Quantum transport in topological mesoscopic ring structures

We have studied the electronic: transport properties of various topological mesoscopic rings which consist of several variable-size chains joined at their ends to form ideal single-channel leads. An enhancement of the transmission coefficient is obtained when the chain lengths are randomly distributed, due to the suppression of interchain interference, and, in the presence of magnetic flux, periodic magnetoconductance oscillations are also shown. A single impurity changes the magneto-oscillation pattern drastically, while for more impurities placed at random the periodic magnetoconductance oscillations survive. Finally, the introduction of a transverse link between the chains destroys the bridge-cc shape of the transmission versus energy curves obtained in the absence of such a link.