Photoemission Spectrum of Ca2RuO4: Spin Polaron Physics in an S=1 Antiferromagnet with Anisotropies

TL;DR

This paper models the photoemission spectrum of Ca2RuO4 using an S=1 spin polaron framework, revealing how anisotropies influence spectral features and differentiate it from cuprates.

Contribution

It introduces an S=1 spin polaron model for Ca2RuO4 and demonstrates how anisotropies explain spectral peculiarities, advancing understanding of spin polaron physics in this material.

Findings

The model's spectral function matches experimental data qualitatively.

Spin and hopping anisotropies explain spectral differences from cuprates.

Anisotropies, not spin magnitude differences, cause spectral variations.

Abstract

We derive an S=1 spin polaron model which describes the motion of a single hole introduced into the S=1 spin antiferromagnetic ground state of Ca2RuO4. We solve the model using the self-consistent Born approximation and show that its hole spectral function qualitatively agrees with the experimentally observed high-binding energy part of the Ca2RuO4 photoemission spectrum. We explain the observed peculiarities of the photoemission spectrum by linking them to two anisotropies present in the employed model---the spin anisotropy and the hopping anisotropy. We verify that these anisotropies, and not the possible differences between the ruthenate (S=1) and the cuprate (S=1/2) spin polaron models, are responsible for the strong qualitative differences between the photoemission spectrum of Ca2RuO4 and of the undoped cuprates.