Introduction. Lateral junctions are a useful tool for manipulating and studying topological edge modes. In quantum Hall samples, these junctions have enabled an understanding of equilibration amongst chiral edge states in the unipolar and bipolar regimes1,2,3,4,5,6,7,8,9. Thus far, studies of lateral junctions have been mostly limited to topologically trivial materials in the quantum Hall regime, such as GaAs/AlGaAs quantum wells1,2,8 and graphene4,5,6,7. Two-dimensional topological insula...