A multiferroic two-dimensional electron gas

TL;DR

This paper reports the discovery of a multiferroic two-dimensional electron gas where ferroelectricity and magnetism coexist, enabling magnetoelectric coupling and opening new avenues in quantum materials research.

Contribution

It demonstrates, for the first time, the coexistence and coupling of ferroelectricity and magnetism in an oxide-based 2DEG, a combination previously thought unlikely in metals.

Findings

Ferroelectricity and magnetism coexist in a 2DEG.

Non-volatile switching of polarization and Hall effect observed.

Magnetoelectric coupling demonstrated in the system.

Abstract

Multiferroics are compounds in which at least two ferroic orders coexist - typically (anti)ferromagnetism and ferroelectricity. While magnetic order can arise in both insulating and conducting compounds, ferroelectricity is in principle not allowed in metals although a few two-dimensional (semi)metals were reported to behave as ferroelectrics. Yet, the combination with magnetic order to realize multiferroic metals remains elusive. Here, by combining x-ray spectroscopy and magnetotransport, we show the coexistence of ferroelectricity and magnetism in an oxide-based two-dimensional electron gas (2DEG). The data evidence a non-volatile switching of the polar displacements and of the anomalous Hall effect by the polarization direction, demonstrating a magnetoelectric coupling. Our findings provide new opportunities in quantum matter stemming from the interplay between ferroelectricity, ferromagnetism and Rashba spin-orbit coupling in a 2DEG.