Anomalies in velocity of sound: a model study of Kondo and correlation effects in heavy fermion systems

Anomaly in velocity of sound has been analyzed in Kondo lattice model in addition to Heisenberg-type interaction between localized f-electrons. This model is solved by using mean-field approximation to calculate mean field parameters, Kondo singlet lambda and short-ranged f-electrons correlation Gamma. Investigation of anomalies in velocity of sound is presented by considering phonon interaction to bare f-level electrons, c-electrons and to hybridization between c- and f-electrons and phonon Hamiltonian in harmonic approximation. The real part of phonon self-energy contained in phonon Green's function represents velocity of sound for a heavy fermion systems. Temperature-dependent velocity of sound exhibits change in slopes. These findings are compared to experimentally observed facts.