Emergent inhomogeneity and non-locality in a graphene field-effect transistor on a near-parallel moire superlattice of transition metal dichalcogenides

TL;DR

This study investigates how a twisted bilayer of transition metal dichalcogenides influences the electronic properties of a graphene transistor, revealing emergent inhomogeneity, non-local effects, and valley symmetry breaking driven by interfacial ferroelectricity.

Contribution

It provides detailed electrical transport measurements showing charge inhomogeneity and non-local signals in graphene on twisted WSe2, highlighting the role of moire domains and ferroelectric effects.

Findings

Emergence of multiple local Dirac points with increased electric displacement.

Strong non-local voltage signals at zero displacement field.

Edge mode transport linked to valley symmetry breaking.

Abstract

At near-parallel orientation, twisted bilayer of transition metal dichalcogenides exhibit inter-layer charge transfer-driven out-of-plane ferroelectricity that may lead to unique electronic device architectures. Here we report detailed electrical transport in a dual-gated graphene field-effect transistor placed on 3R stacked twisted bilayer of WSe2 at a twist angle of 2.1 degree. We observe hysteretic transfer characteristics and an emergent charge inhomogeneity with multiple local Dirac points as the electric displacement field (D) is increased. Concomitantly, we also observe a strong non-local voltage signal at D = 0 V/nm that decreases rapidly with increasing D. A linear scaling of the non-local signal with longitudinal resistance suggests edge mode transport, which we attribute to the breaking of valley symmetry of the graphene channel due to the spatially fluctuating electric field from the moire domains of the underlying twisted WSe2. A quantitative analysis connecting the non-locality and channel inhomogeneity suggests emergence of finite-size domains in the graphene channel that modulate the charge and the valley currents simultaneously. This work underlines efficient control and impact of interfacial ferroelectricity that can trigger a new genre of devices for twistronic applications.