Low temperature Kohn anomaly in metastable fcc lanthanum

Inelastic neutron scattering experiments on a single crystal of the metastable fcc phase of lanthanum metal revealed a pronounced temperature dependent anomaly in the transverse [111] branch of the phonon dispersion curves. A first-principles band structure calculation, in which the 4f states were excluded, yields a Fermi surface with a nesting feature along the [111] direction, which results in a peak in the bare susceptibility at the wave vector of the observed phonon anomaly. (author)