Generalized input-output method to quantum transport junctions. II. Applications

We apply our generalized input-output method (GIOM), introduced in the previous paper of this series, to prototype molecular junction models describing vibrationally coupled electron transport. In short junctions where analytic treatments are available, we show that the charge current obtained by the GIOM reduces to known limits and reasonably agrees with exact numerical simulations (when available). For extended junctions, we numerically reveal that the current displays a turnover from phonon-assisted to phonon-suppressed transport as a function of electronic and vibrational parameters. As an additional application, we consider a cavity-coupled molecular junction. Here we identify a cavity-induced suppression of charge current in the single-site case, and observe the coexistence of phononic and photonic sidebands in the current-voltage characteristics when both strong light-matter interaction and electron-vibration coupling are present. Together with the first paper of this series, we demonstrate that the input-output framework, which is normally employed in quantum optics, can serve as a powerful and feasible tool in the realm of electron transport junctions.