Ultrafast Strong-Field Tunneling Emission in Graphene Nanogaps

Byung Hee Son¹, Hawn Sik Kim¹, Ji-Yong Park¹, Soonil Lee¹, Doo Jae Park^2*, 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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