Highly-confined spin-polarized two-dimensional electron gas in SrTiO$_{3}$/SrRuO$_{3}$ superlattices

TL;DR

This study uses first principles calculations to reveal a highly confined, spin-polarized two-dimensional electron gas at the interface of SrTiO₃/SrRuO₃ superlattices, with half-metallic ferromagnetic properties and strong electron correlations.

Contribution

It demonstrates the existence of a spin-polarized 2D electron gas confined to Ru 4d orbitals in SrTiO₃/SrRuO₃ superlattices, with a simplified model explaining the electronic and magnetic behavior.

Findings

The superlattice exhibits a spin-polarized 2D electron gas confined to Ru 4d orbitals.

Each interface acts as a minority-spin half-metal ferromagnet with 2.0 μ_B magnetic moment.

Electronic structure and magnetism are explained by a tight-binding model considering t₂g orbitals, bi-dimensionality, and electron correlations.

Abstract

We report first principles characterization of the structural and electronic properties of (SrTiO$_{3}$)$_{5}$/(SrRuO$_{3}$)$_{1}$ superlattices. We show that the system exhibits a spin-polarized two-dimensional electron gas, extremely confined to the 4$d$ orbitals of Ru in the SrRuO$_{3}$ layer. Every interface in the superlattice behaves as a minority-spin half-metal ferromagnet, with a magnetic moment of $\mu$ = 2.0 $\mu_{\rm B}$/SrRuO$_{3}$ unit. The shape of the electronic density of states, half metallicity and magnetism are explained in terms of a simplified tight-binding model, considering only the $t_{2g}$ orbitals plus (i) the bi-dimensionality of the system, and (ii) strong electron correlations.