Correlated motion of particle-hole excitations across the renormalized spin-orbit gap in [formula omitted

Abstract

The high-energy collective modes of particle-hole excitations across the spin-orbit gap in Sr2IrO4 are investigated using the transformed Coulomb interaction terms in the pseudo-spin-orbital basis constituted by the J=1/2 and 3/2 states arising from spin-orbit coupling. With appropriate interaction strengths and renormalized spin-orbit gap, these collective modes yield two well-defined propagating spin-orbit exciton modes, with energy scale and dispersion in excellent agreement with resonant inelastic X-ray scattering (RIXS) measurements.