Dynamic Phases of Vortices in Superconductors with Periodic Pinning

We present results from extensive simulations of driven vortex lattices interacting with periodic arrays of pinning sites. Changing an applied driving force produces a rich variety of novel dynamical plastic flow phases which are very distinct from those observed in systems with random pinning arrays. Signatures of the transition between these different dynamical phases include sudden jumps in the current-voltage curves as well as marked changes in the vortex trajectories and vortex lattice order. Several dynamical phase diagrams are obtained as a function of commensurability, pinning strength, and spatial order of the pinning sites.

V(I) curve figure

Average vortex velocity versus driving force for a field value slightly above the matching field, with the pinning sites located in a square array. The driving force is increased from 0 to 0.8. Several remarkable jumps in the curve can be clearly seen which correspond to transitions in the dynamical behavior of the driven lattice. To better identify the phases we have numbered them I - IV. The inset shows the hysteresis curve as the driving force is increased to 0.7 and then decreased (phases now shown with unbold Roman numerals) to zero. Some phase boundaries, II-III and III-IV, show hysteresis while others do not.

Trajectories figure

Trajectories of the east-bound flowing vortices, for the voltage-current curve in Fig. 1, for regions: II, interstitial flow (a); III, disordered flow (b); IV, incommensurate 1D flow (c); and V, homogeneous flow (d). The vortices are represented by black dots and pinning sites by open circles. For clarity, only a section of the sample is shown.

Phase diagrams

Dynamic phase diagrams with a square pinning lattice. (a) Pinning force versus driving force. As the driving force is increased, the phase boundaries II-III, III-IV, and IV-V become linear. (b) Ratio of applied field to matching field plotted versus driving force. For ratios greater than 1, regions I through V can be observed, with the disordered region III growing and the ordered-flow regions II and IV reducing in size. (c) Phase diagram for gradually increasing the amount of disorder in the location of the pins. (d) Dynamic phase diagram for matching field versus driving force.

C. Reichhardt, C. J. Olson, and Franco Nori
Physical Review Letters 78, 2648 (1997).

Three Java movies are available:

Return to main page.

Created by: Cynthia Olson
Last modified: 5/14/97