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DY: Dynamik und Statistische Physik

DY 46: Poster

DY 46.18: Poster

Donnerstag, 11. März 2004, 16:00–18:00, Poster D

Stochastic resonance in colloidal systems — •Dusan Babic^1,2, Carmen Schmitt¹, Igor Poberaj², and Clemens Bechinger¹ — ¹2. Physikalisches Institut, Universität Stuttgart, Pfaffenwaldring 57, 70550 Stuttgart — ²Faculty of mathematics and physics, University of Ljubljana, Jadranska 19, 1000 Ljubljana, Slovenia

The concept of stochastic resonance (SR) has been used to describe very different effects such as the periodic occurence of the ice ages, the feeding behavior of paddlefish or human balance control and visual perception. The essential feature of SR is that in nonlinear systems noise can improve the detection of weak periodic signals.

Although characteristic features of SR have been observed in several experiments, there are only few examples where the effect is studied on a microscopic level. Colloids - mesoscopic particles which are coupled to a thermal bath and therefore undergo Brownian motion - are a system with intrinsic noise where the time and length scales are conveniently accessible with experiments. As such they provide an excellent model system for fundamental experiments of SR. We investigate the dynamics of a colloidal particle in a double-well potential, the latter being created by optical tweezers. For asymmetric modulation of the potential (corresponding to a tilt) we observe the typical signatures of SR in the residence time distribution and in the power spectrum. In contrast, if we only modulate the height of the potential barrier we do not observe any synchronization between the modulation and the particle dynamics.