Absence of Hole Confinement in Transition Metal Oxides with Orbital Degeneracy

TL;DR

This paper explores hole movement in a 2D Hubbard model with t_2g electrons, revealing a unique quasi-1D coherent motion driven by three-site terms, and shows orbital degeneracy alone doesn't cause hole self-localization.

Contribution

It demonstrates a novel mechanism for hole motion in orbital models that differs from traditional quantum fluctuation-based explanations.

Findings

Quasi-1D coherent hole motion arises despite Ising-like superexchange.

Orbital degeneracy alone does not induce hole self-localization.

Effective three-site terms enable unique hole propagation mechanisms.

Abstract

We investigate the spectral properties of a hole moving in a two-dimensional Hubbard model for strongly correlated t_2g electrons. Although superexchange interactions are Ising-like, a quasi-one-dimensional coherent hole motion arises due to effective three-site terms. This mechanism is fundamentally different from the hole motion via quantum fluctuations in the conventional spin model with SU(2) symmetry. The orbital model describes also propagation of a hole in some e_g compounds, and we argue that orbital degeneracy alone does not lead to hole self-localization.