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 LaO1-xFxFeAs and other such systems based on FeAs layers, several proposals have been made for the superconducting order parameter Delta(k), on both phenomenological and microscopic grounds. Here we discuss how the symmetry of Delta(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 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.