Evidence of Ferroelectricity in an Antiferromagnetic Vanadium Trichloride Monolayer

TL;DR

This study demonstrates the coexistence of ferroelectricity and antiferromagnetism in a monolayer VCl3, achieved through symmetry breaking via a NbSe2 substrate, with implications for 2D multiferroic device applications.

Contribution

It provides the first direct evidence of ferroelectricity in a 2D antiferromagnetic monolayer VCl3 using experimental and theoretical methods.

Findings

Visualized ferroelectric domains via scanning tunneling spectroscopy

Verified antiferromagnetic order with canted moments

Identified interfacial Cl-Se interactions as key to symmetry breaking

Abstract

A reduced dimensionality of multiferroic materials is highly desired for device miniaturization, but the coexistence of ferroelectricity and magnetism at the two-dimensional limit is yet to be conclusively demonstrated. Here, we used a NbSe2 substrate to break both the C3 rotational and inversion symmetries in monolayer VCl3 and thus introduced exceptional in-plane ferroelectricity into a two-dimensional magnet. Scanning tunneling spectroscopy directly visualized ferroelectric domains and manipulated their domain boundaries in monolayer VCl3, where coexisting antiferromagnetic order with canted magnetic moments was verified by vibrating sample magnetometer measurements. Our density functional theory calculations highlight the crucial role that highly directional interfacial Cl-Se interactions play in breaking the symmetries and thus in introducing in-plane ferroelectricity, which was further verified by examining an ML-VCl3/graphene sample. Our work demonstrates an approach to manipulate the ferroelectric states in monolayered magnets through van der Waals interfacial interactions.