Engineering a topological phase transition in β-InSe via strain

We report that beta-InSe endowed with external strain realizes a novel three dimensional topological insulator (TI) by ab initio calculations. We predicate that the promising topological non-trivial state can be observed in an accessible temperature regime in beta-InSe for its large spin-orbital band gap up to 121 meV. Specifically, unlike in previous literature where the band inversion (BI) in TIs is induced using heavy elements that have strong spin-orbital coupling (SOC), we provide a remarkable blueprint for stabilizing BI solely by mechanical deformation so that beta-InSe could display BI even without considering SOC. Nevertheless, SOC is still needed to create a band gap at the crossing point by breaking the incompatibility symmetry of the inverted bands.X