title: Giant nonadiabatic effects in layer metals: raman spectra of intercalated graphite explained.
abstract: The occurrence of nonadiabatic effects in the vibrational properties of metals has been predicted since the 1960s, but hardly confirmed experimentally. We report the first fully ab initio calculations of nonadiabatic frequencies of a number of conventional (hcp Ti and Mg) and layered metals (MgB2, CaC6, and other intercalated graphites). Nonadiabatic effects can be spectacularly large (up to 30% of the phonon frequencies) in both cases, but they can only be experimentally observed in the Raman spectra of layered compounds. In layered metals nonadiabatic effects are crucial to explaining the observed Raman shifts and linewidths. Moreover, we show that those quantities can be used to extract the electron momentum-relaxation time.
authors.affiliation: IMPMC, Universités Paris 6 et 7, CNRS, IPGP, 140 rue de Lourmel, 75015 Paris, France.
authors.forename: A Marco
authors.initials: AM
authors.lastname: Saitta
authors.forename: Michele
authors.initials: M
authors.lastname: Lazzeri
authors.forename: Matteo
authors.initials: M
authors.lastname: Calandra
authors.forename: Francesco
authors.initials: F
authors.lastname: Mauri