2.5meV at low temperatures and disappear at the same bulk T c .