The nickel borocarbides RNi2B2C, R = Y or Lu, have a superconducting Tc of 15-16K and exhibit properties consistent with an anisotropic s-wave gap. We briefly review their properties. Electronic Raman scattering results are presented on YNi2B2C containing 11B or 10B. In A1g and B1g Raman symmetries, there is no shift in the position of the '2Δ' peak with B-isotope. There is a distinct negative shift, however, in B2g symmetry. This is interpreted as a negative isotope shift for the gap Δ on that portion of the Fermi surface where the magnitude of the B2g Raman vertex is large.
Bibliographical noteFunding Information:
I-SY was supported by BK21 and KRF-2000-015-DS0014 of Korea and by residual state funds for the Science and Technology Center for Superconductivity at Urbana. The work at Ames Laboratory was funded by the US Department of Energy under Contract No. W-7405-Eng-82.
- A. Superconductors
- D. Phonons