SKM 2023 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 26: Focus Session: Frontiers of Electronic-Structure Theory IV (joint session O/HL)
HL 26.4: Talk
Wednesday, March 29, 2023, 11:30–11:45, TRE Ma
A combined G0W0/BSE scheme of characterizing photoexcitations in hydroxylated rutile TiO2(110) — •Savio Laricchia, Andrea Ferretti, Daniele Varsano, and Claudia Cardoso — Centro S3, CNR-Istituto Nanoscienze, 41125 Modena, Italy
In reduced TiO2, electronic transitions originating from polaronic excess electrons in surface-localized band-gap sta tes (BGS) are known to contribute to the photoabsorption and to the photocatalytic response of TiO2 in the visible region. Recent state-selective studies using two-photon photoemission (2PPE) spectroscopy have also identified an alternative photoexcitation mechanism contributing to the photoabsorption of the reduced surface (110) of rutile TiO2. This process involves d-d excitations from BGS arising from surface and subsurface defects, including bridging hydroxyls and oxygen vacancies. Density Functional Theory (DFT) has been used to determine the character of the electronic excited states involved in a dt2g-dt2g transitions, but its accuracy is questioned by its theoretical framework: DFT is in principle exact for ground state systems and does not describe interacting photogenerated electron-hole pairs, i.e. the excitons. This has highlighted the need to move beyond the DFT formalism, by working within a many-body perturbation theory (MBPT) framework. It will be shown how a G0W0 method, combined with the solution of the Bethe-Salpeter equation (BSE), provides a powerful tool for characterizing from first principles the optical excitations from BGS identified by 2PPE experiments on hydroxylated TiO2(110).