Tuning of electron transport through a quantum wire: An exact study

We explore electron transport properties in a quantum wire attached to two metallic electrodes. A simple tight-binding model is used to describe the system and the coupling of the wire to the electrodes (source and drain) is treated through Newns-Anderson chemisorption theory. In our present model, the site energies of the wire are characterized by the relation $\epsilon_i=W\cos(i \lambda^{\nu}\pi)$ where $W$, $\lambda$, $\nu$ are three positive numbers. For $\nu=0$, the threshold bias voltage of electron conduction across the bridge can be controlled very nicely by tuning the strength of the potential $W$. On the other hand, for $\nu \ne 0$, the wire becomes an aperiodic one and quite interestingly we see that, for some special values of $\nu$, the system exhibits a {\em metal-insulator} transition which provides a significant feature in this particular study. Our numerical results may be useful for fabrication of efficient switching devices.