Interaction of moire-induced quantum Hall channels in a locally gated graphene junction

TL;DR

This study investigates a novel p-n junction in aligned graphene lacking a band gap or zLL, revealing how van Hove singularities influence quantum Hall edge channel interactions under magnetic fields.

Contribution

It introduces a new type of p-n junction in aligned graphene without a band gap or zLL, highlighting the role of van Hove singularities in quantum Hall edge channel interactions.

Findings

Van Hove singularity emerges at p-n junctions under magnetic fields.

Magnetic breakdown occurs due to doping inversion near the secondary Dirac point.

Interactions between p-type and n-type QH edge channels are influenced by vHS.

Abstract

Manipulating electron quantum 1D channels is an important element in the field of quantum information due to their ballistic and phase coherence properties. In GaAs and graphene based two dimensional gas systems, these edge channels have been investigated with both integer and fractional quantum Hall effects, contributing to the realization of electron interferometer and anyon braiding. Often, at the p-n junction in the quantum Hall (QH) regime, the presence of a depletion region due to a band gap or the formation of gaps between the zeroth Landau levels (zLL) suppresses interaction between the co-propagating edge channels of opposing doping regimes and helps to preserve the phase coherence of the channels. Here, we observe a new type of p-n junction in hexagonal boron nitride aligned graphene that lacks both the zLL and band gap. In this system, a van Hove singularity (vHS) emerges at the p-n junctions under magnetic fields of several Tesla, owing to the doping inversion near the secondary Dirac point. By fabricating devices with independently tunable global bottom and local top gates, we enable the study of interactions between p-type and n-type QH edge channels through magnetic breakdown associated with the vHS. These findings provide valuable insights into the interactions of superlattice-induced QH edge channels in hBN-aligned graphene.