Effective three-band model for double perovskites

TL;DR

This paper develops a simplified three-band model for double perovskites, capturing essential physics of Fe t2g orbitals and enabling analysis of metal-insulator transitions under various conditions.

Contribution

It introduces a low-energy effective Hamiltonian for double perovskites that isolates Fe orbitals and treats electron interactions exactly, improving understanding of their electronic properties.

Findings

Identifies the metal-insulator transition point as a function of pressure.

Provides a framework for analyzing electron correlations in double perovskites.

Demonstrates the effectiveness of the model in capturing key physical phenomena.

Abstract

We start from a six-band model describing the transition-metal t2g orbitals of half-metallic double perovskite systems, such as Sr2FeMoO6, in which only one of the transition metal ions (Fe) contains important intratomic repulsion Ufe. By eliminating the Mo orbitals using a low-energy reduction similar to that used in the cuprates, we construct a Hamiltonian which contains only effective t2g Fe orbitals. This allows to treat exactly Ufe, and most of the Fe-Mo hopping. As an application, we treat the effective Hamiltonian in the slave-boson mean-field approximation and calculate the position of the metal-insulator transition and other quantities as a function of pressure or on-site energy difference.