Atomic scale crystal field mapping of polar vortices in oxide superlattices

Sandhya Susarla; Pablo García-Fernández; Colin Ophus; Sujit Das; Pablo Aguado-Puente; Margaret McCarter; Peter Ercius; Lane W Martin; Ramamoorthy Ramesh; Javier Junquera

doi:10.1038/s41467-021-26476-5

Atomic scale crystal field mapping of polar vortices in oxide superlattices

Nat Commun. 2021 Nov 1;12(1):6273. doi: 10.1038/s41467-021-26476-5.

Authors

Sandhya Susarla^{1

2

3}, Pablo García-Fernández⁴, Colin Ophus⁵, Sujit Das⁶, Pablo Aguado-Puente⁷, Margaret McCarter^{6

8}, Peter Ercius⁵, Lane W Martin^{6

8}, Ramamoorthy Ramesh^{9

10

11

12}, Javier Junquera¹³

Affiliations

¹ National Center for Electron Microscopy, Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA. ssusarla@lbl.gov.
² Department of Materials Science and Engineering, University of California, Berkeley, CA, 94720, USA. ssusarla@lbl.gov.
³ Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA. ssusarla@lbl.gov.
⁴ Departamento de Ciencias de la Tierra y Física de la Materia Condensada, Universidad de Cantabria, Cantabria Campus Internacional, Avenida de los Castros s/n, 39005, Santander, Spain.
⁵ National Center for Electron Microscopy, Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA.
⁶ Department of Materials Science and Engineering, University of California, Berkeley, CA, 94720, USA.
⁷ CIC nanoGUNE BRTA, Donostia - San Sebastián, 20018, Spain.
⁸ Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA.
⁹ National Center for Electron Microscopy, Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA. rramesh@berkeley.edu.
¹⁰ Department of Materials Science and Engineering, University of California, Berkeley, CA, 94720, USA. rramesh@berkeley.edu.
¹¹ Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA. rramesh@berkeley.edu.
¹² Department of Physics, University of California, Berkeley, CA, 94720, USA. rramesh@berkeley.edu.
¹³ Departamento de Ciencias de la Tierra y Física de la Materia Condensada, Universidad de Cantabria, Cantabria Campus Internacional, Avenida de los Castros s/n, 39005, Santander, Spain. javier.junquera@unican.es.

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 [(PbTiO₃)₁₆/(SrTiO₃)₁₆] superlattices at the atomic scale. The peaks in Ti [Formula: see text]-edge spectra shift systematically depending on the position of the Ti⁴⁺ 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.