Giant intrinsic photoresponse in pristine graphene

• Main Authors: Ma, Qiong, Lui, Chun Hung, Song, Justin Chien Wen, 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
• Other Authors: School of Physical and Mathematical Sciences
• Format: Article
• Language: English
• Published: 2020
• Subjects: Science::Physics; Graphene; Electrons
• Online Access: https://hdl.handle.net/10356/138037
• Institution: Nanyang Technological University

When the Fermi level is aligned with the Dirac point of graphene, 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 photocurrent in graphene, which occurs in a different parameter regime from all the previously observed photothermoelectric or photovoltaic photocurrents in graphene12-20: 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.