Figure 1
Illustration: Alan Stonebraker

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