Dynamical mean-field study of the heavy-fermion state in the multi-orbital Anderson lattice model coupled with Jahn-Teller phonons

We investigate the two-orbital Anderson lattice model which includes both the Coulomb interaction between f-electrons and the electron–phonon coupling between f-electrons and Jahn–Teller phonons. The model is solved by using the dynamical mean-field theory in conjunction with the exact diagonalization method. It is found that the heavy fermion state is realized due to the effect of cooperation between the Coulomb interaction and the electron–phonon coupling. Remarkably, the enhancement of lattice fluctuation and the phonon softening observed in the strong coupling regime are largely enhanced due to the Coulomb interaction in contrast to the case with the single-orbital Anderson lattice model