Critical Current Peaks at $3B_{\Phi }$ in Superconductors with Columnar Defects: Recrystallizing the Interstitial Glass

The role of commensurability and the interplay of correlated disorder and interactions on vortex dynamics in the presence of columnar pins is studied via molecular dynamics simulations. Simulations of dynamics reveal substantial caging effects and a nonmonotonic dependence of the critical current with enhancements near integer values of the matching field $B_{\varphi }$ and $3B_{\varphi }$ in agreement with experiments on the cuprates. We find qualitative differences in the phase diagram for small and large values of the matching field.

Figure 1

Resistivity as a function of driving current for different values of the applied magnetic field referenced to the matching field $B_{\Phi }$ for $B_{\Phi }/H_{c2}\times {10}^3=7.32$ (a) and 1.525 (b), respectively. The values of $B/B_{\Phi }$ are indicated as follows: Panel (a): 0.3 (circles), 0.8 (squares), 1 (diamonds), 1.25 (up triangles), 1.48 (left triangles), and 2 (down triangles); and Panel (b): 0.5 (circles), one (squares), 1.5 (diamonds), two (up triangles), three (left triangles), and four (down triangles). Solid lines are guides and become thicker for smaller fields. The insets show the low current resistivities.

Figure 2

Normalized critical currents as a function of $B/B_{\Phi }$ for different densities of columnar defects. The density of defects is given by ${10}^3\times B_{\Phi }/H_{c2}=1.525,1.906,3.05,4.88,$ and $7.32$ for circles, squares, down triangles, diamonds, and up triangles, respectively. Guide lines are thicker for smaller fields.

Figure 3

Conjectured phase diagram for large (a), intermediate (b), and small (c) matching field densities.

Figure 4

Structure factor in the pinned phase at 3 times the matching field $B/B_{\Phi }=3$ for ${10}^3\times B_{\Phi }/H_{c2}=1.525$ (left) and 7.32 (right) panels, respectively. Momentum is measured in units of $1/d$.