Dynamical spin susceptibility in La2CuO4 studied by resonant inelastic x-ray scattering

TL;DR

This study demonstrates that resonant inelastic X-ray scattering (RIXS) can quantitatively measure the dynamical spin susceptibility in La2CuO4, aligning well with neutron scattering results, thus establishing RIXS as a powerful tool for studying magnetic excitations in correlated materials.

Contribution

The paper shows that RIXS can be used to quantitatively probe the dynamical spin susceptibility in cuprates, providing a new method complementary to neutron scattering.

Findings

RIXS spectra reveal angular-dependent dd orbital excitations consistent with multiplet calculations.

At low energies, RIXS intensities are proportional to the spin-wave dynamical susceptibility.

RIXS magnon intensities match neutron scattering data when accounting for the spin-flip cross section.

Abstract

Resonant inelastic X-ray scattering (RIXS) is a powerful probe of elementary excitations in solids. It is now widely applied to study magnetic excitations. However, its complex cross-section means that RIXS has been more difficult to interpret than inelastic neutron scattering (INS). Here we report high-resolution RIXS measurements of magnetic excitations of La2CuO4, the antiferromagnetic parent of one system of high-temperature superconductors. At high energies (~2 eV), the RIXS spectra show angular-dependent dd orbital excitations which are found to be in good agreement with single-site multiplet calculations. At lower energies (<0.3 eV), we show that the wavevector-dependent RIXS intensities are proportional to the product of the single-ion spin-flip cross section and the dynamical susceptibility of the spin-wave excitations. When the spin-flip crosssection is dividing out, the RIXS magnon intensities show a remarkable resemblance to INS data. Our results show that RIXS is a quantitative probe the dynamical spin susceptibility in cuprate and therefore should be used for quantitative investigation of other correlated electron materials.