Memory of elastic collisions drives high minority spin and oscillatory entropy in underdamped chiral spinners

Inertial underdamped collisions preserve the memory of physical parameters that existed before the collision, leading to phenomena usually unseen in overdamped systems. Here we probe the less studied inertial chiral matter with spinners on an air table. We show the emergence of high levels of spin for a minority of (+) handed spinners in the presence of a majority of (−) handed spinners (and vice versa). This deep violation of equipartition occurs due to the inertial (memory preserving) nature of elastic collisions between underdamped translating and rotating objects. Underdamped spinners of the same spin sign annihilate their spins when they elastically collide, transferring their spin angular momentum into orbital angular momentum, while oppositely handed spinners tend to preserve their individual spin levels, leading to the pumping of minority spinners to high spin levels. Entropy production and the flow of entropy in this underdamped system are also counter-intuitive, showing dramatic oscillations in time.

Shengkai Li, Trung V. Phan, Gao Wang, Ramzi Khuri, Jared W. Wilson, Robert H. Austin, Liyu Liu