Topological phase transition in GeSnH₂ induced by biaxial tensile strain: A tight-binding study

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.