Topological phase transition in GeSnH${}_2$ induced by biaxial tensile strain: A tight-binding study

Abstract

An effective tight-binding (TB) Hamiltonian for monolayer GeSnH${}_2$ is proposed which has an inversion-asymmetric honeycomb structure. The low-energy band structure of our TB model agrees very well with previous {\it ab initio} calculations under biaxial tensile strain. We predict a phase transition upon 7.5\% biaxial tensile strain in agreement with DFT calculations. Upon 8.5\% strain the system exhibits a band gap of 134 meV, suitable for room temperature applications. The topological nature of the phase transition is confirmed by: 1)the calculation of the ${\mathbb{Z}}_2$ topological invariant, and 2)quantum transport calculations of disordered GeSnH${}_2$ nanoribbons which allows us to determine the universality class of the conductance fluctuations.

8 pages, 6 figures