Electronic transport in a shuttle with a discrete energy spectrum

Artikel i vetenskaplig tidskrift, 2009

We present a multiscale approach for a molecular nanoelectromechanical shuttle, which takes into account the discrete energy levels and realistic orbitals of a specific molecular system. We deploy a Cu13 cluster as a central island and describe the electrodes within the jellium model. The shuttling features are then examined for a wide spectrum of bias voltages. The microscopic data of the cluster are obtained with density functional theory (DFT) while the macroscopic part combines stochastic charge dynamics, based on the microscopically evaluated tunnelling rates, with Newtonian dynamics. We find four transport regimes within the analysed bias voltage interval: a blocked regime (Vbias≤ 2 V), a pure shuttling regime (3 V ≤Vbias≤ 4 V), a mixed regime (5 V ≤Vbias≤ 6 V) and a direct tunnelling regime (Vbias≥7 V). In the two latter cases, the shuttling motion leads to a reduced current as compared to an island with a fixed position. The transport characteristics are strongly coupled to the availability of energetically allowed channels and the system therefore depends strongly on the microscopic details and bias voltages. For the setup at hand, however, the shuttling transport of one electron is ubiquitous and stable for all but the blocked regime.