Mechanical effect on the electronic properties of molecular wires

The coupling of mechanical-electronic properties of one-dimensional (1D) conducting linear conjugated molecules (molecular wires) is investigated. An extended Su-Schrieffer-Heeger Hamiltonian considering the effect of a mechanical stretch is developed. It is found, based on this extended Hamiltonian, that the π-electron band gap of pristine polyacetylene decreases with the increase in the strength of the stretch, indicating the role of stretch to change a transition of electrical properties of polyacetylene from insulator to semiconductor. The dimerization amplitudes decrease with the increase in the degree of stretch, indicating the role of the stretch to induce a conformation change from dimerized to undimerized structure. The effect of electron-phonon coupling on the speed of sound in polyacetylene is also determined, using a simple step, and the same result as the commonly accepted one is obtained. The electron transfer rates in a donor-bridge-acceptor system are found to increase with the application of a stretch. This result suggests an alternative scheme to enhance the conductivity of a conjugated chain instead of by doping or the use of transversal electric field. The possible application of molecular wires as a molecules balance is also outlined.