Intrinsic instability of electronic interfaces with strong Rashba coupling

TL;DR

This paper models a 2D electron gas at oxide interfaces with Rashba spin-orbit coupling, revealing an intrinsic phase separation instability that may explain observed inhomogeneous phases.

Contribution

It demonstrates that a simple model with Rashba coupling and polarity effects predicts an intrinsic phase separation at oxide interfaces.

Findings

Phase separation instability occurs at realistic parameters.

The instability could explain inhomogeneous phases observed experimentally.

Rashba coupling plays a key role in interface electronic behavior.

Abstract

We consider a model for the two-dimensional electron gas formed at the interface of oxide heterostructures, which includes a Rashba spin-orbit coupling proportional to the electric field perpendicular to the interface. Based on the standard mechanism of polarity catastrophe, we assume that the electric field is proportional to the electron density. Under these simple and general assumptions, we show that a phase separation instability occurs for realistic values of the spin-orbit coupling and of the band parameters. This could provide an intrinsic mechanism for the recently observed inhomogeneous phases at the LaAlO_3/SrTiO_3 or LaTiO_3/SrTiO_3 interfaces.