  We theoretically investigate the quantum reflection of different atoms by
two-dimensional (2D) materials of the graphene family (silicene, germanene, and
stanene), subjected to an external electric field and circularly polarized
light. By using Lifshitz theory to compute the Casimir-Polder potential, which
ensures that our predictions apply to all regimes of atom-2D surface distances,
we demonstrate that the quantum reflection probability exhibits distinctive,
unambiguous signatures of topological phase transitions that occur in 2D
materials. We also show that the quantum reflection probability can be highly
tunable by these external agents, depending on the atom-surface combination,
reaching a variation of 40% for Rubidium in the presence of a stanene sheet.
Our findings attest that not only dispersive forces play a crucial role in
quantum reflection, but also that the topological phase transitions of the
graphene family materials can be comprehensively and efficiently probed via
atom-surface interactions at the nanoscale.
