Unbalanced edge modes and topological phase transition in gated trilayer graphene

TL;DR

This paper investigates the unique edge modes and topological phase transitions in gated trilayer graphene, revealing unbalanced edge states and valley current polarization, and demonstrating a transition to a ${Z}_2$ topological insulator with spin-orbit coupling.

Contribution

It uncovers unbalanced edge modes and valley current polarization in trilayer graphene, and shows how Rashba spin-orbit coupling induces a topological insulator phase.

Findings

Unbalanced edge modes at opposite zigzag boundaries.

Valley current polarization in trilayer graphene.

Transition to a ${Z}_2$ topological insulator with spin-orbit coupling.

Abstract

Gapless edge modes hosted by chirally-stacked trilayer graphene display unique features when a bulk gap is opened by applying an interlayer potential difference. We show that trilayer graphene with half-integer valley Hall conductivity leads to unbalanced edge modes at opposite zigzag boundaries, resulting in a natural valley current polarizer. This unusual characteristic is preserved in the presence of Rashba spin-orbit coupling that turns a gated trilayer graphene into a ${Z}_2$ topological insulator with an odd number of helical edge mode pairs.