Band engineering aided by topological edge state proximity effects: Inducing antichirality in graphene

In this work we analyze infinite graphene nanoribbons subjected to nonuniform magnetic fields that produce topological domain walls in the quantum Hall regime. We show how the proximity between edge states from neighboring domains modifies the band structure due to the state coupling near the domain walls. The proximity-induced band deformations produce phenomena such as bulklike dispersion that coexist with Landau levels and valley-polarized current paths. It is shown that edge state coupling can be enhanced by continuously varying the magnetic field between two nontrivial topological phases. The mechanism by which neighboring edge states modify the band structure is addressed by tracking their wave functions over isolated bands and by analyzing the magnetic confinement potential near the domain wall. By calculating the local current density, we show that the coexistence of topological edge states with bulklike dispersion can lead to the appearance of antichirality, in which copropagating currents appear in the edges while the rest of the nanoribbon is occupied with bulk states. The appearance of antichirality is justified by comparing the proposed nonuniform magnetic field profile with an antichiral modified Haldane model. The relation between the proximity effects and quantum transport is explored by conductance calculations in a multiterminal setup using the Landauer-B"uttiker formalism.