Coulomb blockade in an open small ring with strong backscattering

A comparative study of Coulomb blockade oscillations in a small quantum ring with effective radius 100 nm in ordinary tunnelling and anomalous open regimes is performed. We demonstrate that even though there is no tunnelling barrier between the ring and 2D electron sea in this ring, gigantic Coulomb blockade-like oscillations can be observed. Gate voltage, DC bias and temperature dependences of the ring conductance were experimentally studied at temperatures 0.24-1.4K and magnetic fields up to 1.5T. These studies show the principal differences between Coulomb blockade oscillations in the tunnelling regime and in the open state. The fundamental single-electron period of the oscillations is found to be the same in both regimes. The role of backscattering processes is concluded to be the reason for the existence of strong Coulomb blockade effects in the open state of the ring. (C) 2007 Elsevier B.V. All rights reserved.