Critical behavior associated with transient dynamics near the depinning transition

We study the general phenomenon of plastic depinning using a vortex system confined in a Corbino-disc superconductor. For an ordered initial vortex configuration, the vortices driven by a suddenly applied dc current (force) are gradually pinned to random pinning centers, indicating dynamic disordering. This is detected from the decaying of voltage V(t) (mean velocity) toward a steady-state value V-infinity. On the other hand, when the initial configuration is disordered, a gradual increase of V(t) toward V-infinity is observed, reflecting dynamic ordering. In both cases, relaxation times to reach the steady state exhibit a power-law divergence at the depinning current. Our results clearly show that the transient response depends on the initial vortex configurations: however, the transient time as well as the final mean vortex velocity only depends on the applied current, and the critical behaviors of the depinning transition are identical. To the best of our knowledge, this work is the first to demonstrate this fact predicted by numerical simulations and other more indirect experiments (e.g. Perez Daroca et al 2011 Phys. Rev. B 84 012508).