Energy Dissipation in Cyclic Strain of Amorphous Solids

The study of the response of amorphous materials to oscillatory strain is traditionally performed with many repeated cycles. We argue that it pays to consider carefully just one cycle (and may be a second), to reveal the rich physics that characterizes cyclic strain. The response can be conservative or dissipative, with a sharp transition between these options as a function of preparation parameters, accompanied by symmetry breaking and the onset of screening. We choose an example for which the mesoscopic theory can be solved exactly, and the microscopic physics can be revealed by numerical simulations. The mechanism of energy dissipation (when it exists) is explored in detail, shedding light on the reason why repeated cycles exhibit ever decreasing dissipation per cycle, which is often consistent with a universal law.