Polaronic signatures in pristine phosphorene

We investigate polaronic effects in a monolayer black phosphorus (or phosphorene) due to the charge carrier-intrinsic phonons interaction. We employ a microscopic model to describe vibrational spectra and electron-phonon interactions within the tight-binding approach. Our adiabatic solution for polarons suggests the critical coupling constant of λc=3.0 for polaron self-trapping in this anisotropic material. We report nonadiabatic calculations for the band-gap renormalization and the effective mass enhancement as a function of temperature and a range of electron-phonon coupling strengths. Our results demonstrate a surprising large band-gap renormalization, even for the lower bound of the electron-phonon coupling strength reported in the literature. We find that optical phonons give the dominant contributions to the polaronic effect.