Ultrafast anisotropic exciton transport in phosphorene.

Phosphorene is a two-dimensional (2D) material exhibiting strong in-plane structural anisotropy. In this work, we investigate the influence of structural anisotropy on the optics, dynamics, and transport of excitons in phosphorene by combining microscopic many-body theory with first principles calculations. Our framework offers a complete and material specific description of the excitonic properties of phosphorene, including exciton states and exciton-phonon interactions, which allow us to quantitatively evaluate the optical absorption spectra, exciton relaxation, and exciton transport, revealing direction-dependent characteristics. Interestingly, we identify the critical role of long-range exchange interactions, which significantly enhance the anisotropy of exciton diffusion, particularly at low temperatures. Our work provides fundamental insights into exciton dynamics in an intrinsically anisotropic 2D material, offering guiding principles for the design of next-generation optoelectronic devices.