Excitonic ordering in strongly correlated spin crossover systems: induced magnetism and excitonic excitation spectrum

TL;DR

This paper investigates excitonic ordering in strongly correlated spin crossover systems, revealing induced magnetism, excitonic spectra, and the effects of electron-phonon interactions within an effective Hamiltonian framework.

Contribution

It introduces a detailed analysis of excitonic Bose condensate formation and magnetic ordering in spin crossover systems using the two-band Kanamori model, highlighting new insights into excitonic spectra and phase boundaries.

Findings

Antiferromagnetic order can emerge without interatomic exchange.

Excitonic spectrum exhibits a gap that closes at the condensate boundary.

Spectral weight distribution varies non-uniformly over the Brillouin zone.

Abstract

The effects associated with interatomic hoppings of excitons and the excitonic Bose condensate formation in the strongly correlated spin crossover systems are considered in the framework of the effective Hamiltonian for the two-band Kanamori model. The appearance of antiferromagnetic ordering due to the exciton order is found even in the absence of interatomic exchange interaction. The spectrum of excitonic excitations is calculated at various points of the "temperature vs. crystal field" phase diagram. Outside the region of exciton ordering, the spectrum has a gap, which vanishes at the boundary of the exciton condensate phase. The non-uniform spectral weight distribution over the Brillouin zone is found. The role of electron-phonon interaction is discussed as well.