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.Comment: 8 pages, 7 figures, published versio
