Nodal quasiparticle power laws

Near clean two-dimensional d-wave nodes, linearized quasiparticle energies form anisotropic cones. Their low-energy density of states is proportional to $|E|$, so electronic heat capacity scales as $T^2$ rather than the activated low-temperature form of a full gap. The clean in-plane penetration-depth increment is linear in T. Disorder, dimensional effects, vortex fields and gap changes can alter these laws, so the assumptions should accompany any proposed diagnostic.