title: NMR relaxation and resistivity from rattling phonons in pyrochlore superconductors.
abstract: We calculate the temperature dependence of the NMR relaxation rate and electrical resistivity for coupling to a local, strongly anharmonic phonon mode. We argue that the two-phonon Raman process is dominating NMR relaxation. Due to the strong anharmonicity of the phonon an unusual temperature dependence is found having a low temperature peak and becoming constant towards higher temperatures. The electrical resistivity is found to vary like T2 at low temperatures and following a square root T behavior at high temperatures. Both results are in qualitative agreement with recent observations on beta-pyrochlore oxide superconductors.
authors.affiliation: Institute for Solid State Physics, University of Tokyo, Kashiwanoha, Kashiwa, Chiba 277-8581, Japan.
authors.forename: Thomas
authors.initials: T
authors.lastname: Dahm
authors.forename: Kazuo
authors.initials: K
authors.lastname: Ueda