This preset shows again the response to an electric field, except that now the inelastic scattering has been replaced by elastic scattering. Run this for about 20 ps. Initially the replacement makes little difference, but gradually you see more and more electrons excited above the Fermi energy. This excess energy is plotted (in units of the Fermi energy per electron) by the red curve in the graph. We speak of heating of the electron gas. For a while at least, the current (proportional to the <k>) is not influenced by the heating.
Now change the tau-i slider to 5 ps and run again (without initializing). Even though the inelastic time is five times longer than the elastic, the inelastic time is able to maintain the system in a stable steady state. The magnitude of the current, however, continues to be determined predominantly by the elastic time.