Onset of motion and glassy dynamics of a moving vortex lattice

We study the onset of motion of a vortex lattice in response to a driving current that is turned on suddenly. For sufficiently high currents we find that the average vortex velocity (obtained from the longitudinal voltage drop) grows smoothly with time and obeys a stretched exponential with an exponent β ∼ 0.7. The response is governed by two time scales: a delay time (t ₀) before the appearance of a measurable voltage drop, and a rise time (τ) characterizing the evolution of voltage response. Both time scales increase with decreasing saturation voltage V₀,: τ decreases exponentially, while to as a power law. When the saturation velocity is too low the response slows down significantly and shows a step structure indicating plastic response.