Engineering of Chern insulators through defects

Impurities embedded in electronic systems induce bound states which can hybridize and lead to impurity bands. Recently, doping of insulators with impurities has been identified as a promising route towards engineering electronic topological states of matter. We illustrate how to engineer Chern insulators starting from a three-dimensional topological insulator with a gapped surface that is intentionally doped with magnetic impurities. The main advantage of the protocol is that it is robust and independent of details, always leading to a Chern insulator supporting a topological phase with Chern number one.