Fig. 2

Numerical simulation of the critical current. a The discretized model (or mesh) used in the numerical simulation of the critical current. Since the triplet current is mostly concentrated in the immediate vicinity of the trench, the mesh density (and hence the accuracy) is set to be higher for this region. For the same reason, the regions farthest away from the trench have been removed to reduce the calculation time. b The critical current density divided by a factor \(J_0 = \frac{{N_0eD{\mathrm{\Delta }}}}{{2\xi }}\), where N ₀ is the density of states at the Fermi level, D is the diffusion constant, Δ is the superconducting gap and ξ is the superconducting coherence length. For clarity, currents lower than 10⁻⁷ J ₀ are not shown. c A slice through the centre of the trench, showing how the current passes across the Co barrier in two separate channels, on either side of the vortex core