Resonant second-harmonic generation in a ballistic graphene transistor with an ac-driven gate

Abstract

We report a theoretical study of time-dependent transport in a ballistic graphene field effect transistor. We develop a model based on Floquet theory describing Dirac electron transmission through a harmonically driven potential barrier. Photon-assisted tunneling results in excitation of quasibound states at the barrier. Under resonance conditions, the excitation of the quasibound states leads to promotion of higher-order sidebands and, in particular, an enhanced second harmonic of the source-drain conductance. The resonances in the main transmission channel are of the Fano form, while they are of the Breit-Wigner form for sidebands. For weak ac drive strength Z 1 , the dynamic Stark shift scales as Z 4 1 , while the resonance broadens as Z 2 1 . We discuss the possibility of utilizing the resonances in prospective ballistic high-frequency devices, in particular frequency doublers operating at high frequencies and low temperatures.

Nonlinear response of a ballistic graphene transistor with an ac-driven gate: High harmonic generation and terahertz detection

“…that we studied for U (x) = 0 in Ref. 37. In that case, the bound state does not affect dc transport properties, but can be excited by ac drive.…”

“…The driving frequency, Ω, is between 0.4-40 meV for the THz frequency range 0.1 − 10 THz. The drive strength Z 1 , for Z 1 ∼ 1, corresponds to a voltage of the order of a meV on the top gate for typical gate lengths (see the estimate in our previous paper 37 ). Finally, in the following we assume that temperature is the smallest energy scale (we put T = 0).…”

Shot noise in a harmonically driven ballistic graphene transistor

“…We shall focus on the shot noise at zero temperature in parameter regimes corresponding to the resonances discussed in detail in Ref. 46 and 47. The device depicted in Fig.…”

“…In high-frequency devices, time-dependent electric field of frequency Ω induces sidebands in energy space separated by multiples of energy quantum Ω. Interference of quasiparticle scattering paths between the sidebands is therefore important [43][44][45][46][47] . In our previous papers 46,47 we examined in detail the linear conductance of a ballistic graphene transistor with an ac-driven top gate.…”

“…Interference of quasiparticle scattering paths between the sidebands is therefore important [43][44][45][46][47] . In our previous papers 46,47 we examined in detail the linear conductance of a ballistic graphene transistor with an ac-driven top gate. Scattering via quasibound states under the gate induces resonances in selected sideband amplitudes, and we have identified two resonant scattering mechanisms: double barrier tunnelling (between contacts and top barrier) for high doping of the contacts and Breit-Wigner/Fano resonances for low doping.…”