Optical excitations with even symmetry in insulatingcuprates

Abstract

An excitonic cluster model, which can take into account both the strongcorrelation effect of 3d electrons and the itinerant nature of electronicexcitations, and consequently both the bound and unbound states of electronsand holes on the same footing, is applied to describe optical excitations witheven symmetry in insulating cuprates, i.e. parent crystals ofhigh-temperature superconductors. These states are observable in large-shiftRaman scattering and two-photon absorption spectra.