Hubbard-Kanamori model: spectral functions, negative electron compressibility, and susceptibilities

TL;DR

This study explores the Hubbard-Kanamori model using strong coupling techniques, revealing complex phases, negative electron compressibility regions, and the effects of Hund coupling on magnetic and charge correlations.

Contribution

It provides a detailed phase diagram and insights into electron interactions, spectral functions, and susceptibilities in the two-orbital Hubbard-Kanamori model at various doping levels.

Findings

Four regions of negative electron compressibility at low temperatures.

Presence of Mott and Slater insulators, bad-metal, and spin-polaron states.

Hund coupling enhances antiferromagnetic correlations and suppresses charge and orbital fluctuations.

Abstract

The two-orbital Hubbard-Kanamori model is studied using the strong coupling diagram technique. This approach allows one to take into account the interactions of electrons with spin, charge, and orbital fluctuations of all ranges. It was found that, at low temperatures, the model has four regions of the negative electron compressibility, which can lead to charge inhomogeneities with the assistance of phonons. For half-filling, the phase diagram of the model contains regions of the Mott and Slater insulators, bad-metal, and states with spin-polaron peaks. These sharp peaks at the Fermi level are seen in doped states also. A finite Hund coupling leads to a large increase of antiferromagnetic spin correlations with strong suppression of charge and orbital fluctuations near half-filling. For moderate doping, all types of correlations become comparable. They peak at the antiferromagnetic wave vector except for a narrow region with an incommensurate response. Stronger doping destroys all correlations.