Quantum Hall effect in graphene with twisted bilayer stripe defects

TL;DR

This paper investigates how twisted bilayer stripe defects in graphene influence the quantum Hall effect, revealing that twisting can restore quantized Hall plateaux by decoupling edge states from defect-induced currents.

Contribution

It demonstrates that twisting bilayer stripe defects in graphene reduces Hall conductivity fluctuations, enabling the recovery of quantum Hall plateaux through the formation of quasi-bound states.

Findings

Twisted bilayer stripes decouple edge states from defect currents.

Quantum Hall plateaux are restored at certain twist angles.

Resonant backscattering occurs only at specific energies.

Abstract

We analyze the quantum Hall effect in single layer graphene with bilayer stripe defects. Such defects are often encountered at steps in the substrate of graphene grown on silicon carbide. We show that AB or AA stacked bilayer stripes result in large Hall conductivity fluctuations that destroy the quantum Hall plateaux. The fluctuations are a result of the coupling of edge states at opposite edges through currents traversing the stripe. Upon rotation of the second layer with respect to the continuous monolayer (a twisted-bilayer stripe defect), such currents decouple from the extended edge states and develop into long-lived discrete quasi bound states circulating around the perimeter of the stripe. Backscattering of edge modes then occurs only at precise resonant energies, and hence the quantum Hall plateaux are recovered as twist angle grows.