Non-collinear and asymmetric polar moments at back-gated SrTiO3 interfaces

• Published in: Communications physics Vol. 5; no. 1; pp. 1 - 8
• Main Authors: Lyzwa, Fryderyk, Pashkevich, Yurii G., Marsik, Premysl, Sirenko, Andrei, Chan, Andrew, Mallett, Benjamin P. P., Yazdi-Rizi, Meghdad, Xu, Bing, Vicente-Arche, Luis M., Vaz, Diogo C., Herranz, Gervasi, Cazayous, Maximilien, Hemme, Pierre, Fürsich, Katrin, Minola, Matteo, Keimer, Bernhard, Bibes, Manuel, Bernhard, Christian
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 30-05-2022; Nature Publishing Group; Nature Portfolio
• Subjects: 639/301/119/995; 639/301/930/527; Asymmetry; Clusters; Electric fields; Electrons; Ellipsometry; Heterostructures; Hysteresis; Lattice vacancies; Oxygen; Physics; Physics and Astronomy; Raman spectroscopy; Spectrum analysis; Strontium titanates
• ISSN: 2399-3650; 2399-3650
• DOI: 10.1038/s42005-022-00905-3

The mechanism of the gate-field-induced metal-to-insulator transition of the electrons at the interface of SrTiO
3
with LaAlO
3
or AlO
x
is of great current interest. Here, we show with infrared ellipsometry and confocal Raman spectroscopy that an important role is played by a polar lattice distortion that is non-collinear, highly asymmetric and hysteretic with respect to the gate field. The anomalous behavior and the large lateral component of the underlying local electric field is explained in terms of the interplay between the oxygen vacancies, that tend to migrate and form extended clusters at the antiferrodistortive domain boundaries, and the interfacial electrons, which get trapped/detrapped at the oxygen vacancy clusters under a positive/negative gate bias. Our findings open new perspectives for the defect engineering of lateral devices with strongly enhanced and hysteretic local electric fields that can be manipulated with various parameters, like strain, temperature, or photons.
The electronic properties of complex oxide heterostructures are governed by the physics at the interface between the different materials. Here, the authors use infrared ellipsometry and confocal Raman spectroscopy to show the presence of non-collinear and asymmetric interfacial polar moments in SrTiO
3
-based heterostructures underlying the important role of oxygen vacancies in these systems.