Robust electro-mechanical actuation in hydrogenated Xenes leading to reversible topological transition

We report, from first principles, the possibility of reversible onset of the topological insulator (TI) phase in heavier Xanes exclusively through in-plane electro-mechanical actuation. It is found that it is possible to systematically induce robust uniaxial strain through non-uniform application of bias using gates of realizable length-scales. This causes substantial lowering of the band-gap across all Xanes, eventually evolving through weak and strong topologically insulating phases in heavier Xanes, namely germanane and stanane, promisingly within the range of bias sustained by the monolayers. In the case of nano-ribbons of heavier Xanes, bias applied inhomogeneously across the width promises switchable emergence of the TI phase over a fraction of the width and thereby topologically protected interface states, which can be chosen to localize anywhere across the half-width of the ribbon. The demonstrated electro-mechanical actuation and the associated topological tuning of the band-structure, thematically verified in gapped-graphene-based representative systems within the Kane-Mele model with collinear spins, should be possible in the broader class of two-dimensional covalent networks made of elements from the p-block.