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

TL;DR

This paper demonstrates that in-plane electro-mechanical actuation can reversibly induce topological insulator phases in hydrogenated Xenes like germanane and stanane, enabling tunable topological properties via electric field-induced strain.

Contribution

It introduces a method for reversible topological phase switching in heavier hydrogenated Xenes through in-plane electric field-induced strain, verified by first-principles calculations.

Findings

Electric field can induce uniaxial strain in Xenes.

Strain causes band-gap reduction and topological phase transition.

Switchable topological states are achievable in nano-ribbons.

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.