Manipulating Wannier-Mott Intralayer Exciton, Radiative Lifetime and Rashba Spin Splitting in Sb-Based Chalcogenide Janus Monolayers

We have envisaged the effect of chalcogen to manipulate the Rashba splitting strength and the corresponding spin-texture along with the Wannier-Mott exciton radiative lifetime in antimony (Sb) based Janus SbXI (X = S, Se, Te) monolayers. The structural, electronic, spin-texture evolution and excited state properties of the three monolayer systems are systematically investigated based on the electronic structure calculations by combining density functional theory (DFT) and many-body perturbation theory (MBPT) formalisms. The synergistic effect of broken inversion symmetry and strong spin–orbit coupling (SOC) in the monolayers, gives rise to different Rashba spin splitting strength for different chalcogen constituents, while all of them are found to be indirect band gap semiconductors. The excited state properties along with the optical absorption spectra and exciton binding energies and corresponding radiative lifetime are determined by solving the Bethe–Salpeter equation (BSE) on top of the G0W0 approximation. The optical absorption spectra reveal the excitonic states within the quasi-particle band gap. Due to the reduced dielectric screening in these two-dimensional (2D) Janus monolayers, we observed strong exciton binding energies and long radiative lifetimes for the first bright excitons, while Wannier-Mott type intralayer excitonic features mostly prevail throughout the investigation. Our proposed tuning mechanism of Rashba spin splitting and corresponding spin texture along with the intralayer excitonic radiative lifetime in these emerging Janus monolayers would position them as promising candidates for next generation optoelectronic and spintronic devices.