Volovik effect ($\gamma (B)\propto \sqrt{B}$)

Vortex superflow Doppler-shifts low-energy quasiparticles in a nodal superconductor. For a circular cell of radius $R\propto B^{-1/2}$ and flow magnitude proportional to $1/r$, its spatially averaged magnitude is proportional to $1/R$. A linearly vanishing nodal density of states then acquires a zero-energy contribution proportional to $\sqrt{B}$, producing a low-temperature linear heat-capacity coefficient with that scaling. This is a clean semiclassical mixed-state estimate; the vector flow average can be zero, and disorder, screening, core states and other field effects change its range of validity.