Unconventional correlated metallic behavior due to interorbital Coulomb interaction

Abstract

We study the nondegenerate one-dimensional two-orbital Hubbard model with an interorbital Coulomb inter- action. By means of the density-matrix renormalization group technique, we calculate the local single-particle density of states and the optical conductivity at zero temperature. We find that a finite interorbital Coulomb repulsion V generates a different class of states within the Mott-Hubbard band which has a large weight of holon-doublon pairs, which we hence call the holon-doublon band (HDB). When V is sufficiently large, the HDB specifies the gapless low-energy excitations, and the system becomes an unconventional correlated metal. Optical conductivity results resolve different metallic behaviors for zero and finite interaction V . Compared to the case without an interorbital interaction, the conductivity is strongly reduced in the correlated holon-doublon metal for finite V . In addition, the absorption spectrum is dominated by the HDB, which is clearly distinguishable from the Mott-Hubbard band.