Atomic scale crystal field mapping of polar vortices in oxide superlattices.

Susarla, Sandhya; García-Fernández, Pablo; Ophus, Colin; Das, Sujit; Aguado-Puente, Pablo; McCarter, Margaret; Ercius, Peter; Martin, Lane W et al. · Nat Commun · 2021

basic_science · Level V

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Abstract

Polar vortices in oxide superlattices exhibit complex polarization topologies. Using a combination of electron energy loss near-edge structure analysis, crystal field multiplet theory, and first-principles calculations, we probe the electronic structure within such polar vortices in [(PbTiO<sub>3</sub>)<sub>16</sub>/(SrTiO<sub>3</sub>)<sub>16</sub>] superlattices at the atomic scale. The peaks in Ti [Formula: see text]-edge spectra shift systematically depending on the position of the Ti<sup>4+</sup> cations within the vortices i.e., the direction and magnitude of the local dipole. First-principles computation of the local projected density of states on the Ti [Formula: see text] orbitals, together with the simulated crystal field multiplet spectra derived from first principles are in good agreement with the experiments.