Interplay between topological protected valley and quantum Hall edge transport

TL;DR

This study investigates the complex interaction between topologically protected states at stacking domain walls and quantum Hall edge transport in bilayer graphene, revealing how magnetic field strength influences conductance and spectral properties.

Contribution

It provides new insights into the interplay between topological domain wall states and quantum Hall edge transport in bilayer graphene, highlighting the effects of magnetic field on conductance and spectral gaps.

Findings

Conductance remains stable at low magnetic fields across quantum Hall states.

Transport suppression occurs at high magnetic fields due to spectral minigaps.

Stacking domain walls may not always act as topological domain walls.

Abstract

An established way of realizing topologically protected states in a two-dimensional electron gas is by applying a perpendicular magnetic field thus creating quantum Hall edge channels. In electrostatically gapped bilayer graphene intriguingly, even in the absence of a magnetic field topologically protected electronic states can emerge at naturally occurring stacking domain walls. While individually both types of topologically protected states have been investigated, their intriguing interplay remains poorly understood. Here, we focus on the interplay between topological domain wall states and quantum Hall edge transport within the eight-fold degenerate zeroth Landau level of high-quality suspended bilayer graphene. We find that the two-terminal conductance remains approximately constant for low magnetic fields throughout the distinct quantum Hall states since the conduction channels are traded between domain wall and device edges. For high magnetic fields, however, we observe evidence of transport suppression at the domain wall, which can be attributed to the emergence of spectral minigaps. This indicates that stacking domain walls do potentially do not correspond to a topological domain wall in the order parameter.