DISSIPATIVE CHAOS IN SEMICONDUCTOR SUPERLATTICES

We consider the motion of ballistic electrons in a miniband of a semic onductor superlattice (SSL) under the influence of an external, time-p eriodic electric field. We use a semiclassical, balance-equation appro ach, which incorporates elastic and inelastic scattering (as dissipati on) and the self-consistent field generated by the electron motion. Th e coupling of electrons in the miniband to the self-consistent held pr oduces a cooperative nonlinear oscillatory mode which, when interactin g with the oscillatory external field and the intrinsic Bloch-type osc illatory mode, can lead to complicated dynamics, including dissipative chaos. For a range of values of the dissipation parameters we determi ne the regions in the amplitude-frequency plane of the external field in which chaos can occur. Our results suggest that for terahertz exter nal fields of the amplitudes achieved by present-day free-electron las ers, chaos may be observable in SSL's. We clarify the nature of this i nteresting nonlinear dynamics in the superlattice-external-field syste m by exploring analogies to the Dicke model of an ensemble of two-leve l atoms coupled with a resonant cavity field, and to Josephson junctio ns.