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Optical second harmonic generation from LaAlO3/SrTiO3 interfaces with different in-plane anisotropies
Andrea Rubano1, Mateusz Scigaj2, Florencio Sánchez2
1Dipartimento di Fisica 'Ettore Pancini', Università di Napoli 'Federico II', Complesso universitario di Monte Sant'Angelo, via Cintia, 80126 Napoli, Italy.
Journal of Physics. Condensed Matter : an Institute of Physics Journal
|November 29, 2019
Summary
Atomically precise oxide interfaces can exhibit unique electronic properties. Researchers used optical second harmonic generation to confirm that the LaAlO3/SrTiO3(110) interface is polar, resolving debates about its conductivity.
Area of Science:
- Materials Science
- Condensed Matter Physics
- Surface Science
Background:
- Atomically precise oxide growth enables the creation of thin films and interfaces with unique properties not found in bulk materials.
- A two-dimensional electronic gas (2DEG) forms at the LaAlO3/SrTiO3(001) interface, separating two insulating perovskites, with the polar catastrophe model often cited as the cause.
- Controversies exist regarding the conductivity of other LaAlO3/SrTiO3 interfaces, like the (110) orientation, which are predicted to be non-polar but exhibit similar electrical behavior.
Purpose of the Study:
- To investigate the interfacial polarity of LaAlO3/SrTiO3 interfaces with different in-plane orientations.
- To address the lack of experimental tools sensitive to interfacial polarity and resolve controversies surrounding the conductivity of non-polar predicted interfaces.
- To compare experimental findings with theoretical predictions to understand the electronic behavior of these oxide interfaces.
Main Methods:
- Utilized Optical Second Harmonic Generation (SHG) as a sensitive probe for interfacial polarity.
- Investigated LaAlO3/SrTiO3 interfaces with (001) and (110) in-plane orientations.
- Compared experimental SHG results with recent theoretical findings on interfacial electronic reconstruction.
Main Results:
- Optical Second Harmonic Generation successfully probed the polarity of LaAlO3/SrTiO3 interfaces.
- Experimental results, when compared with theoretical findings, indicate that the LaAlO3/SrTiO3(110) interface is strongly polar.
- This finding challenges the simplistic 'ionic' limit predictions for non-polar interfaces that exhibit conductivity.
Conclusions:
- The LaAlO3/SrTiO3(110) interface exhibits strong polarity, contrary to predictions based on the simple ionic model.
- Optical Second Harmonic Generation is a valuable technique for determining interfacial polarity in oxide systems.
- The study resolves controversies regarding the origin of conductivity at LaAlO3/SrTiO3 interfaces with different orientations.
