Multiple delocalization of electrons and persistent currents in random n-mer mesoscopic rings

We demonstrate that the electronic property of a mesoscopic ring can be alternatively tuned between metallic and insulative states by changing the Fermi level. The one-dimensional mesoscopic ring is constructed based on random n-mer model and threaded by magnetic flux. Multiple localization-delocalization transitions of electrons have been found. When the Fermi level approaches the resonant energy, persistent current approaches the behavior of free electrons regardless of the disorder, corresponding to the metallic feature. Away from the resonant state, the current is dramatically diminished, indicating an insulative feature. We suggest our results have potential application in designing quantum switch devices.