Bound states in time-dependent quantum transport: Oscillations and memory effects in current and density

The presence of bound states in a nanoscale electronic system attached to two biased, macroscopic electrodes is shown to give rise to persistent, non-decaying, localized current oscillations which can be much larger than the steady part of the current. The amplitude of these current oscillations and of the corresponding density oscillations depends on the entire history of the applied potential. The bound-state contribution to the time-averaged density turns out to be history-dependent as well and leads to a natural definition of the bound-state occupations out of equilibrium.