Anisotropic Interlayer Exciton in GeSe/SnS van der Waals Heterostructure.

Stacking two or more two-dimensional materials to form a heterostructure is becoming the most effective way to generate new functionalities for specific applications. Herein, using GW and Bethe-Salpeter equation simulations, we demonstrate the generation of linearly polarized, anisotropic intra- and interlayer excitonic bound states in the transition metal monochalcogenide (TMC) GeSe/SnS van der Waals heterostructure. The puckered structure of TMC results in the directional anisotropy in band structure and in the excitonic bound state. Upon the application of compressive/tensile biaxial strain dramatic variation (∓3%) in excitonic energies, the indirect-to-direct semiconductor transition and the red/blue shift of the optical absorption spectrum are observed. The variations in excitonic energies and optical band gap have been attributed to the change in effective dielectric constant and band dispersion upon the application of biaxial strain. The generation and control over the interlayer excitonic energies can find applications in optoelectronics and optical quantum computers and as a gain medium in lasers.