ar X iv : c on d - m at / 9 60 10 94 v 1 2 2 Ja n 19 96 Excitons in insulating cuprates
نویسندگان
چکیده
We study the electronic excitations near the charge-transfer gap in insulating CuO 2 planes, starting from a six-band model which includes p π and d xy orbitals and Cu-O nearest-neighbor repulsion U pd. While the low lying electronic excitations in the doped system are well described by a modified t−J model, the excitonic states of the insulator include hybrid d xy − p π states of A 2g symmetry. We also obtain excitons of symmetries B 1g and E u , and eventually A 1g , which can be explained within a one-band model. The results agree with observed optical absorption and Raman excitations.
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