We outline an approach to endow a plain vanilla material with topological properties by creating topological bands in stacks of manifestly nontopological atomically thin materials. The approach is illustrated with a model system comprised of graphene stacked atop hexagonal-boron-nitride. In this case, the Berry curvature of the electron Bloch bands is highly sensitive to the stacking configuration. As a result, electron topology can be controlled by crystal axes alignment, granting a practical route to designer topological materials. Berry curvature manifests itself in transport via the valley Hall effect and long-range chargeless valley currents. The non-local electrical response mediated by such currents provides diagnostics for band topology.
@article{arxiv.1404.4019,
title = {Topological Bloch Bands in Graphene Superlattices},
author = {Justin C. W. Song and Polnop Samutpraphoot and Leonid S. Levitov},
journal= {arXiv preprint arXiv:1404.4019},
year = {2015}
}