ELECTRON-PHONON INTERACTION IN HEAVY-FERMION SYSTEMS

A systematic theory of the electron-phonon interaction in heavy-fermion systems is developed on the basis of the mean-field approximation for the Kondo lattice. The electron-phonon interaction is introduced into the Anderson Hamiltonian by assuming that the hybridization between f electrons and conduction electrons depends on the local lattice strain. The interaction with conduction electrons is included by using a deformation-potential-type coupling. By solving the mean-field equations in the presence of lattice displacements, quasiparticle interactions described by Kondo bosons are included in the present theory. Using a random-phase-type approximation for the Kondo-boson propagators, the phonon self-energy and the elastic constants are calculated. The quasiparticle interaction mediated by phonons is derived, and its competition with the quasiparticle interaction by Kondo bosons is studied. The results of the present theory are compared with an effective static electron-phonon interaction. It is found that this is a reasonable approximation for interaction processes with large momentum transfer and small frequencies. © 1990 The American Physical Society.