Extreme Spontaneous Deformations of Active Crystals

Abstract

We demonstrate that two-dimensional crystals made of active particles can experience extremely large spontaneous deformations without melting. Using particles mostly interacting via pairwise repulsive forces, we show that such active crystals maintain long-range bond order and algebraically-decaying positional order, but with an exponent $\eta$ not limited by the $\frac{1}{3}$ bound given by the (equilibrium) KTHNY theory. We rationalize our findings using linear elastic theory and show the existence of two well-defined effective temperatures quantifying respectively large-scale deformations and bond-order fluctuations. The root of these phenomena lies in the sole time-persistence of the intrinsic axes of particles, and they should thus be observed in many different situations.

6 pages, 4 figures

References in corpus (4)

• Motility-Induced Phase Separation
• Purely hydrodynamic ordering of rotating disks at a finite Reynolds number
• Universal hydrodynamic mechanisms for crystallization in active colloidal suspensions
• Defect-Mediated Phase Transitions in Active Soft Matter