Transport Properties in a One-Dimensional Chain with Randomly Side-Coupled Impurities

We investigate the transport properties of a one-dimensional (1D) chain with randomly side-coupled impurities. By using the transfer matrix technique, we present numerical results of the transmission coefficient as a function of the electron energy. It is found that an extended state will be shown in such a random 1D system if the impurities are side-coupled to the chain with not only the nearest-neighbouring bonds but also the next-nearest-neighbouring-bonds. We present an analytic expression for the energy of this extended state, which is determined by the strength of the nearest and next-nearest couplings between the impurities and the chain. The obtained results can be used to explain the transport properties of DNA chains and other quasi-1D organic structures.