Ultrafast Strong-Field Tunneling Emission in Graphene Nanogaps
Byung Hee Son1, Hawn Sik Kim1, Ji-Yong Park1, Soonil Lee1, Doo Jae Park2*, Yeong Hwan Ahn1
1Department of Physics and Department of Energy Systems Research, Ajou University, Suwon 16499, Korea
2Department of Applied Optics and Physics, Hallym University, Chuncheon 24252, Korea
* Presenter:Doo Jae Park
We demonstrate subcycle electron pulse generation in a nanogap of graphene when irradiated by a femtosecond laser pulse in the near-infrared region (800 nm). A strong photo-induced emission was produced when the gap area was irradiated by the ultrashort pulse laser. The graphene, which has atomically sharp edges with the large damage threshold, enable us to achieve the strong tunneling regime for the subcycle field emission. The photo-induced signals exhibited an anomalous increase in nonlinear order as a function of incident pulse energy in the presence of static electric field. A dynamical analysis of tunneling electrons based on the semi-classical model, which considers the contribution from the recoil electrons, reproduced our observation successfully. The large field enhancement near the graphene edge enabled us to reach the deep tunneling regime with the extraordinary Keldysh parameter of 0.2 in the near-infrared region, which has not been accessible by the conventional metal nanostructures.

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