RIXS studies of magnons and bimagnons in the lightly doped cuprate La2-xSrxCuO4

TL;DR

This study uses RIXS and theoretical calculations to explore how magnetic excitations, including magnons and bimagnons, evolve with doping in lightly doped La2-xSrxCuO4, revealing unchanged magnon dispersion but broadened spectral features.

Contribution

It provides new insights into the doping dependence of magnetic excitations and directly observes bimagnon excitations consistent with previous Raman results.

Findings

Magnon dispersion remains essentially unchanged with doping.

Spectral width broadens as doping increases.

Bimagnon excitations are observed near the zone center with doping-dependent energy scale.

Abstract

We investigated the doping dependence of magnetic excitations in the lightly doped cuprate La2-xSrxCuO4 via combined studies of resonant inelastic x-ray scattering (RIXS) at the Cu L3-edge and theoretical calculations. With increasing doping, the magnon dispersion is found to be essentially unchanged, but the spectral width broadens and the spectral weight varies differently at different momenta. Near the Brillouin zone center, we directly observe bimagnon excitations which possess the same energy scale and doping dependence as previously observed by Raman spectroscopy. They disperse weakly in energy-momentum space, and are consistent with a bimagnon dispersion that is renormalized by the magnon-magnon interaction at the zone center.