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

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.

• Authors: M P Warusawithana, C Richter, J A Mundy, P Roy, J Ludwig, S Paetel, T Heeg, A A Pawlicki, L F Kourkoutis, M Zheng, M Lee, B Mulcahy, W Zander, Y Zhu, J Schubert, J N Eckstein, D A Muller, C Stephen Hellberg, J Mannhart, D G Schlom
• Journal: Nature communications (Nat Commun) Vol. 4 Pg. 2351 ( 2013) ISSN: 2041-1723 [Electronic] England
• PMID: 23965846 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, Non-P.H.S.)