Interface dark excitons at sharp lateral two-dimensional heterostructures

Abstract

We study the dark excitons at the interface of a sharp lateral heterostructure of two-dimensional transition metal dichalcogenides (TMDs). By introducing a low-energy effective Hamiltonian model, we find the energy dispersion relation of exciton and show how it depends on the onsite energy of composed materials and their spin–orbit coupling strengths. It is shown that the effect of the geometrical structure of the interface, as a deformation gauge field (pseudo-spin–orbit coupling), should be considered in calculating the binding energy of exciton. By discretization of the real-space version of the dispersion relation on a triangular lattice, we show that the binding energy of exciton depends on its distance from the interface line. For exciton near the interface, the binding energy is equal to 0.36 eV, while for the exciton far enough from the interface, it is equal to 0.26 eV. Also, it has been shown that for a zigzag interface the binding energy increases by 0.34 meV compared to an armchair interface due to the pseudo-spin-orbit interaction (gauge filed). The results can be used for designing 2D-dimensional-lateral-heterostructure- based optoelectronic devices to improve their characteristics.