Regensburg 2016 – wissenschaftliches Programm

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DY: Fachverband Dynamik und Statistische Physik

DY 13: Statistical Physics (general)

DY 13.5: Vortrag

Montag, 7. März 2016, 16:00–16:15, H48

From Shapiro-Steps to frozen Kinks — •Thorsten Brazda and Clemens Bechinger — Pfaffenwaldring 57, 70550 Stuttgart, Germany

Although friction is ubiquitous in our everyday lives, a microscopic understanding is still lacking. This is partially due to the small length scales, which are not easily accessible in experiments. To overcome this problem and to observe individual particle motion during sliding, we studied a two-dimensional commensurate colloidal crystal which is driven across a (111) substrate, the latter created by a laser interference pattern [1]. In order to study the effect of substrate lattice vibrations on the sliding motion we have periodically modulated the substrate strength U. For small driving forces F, we observe a cooperative, phase-locked, particle motion which leads to characteristic Shapiro-steps in the mobility-force plane. At higher F, the colloids form an increasing number of local compression zones (kinks) which are still mobile during time-intervals where U is small. On the contrary, for large U, the particle motion is entirely stopped and the kinks are frozen. The formation of kinks leads to an incoherent particle motion which leads to the blurring of Shapiro-steps until they finally disappear at high F.

[1] T. Bohlein J. Mikhael and C. Bechinger, Observation of kinks and antikinks in colloidal monolayers driven across ordered surfaces, Nat. Mater. 11, 126 (2011).