  The induced terahertz response of semiconductor systems is investigated with
a microscopic theory. In agreement with recent terahertz experiments, the
developed theory fully explains the ultrafast build up of the plasmon resonance
and the slow formation of incoherent excitonic populations. For incoherent
conditions, it is shown that a terahertz field exclusively probes the
correlated electron-hole pairs via a symmetry breaking between many-body
correlations with even and odd functional form.
