Figure 1: Schematic representation of the variation of the energy gap (order parameter) plotted as function of the local angle circling the hole ($\alpha$) and electron ($\beta$) Fermi surfaces of the material. Dashed line represents $\mathrm{\Delta }=0$. (a) Isotropic $s\pm$ state. (b) Anisotropic $s\pm$ state with nodes on $\beta$ pockets. (c) Same as (b) but for a state with marginal (“kissing”) nodes. (d) Same as (b) but for deep gap minima.