When the Fermi level is aligned with the Dirac point of graphene, reduced charge screening greatly enhances electron–electron scattering^1,2,3,4,5. In an optically excited system, the kinematics of electron–electron scattering in Dirac fermions is predicted to give rise to novel optoelectronic phenomena^{6,7,8,9,10,11}. In this paper, we report on the observation of an intrinsic photocurrent in graphene, which occurs in a different parameter regime from all the previously observed photothermoelectric or photovoltaic photocurrents in graphene^{12,13,14,15,16,17,18,19,20}: the photocurrent 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 photocurrent 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 kinematics in charge-neutral graphene. Our results not only highlight 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.

当费米能级与石墨烯的狄拉克点对准时，减少的电荷屏蔽会大大增强电子，电子的^1,2,3,4,5散射。在光激发系统中，狄拉克费米子中电子-电子散射的运动学预计会引起新的光电现象^{6,7,8,9,10,11}。在本文中，我们报告了对石墨烯固有光电流的观察，该电流发生在与石墨烯中所有先前观察到的光热电或光伏光电流不同的参数范围内^{12,13,14,15,16,17,18,19， 20}：光电流仅在电荷中性点出现，不需要有限的掺杂。与在p–n或接触结附近增强的其他光电流类型不同，在我们的工作中观察到的光电流出现在边缘/角附近。通过系统的数据分析，我们表明该现象源于电荷中性石墨烯中独特的电子-电子散射运动学。我们的结果不仅突出了狄拉克费米子在光电响应中令人着迷的电子动力学，而且为基于内在电荷中性狄拉克费米子的光检测和能量收集应用提供了新的方案。