In-gap excitation effect on a superexchange in La2CuO4 by creating nonequilibrium photoexcited centers

TL;DR

This paper presents a multielectron theoretical approach to analyze how optical pumping influences superexchange interactions in La2CuO4, revealing an increase in antiferromagnetic exchange energy at resonance conditions.

Contribution

It introduces a novel multielectron calculation method incorporating excited states to study optical effects on superexchange in La2CuO4.

Findings

Antiferromagnetic exchange energy increases with optical excitation.

Resonance light occupation enhances superexchange by approximately 4×10^{-3} eV per %.

Method effectively models nonequilibrium photoexcited states in magnetic insulators.

Abstract

We propose a multielectron approach to calculate superexchange interaction in magnetic Mott- Hubbard insulator La2CuO4(further La214) that allows to obtain the effect of optical pumping on the superexchange interaction. We use the cell perturbation theory with exact diagonalization of the multiband pd Hamiltonian inside each CuO6 unit cell and treating the intercell hopping as perturbation. To incorporate effect of optical pumping we include in this work the excited singlehole local states as well as all two-hole singlets and triplets. By projecting out the interband intercell electron hopping we have obtained the effective Heisenberg-like Hamiltonian with the local spin at site Ri being a superposition of the ground and excited single-hole states. We found that antiferromagnetic contribution to the exchange energy in La214 will increase in accordance to ~ 4*10_{-3} eV /(%) at the resonance light occupation of the excited single hole in-gap state.