Tuning the two-dimensional electron gas at the LaAlO3/SrTiO3(001) interface by metallic contacts

TL;DR

First principles calculations show that metallic overlayers on LaAlO3/SrTiO3(001) can suppress the insulator-to-metal transition, induce metallicity at the surface and interface, and generate spin-polarized 2D electron gases with magnetic moments.

Contribution

This study demonstrates how metallic contacts modify the electronic and magnetic properties of LaAlO3/SrTiO3(001) interfaces, revealing new ways to control 2D electron gases.

Findings

Metallic overlayers eliminate the electric field in LaAlO3 and suppress the insulator-to-metal transition.

Both surface and interface become metallic after metallization, with increased carrier density.

A monolayer Ti contact exhibits magnetic moments and induces spin-polarized 2D electron gases.

Abstract

First principles calculations reveal that adding a metallic overlayer on LaAlO3/SrTiO3(001) eliminates the electric field within the polar LaAlO3 film and thus suppresses the thickness-dependent insulator-to-metal transition observed in uncovered films. Independent of the LaAlO3 thickness both the surface and the interface are metallic, with an enhanced interface carrier density relative to LaAlO3/SrTiO3(001) after the metallization transition. Moreover, a monolayer thick metallic Ti-contact exhibits a finite magnetic moment and for a thin SrTiO3-substrate induces a spin-polarized 2D electron gas at the n-type interface due to confinement effects. A diagram of band alignment in M/LaAlO3/SrTiO3(001) and Schottky barriers for M=Ti, Al, and Pt are provided.