Figure 1. Summary of reported J_c and calculated λ.

The temperature dependence of the normalized penetration depth, λ(T)/λ(0) (left-hand scale) calculated from the normalized values of self-field critical current density, J_c(T)/J_c(0) (right-hand scale, as indicated by arrows) for many different type-I and type-II superconductors. Values of λ(T) are calculated using equations (3) and (4). (a,b) s-wave superconductors. (c,d) d-wave superconductors, as also seen by their very different low-T behaviour. The dashed red curves are the fitted s-wave weak-coupling T-dependence of λ(T) and the dashed blue curves are the d-wave counterparts. The dashed black curves are J_c back-calculated from these λ(T) curves using equations (3) and (4). The deduced normalization parameters, T_c, J_c0 and λ₀=λ(0) are listed in Supplementary Table 1. (d) A slightly different analysis for PrOs₄Sb₁₂. Both J_c and λ are calculated from measurements of H_c1 using equation (4), and the calculated J_c is compared with values measured from remnant magnetization (magenta data points). They are in excellent agreement. The two curves (dashed and solid) are obtained by adding two separate d-wave superfluid densities below 0.6 K.