Determining gap nodal structures in Fe-based superconductors: Theory of the angle dependence of the low-temperature specific heat in an applied magnetic field

Since the discovery of high-${T}_{c}$ ${\mathrm{LaO}}_{1\ensuremath{-}x}{\mathrm{F}}_{x}\mathrm{FeAs}$ and other such systems based on $\mathrm{FeAs}$ layers, several proposals have been made for the superconducting order parameter ${\ensuremath{\Delta}}_{\mathbf{k}}$, on both phenomenological and microscopic grounds. Here we discuss how the symmetry of ${\ensuremath{\Delta}}_{\mathbf{k}}$ in the bulk can be determined, assuming that single crystals will soon be available. We suggest that a measurement of the dependence of the low-temperature specific heat on the angle of a magnetic field in the $\mathrm{FeAs}$ plane is the simplest such method, and calculate representative specific heat vs field angle oscillations for the various candidate states, using a phenomenological band structure fitted to the density functional theory Fermi surface.