Single-band Hubbard model for the transport properties in bistable organic/metal nanoparticle/organic devices

The transport properties of bistable organic/metal nanoparticle/organic devices are investigated within the single-band Hubbard model. The effect of two electrodes on the molecules with the nanoparticles is taken into account by using the Newns' chemisorption theory. The Coulomb interactions between the electrons in the Hubbard model are treated by the spectral density approach. The transmission probabilities of the system are calculated as a function of the energy, the organic layers' thickness, and the hopping term for the organic layers. At small bias, the transmission probability is small near the Fermi level if no charges are trapped in the system, which corresponds to the low-conductance state of the device. Above a threshold bias, the electrons within the nanoparticles will tunnel resonantly from one side to the other side, and the resulting positive-negative charges are trapped at both sides of the nanoparticle layer, in which case the transmission probability increases tremendously near the Fermi level, resulting in the high-conductance state. The layer-dependent densities of states are used to investigate the phenomena in detail. The transmission probability decreases exponentially as the thickness of the organic layers increases.