title: Tunnelling current-voltage characteristics of Angstrom gaps measured with terahertz time-domain spectroscopy.
abstract: Quantum tunnelling becomes inevitable as gap dimensions in metal structures approach the atomic length scale, and light passing through these gaps can be used to examine the quantum processes at optical frequencies. Here, we report on the measurement of the tunnelling current through a 3-Å-wide metal-graphene-metal gap using terahertz time-domain spectroscopy. By analysing the waveforms of the incident and transmitted terahertz pulses, we obtain the tunnelling resistivity and the time evolution of the induced current and electric fields in the gap and show that the ratio of the applied voltage to the tunnelling current is constant, i.e., the gap shows ohmic behaviour for the strength of the incident electric field up to 30 kV/cm. We further show that our method can be extended and applied to different types of nanogap tunnel junctions using suitable equivalent RLC circuits for the corresponding structures by taking an array of ring-shaped nanoslots as an example.
authors.affiliation: Department of Physics and Astronomy and Center for Atom Scale Electromagnetism, Seoul National University, Seoul 08826, Korea.
authors.forename: Joon-Yeon
authors.initials: JY
authors.lastname: Kim
authors.affiliation: Department of Physics and Department of Energy Systems Research, Ajou University, Suwon 16499, Korea.
authors.forename: Bong Joo
authors.initials: BJ
authors.lastname: Kang
authors.affiliation: Department of Physics and Astronomy and Center for Atom Scale Electromagnetism, Seoul National University, Seoul 08826, Korea.
authors.forename: Young-Mi
authors.initials: YM
authors.lastname: Bahk
authors.affiliation: Graphene Research Institute and Department of Physics, Sejong University, Seoul 05006, Korea.
authors.forename: Yong Seung
authors.initials: YS
authors.lastname: Kim
authors.affiliation: Department of Nanoscale Semiconductor Engineering and Hanyang University, Seoul 04763, Korea.
authors.forename: Joohyun
authors.initials: J
authors.lastname: Park
authors.affiliation: Department of Physics and Department of Energy Systems Research, Ajou University, Suwon 16499, Korea.
authors.forename: Won Tae
authors.initials: WT
authors.lastname: Kim
authors.affiliation: Department of Physics and Astronomy and Center for Atom Scale Electromagnetism, Seoul National University, Seoul 08826, Korea.
authors.forename: Jiyeah
authors.initials: J
authors.lastname: Rhie
authors.affiliation: Department of Physics and Astronomy and Center for Atom Scale Electromagnetism, Seoul National University, Seoul 08826, Korea.
authors.forename: Sanghoon
authors.initials: S
authors.lastname: Han
authors.affiliation: Department of Nanoscale Semiconductor Engineering and Hanyang University, Seoul 04763, Korea.|Division of Materials Science and Engineering, Hanyang University, Seoul 04763, Korea.
authors.forename: Hyeongtag
authors.initials: H
authors.lastname: Jeon
authors.affiliation: Department of Physics and Astronomy and Center for Theoretical Physics, Seoul National University, Seoul 08826, Korea.
authors.forename: Cheol-Hwan
authors.initials: CH
authors.lastname: Park
authors.affiliation: Department of Physics and Department of Energy Systems Research, Ajou University, Suwon 16499, Korea.
authors.forename: Fabian
authors.initials: F
authors.lastname: Rotermund
authors.affiliation: Department of Physics and Astronomy and Center for Atom Scale Electromagnetism, Seoul National University, Seoul 08826, Korea.
authors.forename: Dai-Sik
authors.initials: DS
authors.lastname: Kim