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Momentum-Dependent Charge Transfer Excitations in Sr2CuO2Cl2 - Angle Resolved Electron Energy Loss Spectroscopy

Y. Y. Wang, F. C. Zhang, V. P. Dravid, K. K. Ng, M. V. Klein, S. E. Schnatterly, L. L. Miller

cond-matarXiv:cond-mat/9606064

Abstract

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 [110], and the latter appear at a higher energy position ( 4.5eV) only along [100], but not along [110]. We interpret these results as transitions involving excitons. A small exciton model is examined to explain both the observed features.

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