COULOMB-RENORMALIZED INTRABAND DYNAMICS PROBED BY THZ EMISSION

THz emission from a narrow-miniband superlattice excited at its lower band edge reveals a hyperbolic bias dependence of the emission frequen cy. This reflects the emission from Coulomb-reaormalized states, namel y the anticrossing between the miniband exciton and the hh_(2) and hh_ (1) Wannier-Stark,ladder states visible in the interband absorption sp ectra. An analysis of the intraband and interband dephasing times, res pectively, reveals that the intraband dynamics remains to be Coulomb-r enormalized even after the dephasing of the interband coherence. This demonstrates that THz emission is dominated by long-lived excitionic c ontributions, in contrast to predictions at a Hartree-Fock level. The dynamics controlled truncation (DCT) approach taking into account the dynamics of the four-point correlation for the intraband current densi ty is able to account for this experimental observation.