ELECTRON-PHONON INTERACTION AND PHONON RESPONSE IN HEAVY FERMION SYSTEMS

Abstract

The phonon response property of the Heavy Fermion (HF) systems are investigated within the Periodic Anderson Model (PAM) to explain the observed phonon anomalies. To understand the microscopic origin of these anomalies, two different mechanisms of electron-phonon interaction, namely, the usual interaction between the phonons and the electrons in the f-bands as well as the interaction due to the hybridization term of PAM, are considered. The influence of coulomb correlation U on the phonon excitation spectrum and the spectral density function are studied for various model parameters, namely, the position of the f-level E0, the ratio r of the electron-phonon coupling strengths f1(q) and f2(q), and the effective coupling strength g. The numerical evaluations of these phonon response functions are carried out for small temperatures in the long wavelength limit, while retaining terms which are linear in correlation. The observed behavior agrees well with the general features obtained in experiment.