Terahertz response of optically excited semiconductors

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.