Exchange and correlation effects in electronic excitations of Cu2O

article provisoireThe state-of-the-art theoretical methods to calculate electronic excitations are shown to fail in describing the highly complex optical absorption spectrum of Cu2O. In particular, the band gap and the optical onset are severely underestimated. We have implemented within a pseudopotential scheme a recently proposed self-consistent quasiparticle approach, based on the GW approximation, and we have extended it to the calculation of optical spectra, including excitonic e®ects. The calculated band structure compares favorably with photoemission data from the literature as well as our present angle-resolved photoemission (ARPES) measurements. Furthermore, the inclusion of the excitonic e®ects using this more precise band structure, together with the better description of the screening, has led to a calculated optical absorption spectrum which reproduces the measured structures. On the basis of these ¯ndings, we give a new interpretation of the origin of the main structures in the spectr