Current Optics and Photonics

Optical Society of Korea (한국광학회)
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Theoretical Study of the Strong Field Emission of Electrons inside a Nanogap Due to an Enhanced Terahertz Field

  • Received : 2018.11.02
  • Accepted : 2018.11.13
  • Published : 2018.12.25
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Abstract

We report the development of a theoretical model describing the strong field tunneling of electrons in an extremely small nanogap (having a width of a few nanometers) that is driven by terahertz-pulse irradiation, by modifying a conventional semiclassical model that is widely applied for near-infrared wavelengths. We demonstrate the effects of carrier-envelope phase difference and strength of the incident THz field on the tunneling current across the nanogap. Additionally, we show that the dc bias also contributes to the generation of tunneling current, but the nature of the contribution is completely different for different carrier-envelope phases.

Keywords

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FIG. 1. (Color online) Schematic diagram of electron tunneling in the vicinity of vacuum-level modification associated with a THz pulse, for (a) positive phase and (b) negative phase.

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FIG. 2. (Color online) Calculated kinetic-energy distribution as a function of time (black curve), and tunneling current as a function of time (red curve), for a carrier-envelope phase (CEP) difference of (a) zero and (b) π/2. (c) Net tunneling current as a function of CEP difference. (d) Polar plot of the absolute value of the net tunneling current.

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FIG. 3. (Color online) Calculated kinetic-energy spectrum for a CEP difference of (a) zero, (b) π/2, (c) π, and (d) 3π/2.

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FIG. 4. (Color online) Log-log plot of calculated tunneling current as a function of THz field amplitude.

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FIG. 5. (Color online) Calculated kinetic-energy distribution as a function of time (black curve), and tunneling current as a function of time (red curve), for a THz field amplitude of (a) 33.3 kV/cm and (b) 137 kV/cm. Calculated kinetic-energy spectrum for a THz field amplitude of (c) 33.3 kV/cm and (d) 137 kV/cm.

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FIG. 6. (Color online) Schematic diagram of dc bias contribution plus THz electric field, for a CEP difference of (a) zero and (b) π. (c) Log-log plot of calculated tunneling current as a function of dc bias, for a CEP difference of zero (black solid square), π/2 and 3π/2 (blue open square), and π (red solid circle); (inset) linear plot of calculated tunneling current.

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FIG. 7. (Color online) Calculated kinetic-energy distribution as a function of time (black curve), and tunneling current as a function of time (red curve), with 2 V applied bias, for a carrier-envelope phase (CEP) difference of (a) zero, (b) π/2, and (c) π. Calculated kinetic-energy spectrum for a CEP difference of (d) zero, (e) π/2, and (f) π.

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