Effects of the velocity on the reversible-irreversible transition in a periodically sheared vortex system

Abstract

Abstract A reversible-irreversible transition (RIT) is studied using a periodically-driven vortex system in an amorphous film with random pinning that causes local shear, as a function of shear amplitude d. The relaxation time to reach the steady state exhibits a power-law divergence at a threshold value dc with critical exponents in agreement with the values predicted for an absorbing phase transition in the two-dimensional (2D) directed-percolation (DP) universality class. In our previous work, the experiment was conducted at relatively high frequency f, giving rise to a large mean vortex velocity v. Here we use lower f to study the effects of reduced v and increased dynamic pinning on the RIT. The results show that the critical behavior of RIT stays essentially unchanged, while we find a trend for dc to increase with decreasing v. We will propose a possible model to qualitatively explain this unexpected result.