  Topological insulators and D-brane charges in string theory can both be
classified by the same family of groups. In this paper, we extend this
connection via a geometric transform, giving a novel duality of topological
insulators which can be viewed as a condensed matter analog of T-duality in
string theory. For 2D Chern insulators, this duality exchanges the rank and
Chern number of the valence bands.
