Formation of a heavy quasiparticle state in the two-band Hubbard model

A realization of a heavy fermion state is investigated on the basis of a two-band Hubbard model. By means of the slave-boson mean-field approximation, it is shown that for the intermediate electron density, nₑ=1.5, the interband Coulomb repulsion U strongly emphasizes initially the small difference between bands, and easily stabilizes integral valence in the lower band. As a result, a strong renormalization takes place in the lower band and the mixing strength between two bands. It gives rise to a sharp peak at the Fermi level in the quasiparticle density of states, as that obtained in the periodic Anderson model. In contrast to a simple insight that the Hund's-rule coupling J reduces the characteristic energy, it turns out to be almost irrelevant to the renormalization for $J