Optically induced coherent intraband dynamics in disordered semiconductors

Abstract

On the basis of a tight-binding model for a strongly disordered semiconductor with correlated conduction-and valence band disorder a new coherent dynamical intra-band effect is analyzed. For systems that are excited by two, specially designed ultrashort light-pulse sequences delayed by τ relatively to each other echo-like phenomena are predicted to occur. In addition to the inter-band photon echo which shows up at exactly t = 2τ relative to the first pulse, the system responds with two spontaneous intra-band 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.

Localization on a two-channel model with cross-correlated disorder

“…In contrast, antisymmetric crosscorrelations ( −1 j = − +1 j ) substantially inhibit the Anderson localization, especially in the regime of strongly coupled chains. It is interesting to stress that the role of symmetric and antisymmetric correlations has been previously investigated in the context of Coulomb-correlated electron-hole pairs in disordered semiconductors [27,28]. It has been shown that the delocalization action of the Coulomb potential is also stronger for antisymmetrically correlated electron-hole site energies, in close correspondence with our present results.…”