  A net circulating current may appear within a quantum ring under finite bias.
We study the characteristic features of the circular current in the presence of
Rashba spin-orbit interaction (RSOI). Both charge and spin currents appear
within the ring. Whereas when the ring is symmetrically connected to the
external leads, we can get a pure charge current at non-zero Fermi-energy. On
the other hand, for asymmetric ring-to-leads configuration, at zero
Fermi-energy, the spin current vanishes but a pure charge current flows within
the ring. Tuning RSOI, we demonstrate a way to control the pure spin current
externally. This new perspective of the generation of the pure spin circular
current can open a new basis for the highly efficient, low energy cost
spintronic devices.

Mesoscale and Nanoscale Physics