Long-Range Translational Order in Two-Dimensional Chiral Active Crystals

In this chapter, we study two-dimensional athermal chiral active particles at high densities. The particles in this system undergo circular motion. We show that the system crystallizes at high densities even in two dimensions, accompanied by true long-range translational order. This behavior originates from the anomalous suppression of displacement fluctuations associated with hyperuniformity. These findings are quantitatively explained using an active elastic theory.