Berlin 2008 – scientific programme

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DY: Fachverband Dynamik und Statistische Physik

DY 17: Poster I

DY 17.22: Poster

Tuesday, February 26, 2008, 16:00–18:00, Poster C

Effect of noise and delay near a global bifurcation in superlattices — •Johanne Hizanidis and Eckehard Schöll — Institut f. Theor. Physik, Sekr. EW 7-1, Technische Universität Berlin, Hardenbergstr. 36, 10623 Berlin, Germany

We investigate the effect of time-delayed feedback control and Gaussian white noise on a semiconductor superlattice. Superlattices are spatially extended systems with complex dynamics of interacting fronts. The system is prepared in a regime where the deterministic dynamics is characterized by a global bifurcation, namely a saddle-node bifurcation on a limit cycle (SNIPER). Physically such a bifurcation governs the transition from stationary to traveling field domains through the device. The SNIPER is associated with excitability and therefore the phenomenon of coherence resonance can be verified in the addition of noise below the bifurcation: Noise forces stationary fronts to move and at an optimal noise intensity the regularity of the front motion exhibits a maximum. The possibility to control the noise-induced motion through time-delayed feedback comes into question next. But first the effect of delay without noise is considered. We are able to show that delay induces a homoclinic bifurcation. This result is in agreement to a generic model for the SNIPER with delay. Finally, with both noise and delay, we show how one is able to manipulate characteristic time scales of the system and enhance or deteriorate the coherene resonance effect.