Regensburg 2013 – scientific programme

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DY: Fachverband Dynamik und Statistische Physik

DY 33: Poster II

DY 33.31: Poster

Thursday, March 14, 2013, 17:00–19:00, Poster C

Orientational pattern selection by traveling modulations — •Lisa Rapp, Vanessa Weith, Alexei Krekhov, and Walter Zimmermann — Universität Bayreuth, Theoretische Physik, 95440 Bayreuth, Germany

The process of pattern formation in two-dimensional isotropic systems has been investigated intensively during the last decades. Challenging tasks in these systems are for instance the suppression defects in stripe patterns and the control of the overall orientation of the evolving structures.

We suggest an effective approach to control the pattern morphology by applying a traveling long-wave periodic modulation of the control parameter of the pattern forming system. The model systems we investigate include the Swift-Hohenberg equation (describing e.g. Rayleigh-Bénard convection) and the evolution equation for microphase separation in symmetric diblock copolymers. Studying the onset of the stripe phase we find, that depending on the traveling velocity v different orientations of the stripes with respect to the modulation may be favoured near threshold. In the case of a stationary modulation the wave vector of the stripes is preferentially perpendicular to the wave vector of the forcing. This also holds for velocities smaller than a velocity v₁. For velocities larger than a velocity v₂ a parallel orientation of the wave vectors has the lowest threshold. In the intermediate range v₁ < v < v₂ both wave vectors adjust themselves at an angle between 0 and π/2.

This velocity-dependent (re)orientation effect is confirmed by numerical simulations as well as the fact that the stripe patterns exhibit much less defects than in the unmodulated case.