Coulomb drag in parallel nanowires

University essay from Lunds universitet/Fasta tillståndets fysik; Lunds universitet/Fysiska institutionen

Author: David Dai; [2020]

Keywords: Coulomb drag; nanowire; Physics and Astronomy;

Abstract: In this project the transport phenomenon Coulomb drag is studied in a 1D system comprised of two nanowires in parallel. Specifically, a driving current across the active wire generated a drag current in the passive wire, and we studied how Coulomb drag influenced both the driving and drag currents. The theoretical calculations used in this project are based on the approach made by Gurevich et al. [Coulomb drag in the ballistic electron transport regime, Journal of Physics: Condensed Matter 10, 1 (1998)]. The approach is to solve the Boltzmann transport equation describing the Coulomb drag using an iterative method. What is different in our approach is that we iterated until we found a converged solution unlike Gurevich et al. who only iterated once. We also calculated the change in the driving current due to Coulomb drag which was not made by Gurevich et al.. Our study showed that the drag current is linear as a function of applied bias voltage in both the passive and active wires in the small bias region. A non-linear drag current in the passive wire in the large bias regime where linear response theory no longer holds was also shown in our study. The temperature dependence of the drag and driving currents were also calculated. The results showed that the drag current generated in the passive wire has a linear temperature dependence while the temperature dependence of the current in the active wire was barely affected by the presence of Coulomb drag because the driving current is much larger than the generated drag current. We also found that the drag current has an exponential dependency of inter-wire separation distance, which coincides with the predictions of Gurevich et al. [Coulomb drag in the ballistic electron transport regime, Journal of Physics: Condensed Matter 10, 1 (1998)]. Lastly, our numerical calculations showed that the number of iterations required to reach a converged solution are few but increases if parameters corresponding to stronger electron-electron interaction are used.

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