  Real-time nonequilibrium quantum dynamics of electrons in double-dot
Aharonov-Bohm (AB) interferometers is studied using an exact solution of the
master equation. The building of the coherence between the two electronic paths
shows up via the time-dependent amplitude of the AB oscillations in the
transient transport current, and can be enhanced by varying the applied bias on
the leads, the on-site energy difference between the dots and the asymmetry of
the coupling of the dots to the leads. The transient oscillations of the
transport current do not obey phase rigidity. The circulating current has an
anti-symmetric AB oscillation in the flux. The non-degeneracy of the on-site
energies and the finite bias cause the occupation in each dot to have an
arbitrary flux dependence as the coupling asymmetry is varied.
