Optically induced coherent intraband dynamics in disordered semiconductors

On the basis of a tight-binding model for a strongly disordered semiconductor with correlated conduction- and valence-band disorder a coherent dynamical intraband effect is analyzed. For systems that are excited by two specially designed ultrashort light-pulse sequences delayed by τ relatively to each other echolike phenomena are predicted to occur. In addition to the interband photon echo which shows up at exactly t=2τ relative to the first pulse, the system responds with two spontaneous intraband current pulses preceding and following the appearance of the photon echo. The temporal splitting depends on the electron-hole mass ratio. Calculating the population relaxation rate due to Coulomb scattering, it is concluded that the predicted new dynamical effect should be experimentally observable in an interacting and strongly disordered system, such as the Quantum Coulomb Glass.