Strain-engineered electronic and topological properties of bismuthene on SiC(0001) substrate

By combining density functional theory with low-energy effective Hamiltonian, we demonstrate strain-engineered electronic and topological properties of the recently synthesized two-dimensional (2D) bismuthene on SiC(0001) substrate. As bismuthene on SiC(0001) exhibits an indirect gap of 0.62 eV with nontrivial topology, we show that the band gap size can be further increased by an applied tensile strain, which follows a nearly linear fashion. Especially, with a tensile strain of 7%, the topological gap can be enhanced to an unprecedented value of 0.83 eV, originating from the different deformation potentials of the conduction band minimum principally contributed from p orbitals of Bi and valance band maximum from the hybridized states of Bi overlayer and SiC substrate. Moreover, we discuss the strength of spin-orbit coupling, in additional to the strain effect, in tuning the electronic structures and topological edge states. Our results suggest the promise of strain engineering in manipulating large-gap quantum spin Hall states on conventional semiconductor for practical dissipationless electronic transport and quantum information processing.