Dumbbell diffusion in a spatially periodic potential

Abstract

We present a numerical investigation of the Brownian motion and diffusion of a dumbbell in a two-dimensional periodic potential. Its dynamics is described by a Langevin model including the hydrodynamic interaction. With increasing values of the amplitude of the potential we find along the modulated spatial directions a reduction of the diffusion constant and of the impact of the hydrodynamic interaction. For modulation amplitudes of the potential in the range of the thermal energy the dumbbell diffusion exhibits a pronounced local maximum at a wavelength of about 3/2 of the dumbbell extension. This is especially emphasized for stiff springs connecting the two beads. Introduction.-Investigations on the diffusion of different colloidal particles in a homogeneous solvent have a long history [1,2], while studies on the diffusion of small spheres, dimers and polymers in different potentials attract considerable interest only for a short time [3,4,5,6,7,8,9]. Laser-tweezer arrays are a new powerful tool for generating the desired spatially periodic, correlated or unstructured potentials in order to study the effects of inhomogeneous potential landscapes on the motion of colloidal particles [3,4,5,10]. Furthermore recent studies of dumbbells and polymers in random potentials are exciting issues in statistical physics [11,12].

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