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

Abstract

By means of resonant inelastic x-ray scattering at the Cu L${}_3$ edge, we measured the spin wave dispersion along $⟨$100$⟩$ and $⟨$110$⟩$ 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.

8 pages, 6 figures