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Local-field and excitonic effects in the optical response of α-alumina
Authors: A.G. Marinopoulos, M. Grüning
Ref.: Phys. Rev. B 83, 195129 (2011)
Abstract: This paper introduces key ingredients of the dielectric response of α-alumina that go beyond an independent-particle (IP) treatment of the valence-electron excitations. The optical-response functions were calculated from first- principles both at the BetheSalpeter and the random-phase approximation (RPA) levels. Excitonic effects obtained within the BetheSalpeter framework were found essential for reproducing the low-energy part of the experimental spectra (below 15 eV) and the bound exciton in particular. For higher energies, local-field effects introduced through the RPA modified considerably the IP results and provided a satisfactory account of the reflectivity spectra and of the position and shape of the dominant bulk plasmon resonance in the electron energy-loss spectra.
