Ferroelectric valley valves with graphene/MoTe$_2$ van der Waals heterostructures

TL;DR

This paper demonstrates that ferroelectric MoTe$_2$ encapsulated bilayer graphene can act as a switchable topological valley valve, enabling electrically controllable topological channels without external bias, with robustness against moiré effects.

Contribution

It introduces ferroelectric/graphene heterostructures as a new platform for switchable topological channels controlled by ferroelectric order.

Findings

Ferroelectric order controls the topological gap in bilayer graphene.

Topological edge states are robust against moiré modulation.

The heterostructure enables electrically switchable topological channels.

Abstract

Ferroelectric van der Waals heterostructures provide a natural platform to design a variety of electrically controllable devices. In this work, we demonstrate that AB bilayer graphene encapsulated in MoTe$_2$ acts as a valley valve that displays a switchable built-in topological gap, leading to ferroelectrically driven topological channels. Using a combination of ab initio calculations and low energy models, we show that the ferroelectric order of MoTe$_2$ allows the control of the gap opening in bilayer graphene and leads to topological channels between different ferroelectric domains. Moreover, we analyze the effect that the moir\'e modulation between MoTe$_2$ and graphene layers has in the topological modes, demonstrating that the edge states are robust against moir\'e modulations of the ferroelectrically-induced electric potential. Our results put forward ferroelectric/graphene heterostructures as versatile platforms to engineer switchable built-in topological channels without requiring an external electric bias.