Resonant inelastic X-ray scattering study of spin-wave excitations in the cuprate parent compound Ca$_{2}$CuO$_2$Cl$_2$

TL;DR

This study uses resonant inelastic X-ray scattering to measure spin-wave excitations in the undoped cuprate Ca$_{2}$CuO$_2$Cl$_2$, providing precise estimates of superexchange interactions and insights into magnetic properties relevant for understanding cuprate physics.

Contribution

First direct measurement of spin-wave dispersion in Ca$_{2}$CuO$_2$Cl$_2$ using RIXS, offering accurate superexchange parameters and comparison with theoretical models.

Findings

Superexchange parameter J = 135 ± 4 meV

Next-nearest neighbor interactions are intermediate between La$_{2}$CuO$_4$ and Sr$_2$CuO$_2$Cl$_2$

40 meV dispersion indicates significant magnetic interactions

Abstract

By means of resonant inelastic x-ray scattering at the Cu L$_3$ edge, we measured the spin wave dispersion along $\langle$100$\rangle$ and $\langle$110$\rangle$ in the undoped cuprate Ca$_2$CuO$_2$Cl$_2$. The data yields a reliable estimate of the superexchange parameter $J$ = 135 $\pm$ 4 meV using a classical spin-1/2 2D Heisenberg model with nearest-neighbor interactions and including quantum fluctuations. Including further exchange interactions increases the estimate to $J$ = 141 meV. The 40 meV dispersion between the magnetic Brillouin zone boundary points (1/2,\,0) and (1/4,\,1/4) indicates that next-nearest neighbor interactions in this compound are intermediate between the values found in La$_{2}$CuO$_4$ and Sr$_2$CuO$_2$Cl$_2$. Owing to the low-$Z$ elements composing Ca$_2$CuO$_2$Cl$_2$, the present results may enable a reliable comparison with the predictions of quantum many-body calculations, which would improve our understanding of the role of magnetic excitations and of electronic correlations in cuprates.