Dynamics of transient disordered vortex states in Bi₂Sr₂CaCu₂O_8+δ

The dynamics of transient disordered vortex states in Bi₂Sr₂CaCu₂O_8+δ was magneto-optically traced in three experiments: (i) during continuous injection of transient vortex states while ramping up the external magnetic field, (ii) during annealing of injected transient states while keeping the external field constant, and (iii) during annealing of transient “supercooled” disordered states while ramping down the external field. The results reveal frontlike propagation [experiment (i)] or retreat [experiments (ii) and (iii)] of the transient vortex states, at a rate governed by the rate of change of the external field, the annealing time τ of the transient states and the creep rate. The experimental results are theoretically analyzed in terms of competition between generation and annealing of transient disordered vortex states. Extraction of the annealing time τ from the above three experiments yields the same results for τ as a function of the induction B and temperature T. Knowledge of τ(B, T) allows for correct determination of the thermodynamic order-disorder vortex phase-transition line.