SKM 2023 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 33: Perovskite and photovoltaics II (joint session HL/CPP)

CPP 33.6: Vortrag

Mittwoch, 29. März 2023, 11:30–11:45, JAN 0027

Resonant coupling of spin-flip excitations with phonons in BiFeO3 — •Aseem Rajan Kshirsagar and Sven Reichardt — Department of Physics and Material Science, University of Luxembourg, Luxembourg

BiFeO3 is a technologically relevant multiferroic perovskite. While a vast literature exists on its electronic, optical, and multiferroic properties, some of its optically active electronic excitations remain to be understood or have been interpreted in ambiguous ways. This applies in particular to features below the absorption onset that feature prominently in resonant Raman scattering [1]. Here we present a detailed study of the electronic structure and resonant Raman spectrum of BiFeO3 from first principles. Using many-body perturbation theory on top of density functional theory, we first analyze and characterize its optical absorption spectrum in terms of excitons and atomic orbitals, focusing in particular on spin-flip excitations that are strongly localized. We then use the state-of-the-art method for the ab initio calculation of resonant Raman intensities [2,3] to analyze the resonant coupling of these finite-spin excitations with phonons. Our results show that these only weakly optically active excitations still leave a clear imprint on the resonant Raman spectrum, making the latter an even more powerful tool to probe "darker" electronic excitations.

[1] M. C. Weber, et al. Phys. Rev. B, 93, 125204 (2016).

[2] S. Reichardt and L. Wirtz, Phys. Rev. B, 99, 174312 (2019).

[3] S. Reichardt and L. Wirtz, Sci. Adv., 6, eabb5915 (2020).