Ma Qiong, Lui Chun Hung, Song Justin C W, Lin Yuxuan, Kong Jian Feng, Cao Yuan, Dinh Thao H, Nair Nityan L, Fang Wenjing, Watanabe Kenji, Taniguchi Takashi, Xu Su-Yang, Kong Jing, Palacios Tomás, Gedik Nuh, Gabor Nathaniel M, Jarillo-Herrero Pablo
Department of Physics, Massachusetts Institute of Technology, Cambridge, MA, USA.
Department of Physics and Astronomy, University of California, Riverside, CA, USA.
Nat Nanotechnol. 2019 Feb;14(2):145-150. doi: 10.1038/s41565-018-0323-8. Epub 2018 Dec 17.
When the Fermi level is aligned with the Dirac point of graphene, reduced charge screening greatly enhances electron-electron scattering. In an optically excited system, the kinematics of electron-electron scattering in Dirac fermions is predicted to give rise to novel optoelectronic phenomena. 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: 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齐时，电荷屏蔽的减弱会极大地增强电子 - 电子散射。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产生新的光电现象。在本文中，我们报告了在石墨烯中观察到的一种本征光电流，它出现在与石墨烯中所有先前观察到的光热电流或光伏光电流不同的参数范围内：该光电流仅在电荷中性点出现，无需有限掺杂。与在 p - n 或接触结附近增强的其他光电流类型不同，我们工作中观察到的光电流出现在边缘/角落附近。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光电响应中有趣的电子动力学，还为基于本征、电荷中性狄拉克费米子的光探测和能量收集应用提供了一种新方案。
