Dynamical phase transition in periodically sheared colloids

This weeks item is Nature Physics paper Random organization in periodically driven systems by Corte, Golub, Chaikin and Pine.

When you consider a dilute suspension of colloidal particles undergoing a periodic driving force – such as shear, at low density and low strain, particles far from their near neighbours will be undergoing periodic motion around the same point. However, if the two

particles are near each other, they are likely to collide during shearing, changing their relative position. These particles can collide until they become sufficiently separated and settle into reversible fluctuations around their positions – hence self-organizing behaviour.

At high values of maximum strain, or at high densities, however, the particles never cease colliding, leading to irreversible dynamics – hence dynamic phase transition above a well-defined strain threshold.