Programme

O.2 -- Oral

Date: Friday, 24 November 2017

Time: 11:40 - 12:00

Quantum transport in nanojunctions with time-varying components

Eduardo C. Cuansing

Institute of Mathematical Sciences and Physics, University of the Philippines, Los Baños, Laguna 4031, Philippines

We study the transport of electrons and the resulting electron current in nanojunctions where time-varying components are present. In the first device, we allow the gate potential to vary in time. The second device is attached to heat baths and we incorporate electron-phonon interactions. In the third device, a photon beam is incident on the channel. We use the nonequilibrium Green's functions technique to calculate the electron current flowing across the devices. In the nonequilibrium Green's functions technique, we are able to express the Green's functions, via a perturbative expansion, in terms of integrals of steady-state Green's functions. In turn, these steady-state Green's functions can be expressed in terms of integrals of equilibrium Green's functions. Equilibrium Green's functions are calculated from the equations of motion of the particles. Nonequilibrum and steady-state Green's functions are then calculated using numerical integration. We find that in all three devices the current takes time to react whenever there is a sudden, non-adiabatic, change. The current then overshoots, oscillates, and eventually settles down to a steady value. In the device where there is a changing gate potential, the current is either amplified or attenuated depending on the sign of the gate potential. In the device that is coupled to heat baths, the electron-phonon interaction in the channel is switched on suddenly. We find that the averaged current across the device is less than the non-interacting case, indicating that the interaction acts as a drag to the electron flow. In the device where a photon beam is impinging on the channel, the current can be attenuated or amplified depending on the frequency of the impinging photon.

Presenter: Eduardo C. Cuansing

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