  We study the dynamics of the electron current in nanodevices where there are
time-varying components and interactions. These devices are a nanojunction
attached to heat baths and with dynamical electron-phonon interactions and a
nanojunction with photon beams incident and reflected at the channel. We use
the two-time nonequilibrium Green's functions technique to calculate the
time-dependent electron current flowing across the devices. We find that
whenever a sudden change occurs in the device, the current takes time to react
to the abrupt change, overshoots, oscillates, and eventually settles down to a
steady value. With dynamical electron-phonon interactions, the interaction
gives rise to a net resistance that reduces the flow of current across the
device when a source-drain bias potential is attached. In the presence of
dynamical electron-photon interactions, the photons drive the electrons to
flow. The direction of flow, however, depends on the frequencies of the
incident photons. Furthermore, the direction of electron flow in one lead is
exactly opposite to the direction of flow in the other lead thereby resulting
in no net change in current flowing across the device.
