The mean field approximation for a system of triplet bosons in nickelates

TL;DR

This paper develops a mean field theory for nickelates modeled as a system of effective spin-triplet bosons, exploring phase competition and separation among charge order, antiferromagnetism, and superconductivity.

Contribution

It introduces a novel mean field approach for triplet boson systems in nickelates, accounting for phase competition and separation in a two-sublattice model.

Findings

Phase diagrams showing coexistence of charge order, antiferromagnetism, and superconductivity.

Identification of phase separation regions.

Insights into the interplay of different phases in nickelates.

Abstract

Rare-earth orthonickelates RNiO3 are Jahn-Teller magnets, unstable with respect to the anti-Jahn-Teller disproportionation reaction with the formation of a system equivalent to a system of effective spin-triplet composite bosons moving in a non-magnetic lattice. Within the framework of the two-sublattice approximation, we have developed a mean field theory for a model nickelate with competition between phases of charge ordering, an antiferromagnetic insulator and a spin-triplet superconductor, and constructed phase diagrams taking into account phase separation.