Ladder network as a mesoscopic switch: An exact result

We investigate the possibilities of a tight binding ladder network as a mesoscopic switching device. Several cases have been discussed in which any one or both the arms of the ladder can assume random, ordered or quasiperiodic distribution of atomic potentials. We show that, for a special choice of the Hamiltonian parameters it is possible to prove exactly the existence of mobility edges in such a system, which plays a central role in the switching action. We also present numerical results for the two-terminal conductance of a general model of a quasiperiodically grown ladder which support the general features of the electron states in such a network. The analysis might be helpful in fabricating mesoscopic or DNA switching devices.