LaAlO3 stoichiometry is key to electron liquid formation at LaAlO3/SrTiO3 
interfaces

Warusawithana, M. P.; Richter, C.; Mundy, J. A.; Roy, P.; Ludwig, J.; Paetel, S.; Heeg, T.; Pawlicki, A. A.; Kourkoutis, L. F.; Zheng, M.; Lee, M.; Mulcahy, B.; Zander, W.; Zhu, Y.; Schubert, J.; Eckstein, J. N.; Muller, D. A.; Hellberg, C. S.; Mannhart, J.; Schlom, D. G.

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LaAlO₃ stoichiometry is key to electron liquid formation at LaAlO₃/SrTiO₃ interfaces

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Mannhart, J.
Department Solid State Quantum Electronics (Jochen Mannhart), Max Planck Institute for Solid State Research, Max Planck Society;

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Citation

Warusawithana, M. P., Richter, C., Mundy, J. A., Roy, P., Ludwig, J., Paetel, S., et al. (2013). LaAlO₃ stoichiometry is key to electron liquid formation at LaAlO₃/SrTiO₃ interfaces. Nature Communications, 4: 2351.

Cite as: https://hdl.handle.net/21.11116/0000-000E-C72B-2

Abstract

Emergent phenomena, including superconductivity and magnetism, found in the two-dimensional electron liquid (2-DEL) at the interface between the insulators lanthanum aluminate (LaAlO3) and strontium titanate (SrTiO3) distinguish this rich system from conventional 2D electron gases at compound semiconductor interfaces. The origin of this 2-DEL, however, is highly debated, with focus on the role of defects in the SrTiO3, while the LaAlO3 has been assumed perfect. Here we demonstrate, through experiments and first-principle calculations, that the cation stoichiometry of the nominal LaAlO3 layer is key to 2-DEL formation: only Al-rich LaAlO3 results in a 2-DEL. Although extrinsic defects, including oxygen deficiency, are known to render LaAlO3/SrTiO3 samples conducting, our results show that in the absence of such extrinsic defects an interface 2-DEL can form. Its origin is consistent with an intrinsic electronic reconstruction occurring to counteract a polarization catastrophe. This work provides insight for identifying other interfaces where emergent behaviours await discovery.