Modeling multiorbital effects in Sr2IrO4 under strain and a Zeeman field

TL;DR

This study models the complex multiorbital physics of Sr2IrO4 under strain and magnetic fields, revealing phase transitions and the importance of full orbital descriptions for understanding experimental observations.

Contribution

It introduces a comprehensive three-orbital model including interactions, strain, and magnetic field effects, highlighting regimes where full multiorbital descriptions are necessary.

Findings

Identified a continuous metal-insulator transition under strain.

Discovered a first-order magnetic melting of antiferromagnetic order.

Showed bands of J=1/2 and J=3/2 are crucial in phase transitions.

Abstract

We present a comprehensive study of a three-orbital lattice model suitable for the layered iridate Sr2IrO4. Our analysis includes various on-site interactions (including Hubbard and Hund's) as well as compressive strain, and a Zeeman magnetic field. We use a self-consistent mean field approach with multiple order parameters to characterize the resulting phases. While in some parameter regimes the compound is well described by an effective J=1/2 model, in other regimes the full multiorbital description is needed. As a function of the compressive strain, we uncover two quantum phase transitions: first a continuous metal-insulator transition, and subsequently a first order magnetic melting of the antiferromagnetic order. Crucially, bands of both J=1/2 and J=3/2 nature play important roles in these transitions. Our results qualitatively agree with experiments of Sr2IrO4 under strain induced by a substrate, and motivate the study of higher strains.