ELICO : Electron gas at the Interface between Complex Oxides
Research project selected under the 2016 call for proposals
Principal Investigator :
Walter Escoffier ()
LNCMI (Group « Nano-objects and semi-conducting nano-structures »)
Type of project : Collaborative Project
Partner team(s) :
CEMES
Date (start/end) : 2017 - 2019
Complex oxides display rich physics. The engineering of the electronic properties would yield to multifunctional devices with a strong response to small stimuli activating either the charge, the spin, the lattice or the orbital degrees of freedom. Adapted from P. Zubko et. al., Ann. Rev. Cond. Mat. Phys., Vol. 2: 141-165 (2011)
Abstract
This project aims at investigating the electronic properties of a two-dimensional electron gas at the interface between complex oxides. A decade after its seminal discovery by Ohtomo and Hwang [Nature 427, 423 (2004)] in the canonical system LaAlO 3 /SrTiO 3 , the origin and properties of this intriguing 2D quantum fluid are not yet fully settled, despite the wealth of potential applications. Here, we propose to focus on an alternative system: the interface between (LaAlO 3 ) 0.3 (SrAl 0.5 Ta 0.5 O 3 ) 0.7 (LSAT) and SrTiO 3 (STO) with much higher electronic mobility than its LaAlO 3 /SrTiO 3 counterpart. By combining high field / low temperature magneto-transport and high resolution electron microscopy techniques, we aim at uncover the electronic properties (band-structure and spatial location of the charge carriers) in correlation with the structural properties of the interface. This study will be supported by advanced numerical calculations fully dedicated to the project.
LSAT is a cubic perovskite with a lattice parameter mismatch of only 1% with STO, as compared to 3% between LAO and STO, resulting in a charge carrier mobility improvement. Moreover, LSAT is chemically and thermally stable. Along the [001] direction, the stacking sequence is [La 0.3 Sr 0.7 )O] 0.3+ / [Al 0.65 Ta 0.35 )O 2 ] 0.3- so that a polarization discontinuity arises at the LSAT/STO interface due to the polar nature of LSAT planes. The samples will be provided by Prof. Ariando from the Department of Physics and NUSNNI-Nanocore laboratory at the National University of Singapore. The samples will be grown by Pulsed Laser Deposition with an atomic control of the LSAT/STO interface monitored in situ by RHEED. Samples with various LSAT thicknesses on different STO substrate’s orientation, and with various conditions of growth / post-annealing oxygen partial pressure will be produced and studied. The scientific objectives are two-fold: gain knowledge about the electronic properties of the LSAT/STO interface by mean of low temperature/high magnetic field quantum transport, and correlate these properties with the structural analysis of the interface at the atomic level. Both objectives are complementary and will benefit from a dedicated theoretical support.