Controlled confinement of half-metallic two-dimensional electron gas in BaTiO3/Ba2FeReO6/BaTiO3 heterostructures: A first-principles study

TL;DR

This study uses first-principles calculations to demonstrate that half-metallicity and strong 2D electron confinement are preserved in BaTiO3/Ba2FeReO6/BaTiO3 heterostructures, with potential applications in ultrathin spintronics.

Contribution

It reveals a novel confinement mechanism in heterostructures that enhances 2D electron gas stability and uncovers topological properties in the system.

Findings

Half-metallicity persists down to 1 nm thickness.

Confinement mechanism exceeds that of LaAlO3/SrTiO3 interface.

Nontrivial topological character in (111) heterostructure bands.

Abstract

Using density functional theory calculations, we establish that the half-metallicity of bulk Ba2FeReO6 survives down to 1 nm thickness in BaTiO3/Ba2FeReO6/BaTiO3 heterostructures grown along the (001) and (111) directions. The confinement of the two-dimensional (2D) electron gas in this quantum well structure arises from the suppressed hybridization between Re/Fe d states and unoccupied Ti d states, and it is further strengthened by polar fields for the (111) direction. This mechanism, distinct from the polar catastrophe, leads to an order of magnitude stronger confinement of the 2D electron gas than that at the LaAlO3/SrTiO3 interface. We further show low-energy bands of (111) heterostructure display nontrivial topological character. Our work opens up the possibility of realizing ultrathin spintronic devices.