Phonon mode coupling in superconducting LuNi2B2C

Abstract

Recently, Kawano et al. reported that an interesting phononlike excitation, localized in q and ω, appears below Tc in the superconducting compound YNi2B2C. This interesting observation led us to perform a series of experiments on the previously studied LuNi2 B2 C superconducting compound covering a large range of q and ω. We demonstrate that there is no new excitation and that the lowest lying excitations can be associated with the Δ4 [ξ00] acoustic and optical phonon branches which exhibit pronounced dips at low temperatures for wave vectors close to the Fermi surface nesting vector, ξm , characteristic of these compounds. Above Tc , as the temperature decreases the frequencies of both modes in the vicinity of ξm decrease and there is a shift of intensity from the upper to the lower mode, an effect characteristic of mode coupling. Below Tc , there is a dramatic decrease in the linewidth of the acoustic mode due to the opening of the superconducting gap.

Source-reported materials — not catalogue approval

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