Visualizing moir\'e ferroelectricity via plasmons and nano-photocurrent in graphene/twisted-WSe2 structures

TL;DR

This paper demonstrates a novel method to visualize and study moiré ferroelectricity in twisted WSe2 structures by using near-field infrared nano-imaging and nano-photocurrent measurements on graphene heterostructures.

Contribution

It introduces a new approach to visualize ferroelectric domains in moiré heterostructures via plasmonic response in graphene, revealing the local ferroelectric polarization effects.

Findings

Ferroelectric domains are visualized through plasmonic response in graphene.

Graphene's optoelectronic properties are modulated by ferroelectric domains.

The method enables studying moiré ferroelectricity at native length scales.

Abstract

Ferroelectricity, a spontaneous and reversible electric polarization, is found in certain classes of van der Waals (vdW) material heterostructures. The discovery of ferroelectricity in twisted vdW layers provides new opportunities to engineer spatially dependent electric and optical properties associated with the configuration of moir\'e superlattice domains and the network of domain walls. Here, we employ near-field infrared nano-imaging and nano-photocurrent measurements to study ferroelectricity in minimally twisted WSe2. The ferroelectric domains are visualized through the imaging of the plasmonic response in a graphene monolayer adjacent to the moir\'e WSe2 bilayers. Specifically, we find that the ferroelectric polarization in moir\'e domains is imprinted on the plasmonic response of the graphene. Complementary nano-photocurrent measurements demonstrate that the optoelectronic properties of graphene are also modulated by the proximal ferroelectric domains. Our approach represents an alternative strategy for studying moir\'e ferroelectricity at native length scales and opens promising prospects for (opto)electronic devices.