Quantum Nature of Two-Dimensional Electron Gas Confinement at LaAlO₃=SrTiO₃ Interfaces

Authors

Karolina Janicka, University of Nebraska - Lincoln
Julian P. Velev, University of Nebraska-LincolnFollow
Evgeny Y. Tsymbal, University of Nebraska-LincolnFollow

Date of this Version

3-13-2009

Comments

Published in PRL 102, 106803 (2009). Copyright © 2009 The American Physical Society. Used by permission.

Abstract

We perform density functional calculations to understand the mechanism controlling the confinement width of the two-dimensional electron gas (2DEG) at LaAlO₃/SrTiO₃ interfaces. We find that the 2DEG confinement can be explained by the formation of metal induced gap states (MIGS) in the band gap of SrTiO₃. These states are formed as the result of quantum-mechanical tunneling of the charge created at the interface due to electronic reconstruction. The attenuation length of the MIGS into the insulator is controlled by the lowest-decay-rate evanescent states of SrTiO₃, as determined by its complex band structure. Our calculations predict that the 2DEG is confined in SrTiO₃ within about 1 nm at the interface.