Phase segregation of superconductivity and ferromagnetism at LaAlO$_3$/SrTiO$_3$ interface

TL;DR

This paper investigates how disorder-induced phase separation explains the coexistence of superconductivity and ferromagnetism at the LaAlO3/SrTiO3 interface, revealing inhomogeneous electronic states.

Contribution

It demonstrates that strong disorder causes spatial separation of superconducting and ferromagnetic regions, elucidating their coexistence at the interface.

Findings

Strong disorder leads to phase separation.

Superconductivity and ferromagnetism occupy mutually exclusive regions.

Inhomogeneity explains coexistence phenomena.

Abstract

The highly conductive two-dimensional electron gas formed at the interface between insulating SrTiO$_3$ and LaAlO$_3$ shows low-temperature superconductivity coexisting with inhomogeneous ferromagnetism. The Rashba spin-orbit interaction with in-plane Zeeman field of the system favors $p_x \pm i p_y$-wave superconductivity at finite momentum. Owing to the intrinsic disorder at the interface, the role of spatial inhomogeneity on the superconducting and ferromagnetic states becomes important. We find that for strong disorder, the system breaks up into mutually excluded regions of superconductivity and ferromagnetism. This inhomogeneity-driven electronic phase separation accounts for the unusual coexistence of superconductivity and ferromagnetism observed at the interface.