Electron-hole pair excitations in the insulating cuprates Sr2CuO2Cl2 were investigated by angle-resolved electron energy loss spectroscopy. The optically allowed and optically forbidden transitions were observed to be strongly anisotropic in Cu - O2 plane. The former show a large energy dispersion 1.5eV along , and the latter appear at a higher energy position (4.5eV) only along , but not along . We interpret these results as transitions involving excitons. A small exciton model is examined to explain both the observed features.
ASJC Scopus subject areas
- Physics and Astronomy(all)