Cyclic Memories in Disordered Matter

The Department of Physics welcomes Dr. Nathan Keim to present a physics virtual colloquia. The talk is geared towards undergraduate students but all are welcome. Dr. Keim is an associate research professor of physics at Penn State University.

Abstract: Cyclic driving happens all around us. Buildings and bridges are repeatedly loaded and unloaded, and many organisms synchronize their functions with day and night. This kind of driving can change a material, and even form memories that can be recalled later. Dr. Keim will present two examples of materials that, when deformed repeatedly in experiments, can “learn” and report the magnitudes of those deformations: a dilute suspension of particles in liquid, and a solid made of jammed particles. These exemplify two different but generic ways that non-equilibrium systems can form memories, with suspensions sharing their behavior with charge-density wave conductors, and amorphous solids approximating the return-point behavior best known in magnetic materials. Exploring memory leads to surprising insights about how each material’s disordered internal state can be prepared, probed, and programmed.