DOE OSTI2018
When the Fermi level is aligned with the Dirac point of gra-phene, reduced charge screening greatly enhances electron–electron scattering1–5. In an optically excited system, the kinematics of electron–electron scattering in Dirac fermions is predicted to give rise to novel optoelectronic phenomena6–11. In this paper, we report on the observation of an intrinsic pho-tocurrent in graphene, which occurs in a different parameter regime from all the previously observed photothermoelectric or photovoltaic photocurrents in graphene12–20: the photo-current emerges exclusively at the charge neutrality point, requiring no finite doping. Unlike other photocurrent types that are enhanced near p–n or contact junctions, the photo-current observed in our work arises near the edges/corners. By systematic data analyses, we show that the phenomenon stems from the unique electron–electron scattering kinemat-ics in charge-neutral graphene. Our results not only high-light the intriguing electron dynamics in the optoelectronic response of Dirac fermions, but also offer a new scheme for photodetection and energy harvesting applications based on intrinsic, charge-neutral Dirac fermions.
solar (photovoltaic), solid state lighting, photos↗