Ab initio investigation on exciton-phonon interaction and exciton mobility in black phosphorene

Black phosphorene (BP) is an emerging two-dimensional material that has potentially wide applications in nano-and optoelectronics. Despite the strong excitonic effects observed in few-layer BP, there is still a lack of understanding regarding exciton-phonon (ex-ph) interaction and exciton mobility. In this work, using GW plus real-time Bethe-Salpeter equation approach, it is revealed that the out-of-plane acoustic phonon mode ZA, and the optical phonon modes A1g and A2g couple strongly with the exciton. Among them, the A2g mode has a uniquely significant influence on the oscillator strength. Driven by these ex-ph interactions, the exciton becomes more localized accompanied with strengthened binding and the absorption spectrum undergoes a notable renormalization at 300 K. In the framework of deformation potential theory, the exciton mobility of monolayer BP (MLBP) is found to be largely suppressed compared to the free-charge carriers, showing quasi-one-dimensional character. This work provides rich knowledge of ex-ph interaction and exciton mobility in MLBP at the ab initio level, offering insights for the understanding and controlling the exciton behavior in BP-based devices.