Magnetic couplings, optical spectra, and spin-orbit exciton in 5d electron Mott insulator Sr2IrO4

TL;DR

This paper models the magnetic and optical properties of Sr2IrO4, a 5d electron Mott insulator, using a microscopic approach that includes spin-orbit coupling, Coulomb interactions, and crystal field effects, successfully explaining experimental observations.

Contribution

It provides a comprehensive microscopic model that accounts for magnetic couplings and optical spectra, including the spin-orbit exciton, in Sr2IrO4, with detailed calculations matching experiments.

Findings

Calculated magnetic coupling constants match experimental data.

Optical conductivity shows two peaks at ~0.5 and 1.0 eV, consistent with experiments.

Identified the origin of the two-peak structure as Fano-type overlap involving spin-orbit exciton.

Abstract

Based on the microscopic model including strong spin-orbit coupling, on-site Coulomb and Hund's interactions, as well as crystal field effects, we have investigated magnetic and optical properties of Sr2IrO4. Taking into account all possible intermediate state multiplets generated by virtual hoppings of electrons, we calculated the isotropic Heisenberg, pseudodipolar, and Dzyaloshinsky-Moriya coupling constants, which describe the experiment quite well. We have also evaluated the optical conductivity {\sigma}({\omega}) by employing the exact diagonalization method on small clusters, and obtained two peaks at \sim 0.5 and \sim 1.0 eV in agreement with experiment. The two peak structure of {\sigma}({\omega}) arises from the unusual Fano-type overlap between electron-hole continuum of the Jeff = 1/2 band and the intrasite spin-orbit exciton observed recently in Sr2IrO4 by resonant x-ray scattering.