Fig. 4. Scaling of the zero-temperature superfluid density and the T-linear resistivity coefficient for unconventional superconductors.

(A) Scaling of ρ_s0 with $\tilde{A}$₁^□ for different superconducting systems, where ρ_s0 and $\tilde{A}$₁^□ are normalized by their respective maximum values in the literature. Here, a constant has been subtracted from A₁^□, namely, $\tilde{A}$₁^□ = A₁^□ − A₀, where A₀ represents the nonzero extrapolation of A₁ to T_c = 0 K (5). Data for Ba(Fe_1−xCo_x)₂As₂ (BFCA) are extracted from (3, 34). Data for Tl₂Ba₂CuO_6+δ (Tl2201) are obtained from (22) and references therein. Data for heavily overdoped La_2−xSr_xCuO₄ (LSCO; $T_{\mathrm{c}}\le 12\mathrm{K}$ ) are extracted from (5, 20). The error bars are reproduced from published data. The red shading is a guide to the eye. (B) ρ_s0 versus A₁ relation calculated on the basis of the 2D-YSYK model (Materials and Methods and Supplementary Text 8), where $\hslash$ is the reduced Planck’s constant and t is the fermion hopping.