  Recent numerical calculation of the intrinsic thermal Hall conductivity of
nodal d-wave superconductors in the mixed state revealed a rapid increase of
this quantity above an onset temperature. Interestingly, this defines a
measurable energy scale in an otherwise gapless state. Using the mathematics of
magnetic coherent states, in this paper such energy scale is related to a
dynamical process associated with the Andreev scattering of an electron
wavepacket moving along the constant energy contours in the momentum space.
This energy scale is then used to obtain an improved scaling collapse of
numerically calculated thermal Hall conductivity in a tight-binding model as a
function of temperature, magnetic field and the d-wave pairing amplitude at
various band fillings. The results indicate that the mentioned onset
temperature is associated with the ability of the quasiparticle wavepacket to
complete its semiclassical orbit before it is appreciably scattered by the
superconducting condensate.
