Orbital Compass Model as an Itinerant Electron System

TL;DR

This paper investigates the two-dimensional orbital compass model as an itinerant electron system, analyzing how on-site Coulomb interactions influence orbital fluctuations and their anisotropy using RPA methods.

Contribution

It introduces a Hubbard-type tight-binding model for the orbital compass system and analyzes the impact of Coulomb interactions on orbital fluctuation anisotropy.

Findings

Orbital fluctuation anisotropy is qualitatively altered by Coulomb interaction.

Dominant fluctuation shifts from intra-band to inter-band nesting with increasing interaction.

The model bridges the orbital compass model with itinerant electron systems.

Abstract

Two-dimensional orbital compass model is studied as an interacting itinerant electron model. A Hubbard-type tight-binding model, from which the orbital compass model is derived in the strong coupling limit, is identified. This model is analyzed by the random-phase approximation (RPA) and the self-consistent RPA methods from the weak coupling. Anisotropy for the orbital fluctuation in the momentum space is qualitatively changed by the on-site Coulomb interaction. This result is explained by the fact that the dominant fluctuation is changed from the intra-band nesting to the inter-band one by increasing the interaction.