= Volovik effect
{c}
{title2=$\gamma(B)\propto\sqrt B$}
<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.
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