Colóquio Extra 05/12/2023: Extreme Spontaneous Deformations of Active Crystals

I will show that two-dimensional crystals made of active particles can experience extremely large spontaneous deformations without melting. Such active crystals are able to maintain long-range bond order and algebraically decaying positional order, but with an exponent η not limited by the 1/3 bound given by the (equilibrium) KTHNY theory. I will show how these findings can be rationalized within linear elastic theory via the existence of two well-defined effective temperatures quantifying respectively large-scale deformations and bond-order fluctuations. I will finally discuss similar observations made in different situations.