Boundary Modes from Periodic Magnetic and Pseudomagnetic Fields in Graphene

TL;DR

This paper explores how periodic magnetic and pseudomagnetic fields in graphene create boundary modes with distinct topological properties, revealing new boundary spectra and valley-helical transport channels.

Contribution

It compares the effects of magnetic and pseudomagnetic fields on boundary modes in graphene, highlighting the topological classification and boundary phenomena.

Findings

Magnetic fields induce single counter-propagating modes on opposite edges.

Pseudomagnetic fields lead to pairs of modes on the same boundary.

Valley-helical transport channels can be realized and detected experimentally.

Abstract

Single-layer graphenes subject to periodic lateral strains are artificial crystals that can support boundary spectra with an intrinsic polarity. These are analyzed by comparing the effects of periodic magnetic fields and strain-induced pseudomagnetic fields that respectively break and preserve time-reversal symmetry. In the former case, a Chern classification of the superlattice minibands with zero total magnetic flux enforces {\it single} counter-propagating modes traversing each bulk gap on opposite boundaries of a nanoribbon. For the pseudomagnetic field, pairs of counter-propagating modes migrate to the {\it same} boundary where they provide well-developed valley-helical transport channels on a single zigzag edge. We discuss possible schemes for implementing this situation and their experimental signatures.