Spinon-orbiton repulsion and attraction mediated by Hund's rule

TL;DR

This paper investigates how Hund's-rule coupling influences orbital excitations, revealing that it can cause spinon-orbiton attraction or repulsion, which affects spectral features in inelastic x-ray scattering.

Contribution

It demonstrates that the spin-orbit separation interpretation remains valid with Hund's rule and identifies how Hund's coupling induces attractive or repulsive interactions.

Findings

Hund's rule causes either attraction or repulsion between spinon and orbiton.

Spectral weight shifts to lower or upper spectrum edges depending on interaction type.

Spin-orbit separation interpretation is robust despite Hund's-rule effects.

Abstract

We study the impact of Hund's-rule coupling on orbital excitations, as e.g. measured in inelastic resonant x-ray scattering. We find that the interpretation in terms of spin-orbit separation, which has been derived for one-dimensional systems without Hund's rule, remains robust in its presence. Depending on whether or not the orbital excitation includes a spin excitation, Hund's rule leads to an attractive or repulsive interaction between spinon and orbiton. Attraction and repulsion leave clear signatures through a transfer of spectral weight to the lower resp. upper edge of the spectrum.