Abstract
Quantitative studies of ultrasound absorption in the heavy-fermion state of ${\mathrm{UPt}}_{3}$ and ${\mathrm{UBe}}_{13}$ are reported. The magnitude of the absorption due to electrons in the normal state is not enhanced compared to that of ordinary metals, indicating a cancellation of the mass enhancement by a reduction of the electron-phonon coupling parameter. This implies that the mass enhancement is described by a different Landau Fermi-liquid parameter than in $^{3}\mathrm{He}$. The ${T}^{2}$ variation of the normal-state sound velocity at lowest temperatures is consistent with the large electronic specific heat.
Highlights
The formation of the heavy-fermion state out of what appears at high temperatures to be local magnetic moments embedded regularly in a metallic matrix is the subject of intensive current research
The question arises whether other properties of the heavy ferrnions are enhanced. One of these is the attenuation of sound, a particular type of transport property, which is determined by the electron-phonon coupling strength and the effective mass of the quasiparticles
The main result is that the magnitude of the ultrasound attenuation is the same as in ordinary metals, and not enhanced by
Summary
The question arises whether other properties of the heavy ferrnions are enhanced One of these is the attenuation of sound, a particular type of transport property, which is determined by the electron-phonon coupling strength and the effective mass of the quasiparticles. This implies, as discussed by karma, ' a compensation of the mass enhancement by a reduction of the electronphonon coupling strength and places severe constraints on any theories for the heavy-fermion state It is the Landau parameter Fo which characterizes the mass enhancement, and not Fl as in the case of the well-studied Fermi-liquid 'He. The experiments on UPt3 were performed on a single crystal grown in an ultrahigh-vacuum float-zone apparatus from a previously synthesized ingot. MHz this gives ql 3.5 x 10 The experimental quantity to be compared with other metals is the ql && 1 limiting at-
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