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O: Fachverband Oberflächenphysik
O 12: Poster Session I: Electronic structure theory: General
O 12.6: Poster
Monday, March 1, 2021, 10:30–12:30, P
Optical and X-ray absorption spectra of oxides: Theoretical description including many-body effects — •Vijaya Begum1, Markus E. Gruner1, Christian Vorwerk2, Claudia Draxl2, and Rossitza Pentcheva1 — 1Faculty of Physics and Centre for Nanointegration, University of Duisburg-Essen, Duisburg. — 2Institute für Physik and IRIS Adlershof, Humboldt-Universität zu Berlin, Germany.
We present a comprehensive study of the optical and x-ray absorption spectra (XAS)
in two paradigmatic oxides − SrTiO3 (STO) and MgO, from first-principles calculations.
Many-body effects were taken into account by a single step G0W0, followed by the
excitonic effects by solving the Bethe-Salpeter Equation (BSE). The results demonstrate that
the inclusion of the excitonic/electron-(core)hole (e-h) interactions is integral to describe the
spectra accurately. For the optical spectra, the influence of different starting
exchange-correlation functionals [1,2] is discussed, and the best correspondence with
experiment is achieved using a hybrid functional for MgO [2]. The simulated XAS
spectra for the O and Mg K-edge (MgO), and O K-edge (STO) are in excellent agreement with
experiment w.r.t. the spectral shape and peak positions. We also analyze the origin of prominent
peaks in the spectra and identify the orbital character of the relevant contributions by
projecting the e-h coupling coefficients from the BSE eigenvectors on the band structure.
The real-space projection of the respective wave functions in MgO shows a Wannier-Mott type
lowest energy exciton for the optical spectrum, and a strong localization for the O K-edge.
[1] Phys. Rev. Materials 3, 065004 (2019), [2] arXiv:2012.08960v1