Quantum oscillations and subband properties of the two-dimensional electron gas at the LaAlO3/SrTiO3 interface

A Mccollam,S Wenderich,G Rijnders,J C Maan,G Koster,M K Kruize,H J A Molegraaf,M Huijben,H Hilgenkamp,A Brinkman,D H A Blank,U Zeitler,V K Guduru

doi:10.1063/1.4863786

Abstract

We have performed high field magnetotransport measurements to investigate the interface electron gas in a high mobility SrTiO3/SrCuO2/LaAlO3/SrTiO3 heterostructure. Shubnikov-de Haas oscillations reveal several 2D conduction subbands with carrier effective masses of 0.9me and 2me, quantum mobilities of order 2000 cm2/V s, and band edges only a few millielectronvolts below the Fermi energy. Measurements in tilted magnetic fields confirm the 2D character of the electron gas, and show evidence of inter-subband scattering.

Highlights

It is well-established that a two-dimensional electron gas (2DEG) can exist at the interface between perovskite oxides LaAlO3 (LAO) and SrTiO3 (STO).[1,2] The 2DEG is nominally similar to those in semiconductor heterostructures, but supports additional phases, such as superconductivity and magnetism, which are not observed in conventional 2D electron systems, and which have great fundamental and technological interest.[3,4] The mechanism of formation of this oxide 2DEG, is not established, and there is a general consensus that the charge carriers occupy STO conduction bands modified by the presence of the interface,[2,5] the origin and density of the 2D carriers, and the details of the electronic bandstructure at the interface are not yet fully understood
Maan1 1High Field Magnet Laboratory and Institute for Molecules and Materials, Radboud University Nijmegen, 6525 ED Nijmegen, The Netherlands 2Faculty of Science and Technology and MESA+ Institute for Nanotechnology, University of Twente, 7500 AE Enschede, The Netherlands (Received 14 December 2013; accepted 19 January 2014; published online 4 February 2014). It is well-established that a two-dimensional electron gas (2DEG) can exist at the interface between perovskite oxides LaAlO3 (LAO) and SrTiO3 (STO).[1,2]
The mechanism of formation of this oxide 2DEG, is not established, and there is a general consensus that the charge carriers occupy STO conduction bands modified by the presence of the interface,[2,5] the origin and density of the 2D carriers, and the details of the electronic bandstructure at the interface are not yet fully understood

Summary

Introduction

It is well-established that a two-dimensional electron gas (2DEG) can exist at the interface between perovskite oxides LaAlO3 (LAO) and SrTiO3 (STO).[1,2] The 2DEG is nominally similar to those in semiconductor heterostructures, but supports additional phases, such as superconductivity and magnetism, which are not observed in conventional 2D electron systems, and which have great fundamental and technological interest.[3,4] The mechanism of formation of this oxide 2DEG, is not established, and there is a general consensus that the charge carriers occupy STO conduction bands modified by the presence of the interface,[2,5] the origin and density of the 2D carriers, and the details of the electronic bandstructure at the interface are not yet fully understood.

Results

Conclusion