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

Abstract

We report from first principles, the possibility of reversible onset of topological insulator(TI) phase in heavier hydrogenated Xenes (Xane), namely, germanane and stanane, exclusively through in-plane electro-mechanical actuation. It is found possible to systematically induce robust uniaxial strain through non-uniform application of electric field in the plane of monolayers, as possible through application of in-homogeneous bias at gates of realizable length-scales embedded underneath. Electrically induced strain causes substantial lowering of band-gap across all Xanes, eventually evolving through weak followed by strong topologically insulating phases beyond a threshold degree of bias in-homogeneity in heavier Xanes, promisingly within the range of bias sustained by the monolayers. In case of nano-ribbons of these Xanes, bias applied in-homogeneously across width promises switchable emergence of TI phase over a fraction of width and topologically protected interface states localizable anywhere across the half-width of the ribbon. The demonstrated electro-mechanical actuation and the associated topological tuning of band-structure, thematically verified in gapped graphene based representative systems within the Kane-Mele model at half-filling, should be possible in the broader class of two dimensional covalent networks made of elements of the p-block.