Memory formation in cyclically deformed glasses*

Cyclically shear deformed glasses reach, after a transient regime, periodic orbits involving transitions between basins of energy minima that are visited repeatedly during repeated cycles of deformation, if the amplitude of deformation is not too large. These periodic orbits encode information of their deformation history, and have been shown to retain memory of training at multiple strain amplitudes. Such memory effects, in the presence of plastic rearrangements involved in transitions between basins, is surprising, but appears to be generic. Investigations of the nature of such periodic orbits reveals rich structure, whose analysis permits investigation of the presence or otherwise of features such as return point memory, and suggests protocols by which the encoded information may most efficiently be recovered.