Resonant inelastic x-ray scattering study of charge excitations in La2CuO4

TL;DR

This study uses resonant inelastic x-ray scattering to investigate charge excitations in La2CuO4, revealing two dispersive exciton modes with distinct energies and momentum-dependent spectral weights, advancing understanding of charge dynamics in cuprates.

Contribution

The paper provides the first detailed measurement of charge transfer excitations' dispersion relations in La2CuO4 using RIXS, identifying two highly dispersive exciton modes.

Findings

Two charge transfer exciton modes with distinct energies and dispersions.

The lower energy mode shows a significant reduction in spectral weight near (π,π).

Both modes are damped by the electron-hole continuum.

Abstract

We report a resonant inelastic x-ray scattering study of the dispersion relations of charge transfer excitations in insulating La$_2$CuO$_4$. These data reveal two peaks, both of which show two-dimensional characteristics. The lowest energy excitation has a gap energy of $\sim 2.2$ eV at the zone center, and a dispersion of $\sim 1$ eV. The spectral weight of this mode becomes dramatically smaller around ($\pi$, $\pi$). The second peak shows a smaller dispersion ($\sim 0.5$ eV) with a zone-center energy of $\sim 3.9$ eV. We argue that these are both highly dispersive exciton modes damped by the presence of the electron-hole continuum.