A study of the superconducting gap in RNi${}_2$B${}_2$C (R = Y, Lu) single crystals by inelastic light scattering

Abstract

Superconductivity-induced changes in the electronic Raman scattering response were observed for the RNi${}_2$B${}_2$C (R = Y, Lu) system in different scattering geometries. In the superconducting state, 2$\Delta$-like peaks were observed in A${}_{1g}$, B${}_{1g}$, and B${}_{2g}$ spectra from single crystals. The peaks in A${}_{1g}$ and B${}_{2g}$ symmetries are significantly sharper and stronger than the peak in B${}_{1g}$ symmetry. The temperature dependence of the frequencies of the 2$\Delta$-like peaks shows typical BCS-type behavior, but the apparent values of the $2\Delta$ gap are strongly anisotropic for both systems. In addition, for both YNi${}_2$B${}_2$C and LuNi${}_2$B${}_2$C systems, there exists reproducible scattering strength below the $2\Delta$ gap which is roughly linear to the frequency in B${}_{1g}$ and B${}_{2g}$ symmetries. This discovery of scattering below the gap in non-magnetic borocarbide superconductors, which are thought to be conventional BCS-type superconductors, is a challenge for current understanding of superconductivity in this system.

Added text, changed a figure, and added references. Will appear in Phys. Rev. B

References in corpus (1)

• Four-fold basal plane anisotropy of the nonlocal magnetization of YNi2B2C

Cited by in corpus (25)

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• Theoretical study of electronic Raman scattering of Borocarbide superconductors
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