Formation of heavy quasiparticle state in two-band Hubbard model

TL;DR

This paper investigates the formation of heavy quasiparticle states in a two-band Hubbard model, revealing how inter-band Coulomb interactions and electron density influence heavy fermion behavior, with implications for transition metal oxides like LiV2O4.

Contribution

It demonstrates that inter-band Coulomb repulsion stabilizes integral valence and induces heavy quasiparticle states in the two-band Hubbard model, highlighting conditions relevant for transition metal oxides.

Findings

Strong renormalization in the lower band leads to a peak at the Fermi level.

Inter-band Coulomb repulsion U stabilizes integral valence and enhances band mixing.

Hund's-rule coupling J is almost irrelevant when J<U.

Abstract

A realization of heavy fermion state is investigated on the basis of two-band Hubbard model. By means of the slave-boson mean-field approximation, it is shown that for the intermediate electron density, n_e=1.5, the inter-band Coulomb repulsion U strongly emphasizes initially 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<U. The required conditions are suitable for LiV_2O_4, the first observed heavy fermion compound in transition metal oxide.