title: Mechanism and modulation of terahertz generation from a semimetal--graphite.
abstract: Semi-metals might offer a stronger interaction and a better confinement for terahertz wave than semiconductors, while preserve tunability. Particularly, graphene-based materials are envisioned as terahertz modulators, filters and ultra-broadband sources. However, the understanding of terahertz generation from those materials is still not clear, thus limits us recognizing the potential and improving device performances. Graphite, the mother material of graphene and a typical bulk semi-metal, is a good system to study semi-metals and graphene-based materials. Here we experimentally modulate and maximize the terahertz signal from graphite surface, thus reveal the mechanism--surface field driving photon induced carriers into transient current to radiate terahertz wave. We also discuss the differences between graphite and semiconductors; particularly graphite shows very weak temperature dependency from room temperature to 80 °C. Above knowledge will help us understand terahertz generations, achieve maximum output and electric modulation, in semi-metal or graphene based devices.
authors.affiliation: Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190.
authors.forename: Tong
authors.initials: T
authors.lastname: Ye
authors.affiliation: Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190.
authors.forename: Sheng
authors.initials: S
authors.lastname: Meng
authors.affiliation: Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190.
authors.forename: Jin
authors.initials: J
authors.lastname: Zhang
authors.affiliation: Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190.
authors.forename: Yiwen
authors.initials: Y
authors.lastname: E
authors.affiliation: School of Science, Minzu University of China, Beijing, 100081.
authors.forename: Yuping
authors.initials: Y
authors.lastname: Yang
authors.affiliation: Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190.
authors.forename: Wuming
authors.initials: W
authors.lastname: Liu
authors.affiliation: Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190.|Cooperative Innovation Centre of Terahertz Science, Chengdu, Sichuan, 610054.
authors.forename: Yan
authors.initials: Y
authors.lastname: Yin
authors.affiliation: Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190.|Cooperative Innovation Centre of Terahertz Science, Chengdu, Sichuan, 610054.
authors.forename: Li
authors.initials: L
authors.lastname: Wang