Abstract
We study the electronic spectral properties at zero temperature of the one-dimensional (1D) version of the degenerate two-orbital Kanamori Hubbard model (KHM), one of the well established frameworks to study transition metal compounds, using state-of-the-art numerical techniques based on the Density Matrix Renormalization Group. While the system is Mott insulating for the half-filled case, as expected for an interacting 1D system, we find interesting and rich structures in the single-particle density of states (DOS) for the hole-doped system. In particular, we find the existence of in-gap states which are pulled down to lower energies from the upper Hubbard band (UHB) with increasing the inter-orbital Coulomb interaction $V$. We analyze the composition of the DOS by projecting it onto different local excitations and we observe that for large dopings these in-gap excitations are formed mainly by inter-orbital holon-doublon (HD) states and their energies follow approximately the HD states in the atomic limit. We observe that the Hund interaction $J$ increases the width of the in-gap band, as expected from the two-particle fluctuations in the Hamiltonian. The observation of a finite density of states within the gap between the Hubbard bands for this extended 1D model indicates that these systems present a rich excitation spectra which could help us understand the microscopic physics behind multi-orbital compounds.
Highlights
Understanding the microscopic mechanisms in materials with strong electron-electron correlations due to interactions in local orbitals, stands out as one of the most challenging problems in condensed matter physics
We study the electronic spectral properties at zero temperature of the one-dimensional (1D) version of the degenerate two-orbital Kanamori-Hubbard model, one of the well-established frameworks to study transition metal compounds, using state-of-the-art numerical techniques based on the density matrix renormalization group
The observation of a finite density of states within the gap between the Hubbard bands for this extended 1D model indicates that these systems present a rich excitation spectra which could help us understand the microscopic physics behind multiorbital compounds
Summary
Understanding the microscopic mechanisms in materials with strong electron-electron correlations due to interactions in local orbitals, stands out as one of the most challenging problems in condensed matter physics. The discovery of a family of materials with similar characteristics in low dimensions, such as those with correlated electrons in ladders, gives us the possibility of a more detailed understanding of the underlying physical mechanisms This is because of the availability of more accurate theoretical and numerical tools for one-dimensional models, such as the density matrix renormalization group (DMRG) technique [3,4,5,6,7]. By carefully analyzing the local electronic density of states (DOS) for a large range of parameters and dopings, we find a well-defined in-gap band for large enough values of the interorbital Coulomb interaction (V ). Previous work reported holon-doublon pairs in related models at higher energies [21,22,23,24], and as metastable states out of equilibrium [25,26], the existence of an in-gap band, such as the one we are presenting in this paper, was not reported before for this model
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