Orbital and spin order in oxide two-dimensional electron gases

TL;DR

This paper develops a variational theory for multi-band 2D electron gases in oxide heterostructures, revealing how electron density and interactions induce orbital and spin order, with implications for related quantum systems.

Contribution

It introduces a novel variational approach to analyze orbital and spin ordering in multi-band oxide 2DEGs, highlighting the sequence of order formation as density decreases.

Findings

Orbital order appears first at lower densities.

Spin order follows orbital order as interactions strengthen.

Results relate to properties of quantum wells and heterostructures.

Abstract

We describe a variational theory of multi-band two-dimensional electron gases that captures the interplay between electrostatic confining potentials, orbital-dependent interlayer electronic hopping and electron-electron interactions, and apply it to the d-band two-dimensional electron gases that form near perovskite oxide surfaces and heterojunctions. These multi-band two-dimensional electron gases are prone to the formation of Coulomb-interaction-driven orbitally-ordered nematic ground-states. We find that as the electron density is lowered and interaction effects strengthen, spontaneous orbital order occurs first, followed by spin order. We compare our results with known properties of single-component two-dimensional electron gas systems and comment on closely related physics in semiconductor quantum wells and van der Waals heterostructures.