Effect of Planar Defects on the Stability of the Bragg Glass Phase of Type-II Superconductors

It is shown that the Bragg glass phase can become unstable with respect to planar crystal defects as twin or grain boundaries. A single defect plane that is oriented parallel to the magnetic field as well as to one of the main axis of the Abrikosov flux line lattice is always relevant, whereas we argue that a plane with higher Miller index is irrelevant, even at large defect potentials. A finite density of parallel defects with random separations can be relevant even for larger Miller indices. Defects that are aligned with the applied field restore locally the flux density oscillations which decay algebraically with distance from the defect. The current-voltage relation is changed to $\ln V(J)\sim -J^{-1}$. The theory exhibits striking similarities to the physics of Luttinger liquids with impurities.

Figure 1

Left: Triangular flux line lattice with vectors of the direct (${\mathbf{a}}_1$ and ${\mathbf{a}}_2$) and the reciprocal lattice (${\mathbf{b}}_1$ and ${\mathbf{b}}_2$) and the orientation of the defect plane. Right: Two lowest order orientations corresponding to $g=\eta /2$ (dotted lines), $3\eta /2$ (dashed lines).