Topological crystalline insulator phase in graphene multilayers

TL;DR

This paper demonstrates that certain graphene multilayers with specific interlayer twists can host a topological crystalline insulator phase, featuring protected boundary modes and potential for low-dissipation quantum wires.

Contribution

It identifies a new two-dimensional topological insulator phase in graphene multilayers, leveraging crystal symmetry and interlayer twist engineering.

Findings

Graphene multilayers with specific twists are insulators with sizable bandgaps.

These multilayers exhibit a topological phase protected by crystal symmetry.

Boundary modes form low-dissipation quantum wires that can be controlled electrostatically.

Abstract

While the experimental progress on three dimensional topological insulators is rapid, the development of their two dimensional counterparts has been comparatively slow, despite their technological promise. The main reason is materials challenges of the to date only realizations of two-dimensional topological insulators, in semiconductor quantum wells. Here we identify a two dimensional topological insulator in a material which does not face similar challenges and which is by now most widely available and well-charaterized: graphene. For certain commensurate interlayer twists graphene multilayers are insulators with sizable bandgaps. We show that they are moreover in a topological phase protected by crystal symmetry. As its fundamental signature, this topological state supports one-dimensional boundary modes. They form low-dissipation quantum wires that can be defined purely electrostatically.