Topological crystalline insulators from stacked graphene layers

TL;DR

This paper proposes a method to create topological crystalline insulators using stacked graphene layers with polar spacers, enabling new electronic phases through doping and spin-orbit effects.

Contribution

It introduces a novel heterostructure design for TCIs that are protected by mirror symmetry and can be controlled by external perturbations.

Findings

Graphene heterostructures can host topological phases with mirror symmetry protection.

External magnetic fields induce quantum Hall phases with opposite Chern numbers.

Non-trivial topology can be achieved without intrinsic spin-orbit coupling, using doping and external fields.

Abstract

In principle the stacking of different two-dimensional (2D) materials allows the construction of 3D systems with entirely new electronic properties. Here we propose to realize topological crystalline insulators (TCI) protected by mirror symmetry in heterostructures consisting of graphene monolayers separated by two-dimensional polar spacers. The polar spacers are arranged such that they can induce an alternating doping and/or spin-orbit coupling in the adjacent graphene sheets. When spin-orbit coupling dominates, the non-trivial phase arises due to the fact that each graphene sheet enters a quantum spin-Hall phase. Instead, when the graphene layers are electron and hole doped in an alternating fashion, a uniform magnetic field leads to the formation of quantum Hall phases with opposite Chern numbers. It thus has the remarkable property that unlike previously proposed and observed TCIs, the non-trivial topology is generated by an external time-reversal breaking perturbation.