Order-disorder transitions in a sheared many body system

TL;DR

This study investigates how a sheared 2D particle system transitions between ordered and disordered phases, revealing the conditions for lattice formation, shear banding, and reversibility of motion, with implications for understanding suspension behavior.

Contribution

It provides a detailed analysis of phase transitions in a sheared many-body system, highlighting the role of interaction strength and shear rate in the emergence of order and disorder.

Findings

Transitions between ordered and disordered phases depend on interaction strength and shear rate.

Ordered phases evolve into regular lattices on slow time scales.

Disordered states are characterized by shear bands and irreversibility.

Abstract

Motivated by experiments on sheared suspensions that show a transition between ordered and disordered phases, we here study the long-time behavior of a sheared and overdamped 2-d system of particles interacting by repulsive forces. As a function of interaction strength and shear rate we find transitions between phases with vanishing and large single-particle diffusion. In the phases with vanishing single-particle diffusion, the system evolves towards regular lattices, usually on very slow time scales. Different lattices can be approached, depending on interaction strength and forcing amplitude. The disordered state appears in parameter regions where the regular lattices are unstable. Correlation functions between the particles reveal the formation of shear bands. In contrast to single particle densities, the spatially resolved two-particle correlation functions vary with time and allow to determine the phase within a period. As in the case of the suspensions, motion in the state with low diffusivity is essentially reversible, whereas in the state with strong diffusion it is not.