title: Interplay of low-energy phonons and magnetic excitations in the Kondo insulator YbB12.
abstract: Peculiarities in the lattice dynamics of the Kondo insulator Y bB(12) have been studied by inelastic neutron scattering. Selected phonon modes were traced above and below the temperature region (T ~ 50 K) where the gap opens in the electron density of states. The intensities of some low-energy modes exhibit an anomalous temperature dependence for q vectors close to the Brillouin zone boundary, suggesting a renormalization of the phonon eigenvectors. This effect is thought to arise from a coupling with magnetic excitations of the same symmetry, which exist at nearby energies. It is argued that this magnetovibrational coupling may in turn play a role in the steep temperature crossover existing in Y bB(12) between the low-temperature (Kondo insulator) and high-temperature (incoherent spin-fluctuation) regimes, which is rapidly suppressed by lighter Zr substitution.
authors.affiliation: National Research Centre, Kurchatov Institute, Moscow, Russia. paval@isssph.kiae.ru
authors.forename: P A
authors.initials: PA
authors.lastname: Alekseev
authors.forename: J-M
authors.initials: JM
authors.lastname: Mignot
authors.forename: K S
authors.initials: KS
authors.lastname: Nemkovski
authors.forename: A V
authors.initials: AV
authors.lastname: Rybina
authors.forename: V N
authors.initials: VN
authors.lastname: Lazukov
authors.forename: A S
authors.initials: AS
authors.lastname: Ivanov
authors.forename: F
authors.initials: F
authors.lastname: Iga
authors.forename: T
authors.initials: T
authors.lastname: Takabatake