Electronic transport of benzothiophene-based chiral molecular solenoids studied by theoretical simulations

By the density-functional-derived tight-binding method, the electronic transport properties of two types of benzothiophene-based molecular wires, i.e., the linear and helical molecular wires have been investigated. In the molecular bridge system where these molecules are connected to the gold electrodes by S–Au bonds, the transmission peaks are found to lie at the energies somewhat lower than 0.5 eV below the Fermi level for both cases. Thus the conductances of both types of wires for the bias voltage less than 1.0 V are not so large without doping. Upon iodine doping, however, the new transmission peaks are found to appear around the Fermi level, particularly in the case of helical wires. It means that the conductances of the helical wires are expected to be improved dramatically by the chemical doping. Therefore, the doped helical molecular wires are predicted to work as molecular solenoids even under lower bias voltages. Next, the applicability of the current-induced magnetic field generated in such a molecular solenoid is considered. As an example, we propose a novel helical molecule where the hydrogen atoms connected to the inner C–C bonds of the helix are substituted by some kind of radicals. In this case the current-induced field can control the alignment of the radical spin orientations.