Casimir–Polder interaction between an atom and a Chern insulator: topological signature and long-range repulsion

We consider the Casimir–Polder interaction between a two-level atomic system and a Chern insulator for both the resonant and nonresonant channels. For a right circularly polarized excited atomic state near a Chern insulator with a negative Chern number C, the resonant Casimir–Polder force can be monotonically repulsive over a large range of separations. In the presence of the same Chern insulator, a right circularly polarized metastable atomic state is expected to experience a repulsive nonresonant Casimir–Polder force over a certain range of atom-surface separations in the far-field region. At still greater separations, the nonresonant Casimir–Polder force is expected to become attractive and exhibit a topological signature, being proportional to [Formula: see text], where [Formula: see text] is the fine-structure constant.