Modulation of persistent current in graphene quantum rings

We investigate the effect of long-range impurity potentials on the persistent current of graphene quantum rings in the presence of an uniform perpendicular magnetic field. The impurity potentials are modeled as finite regions of the ring with a definite length. We show that, due to the relativistic and massless character of the charge carriers in graphene, the effect of such non-uniform potentials on the energy spectrum and on the persistent current of the rings can be reliably modeled by assuming a non-perturbed ring and including an additional phase due to the interaction of the charge carriers with the potential. In addition, the results show the presence of localized states in the impurity regions. Moreover, we show that for the case of a potential created by a p-n-p junction, the persistent current can be modulated by controlling the voltage at the junction.

Oscillatory persistent currents in quantum rings

The density functional theory is used to study persistent currents in two-dimensional quantum rings containing several electrons. We find a series of magic numbers for the total angular momentum of electrons in the strong magnetic field and show that changes in the angular momentum of electrons lead to persistent current oscillations. We suggest an empirical expression for the period of persistent current in quantum rings and examine the effect of Coulomb interaction on the properties of persistent currents.