Strong interlayer excitons in PtSe2/ZrS2 van der Waals heterobilayer

Capturing interlayer excitons with large binding energy plays a pivotal role in exploring the quantum Bose gas and developing excitonic devices at high temperature. In this work, we combine first-principles Kohn–Sham density functional theory and many-body perturbation theory to investigate the electronic and excited-state properties of two-dimensional van der Waals heterobilayer PtSe2/ZrS2, with the consideration of spin–orbit coupling. We find that the PtSe2/ZrS2 heterobilayer possesses a strong interlayer interaction and exhibits a type-II band alignment. We obtain the optical absorption spectrum by solving the Bethe–Salpeter equation with the inclusion of electron-hole interaction and observe emerged absorption peaks in the low-energy region compared to their constituent monolayers. According to the layer-resolved band structure and the interband transition weights in reciprocal space, we further confirm that these excitons are spatially separated into different constituent layers, featuring the landscape of interlayer excitons. Importantly, the binding energy for the lowest-energy interlayer exciton is estimated as large as 350 (meV), establishing PtSe2/ZrS2 as a promising candidate toward the realization of room temperature coherent phenomena and for the development of signal processing devices based on excitons.