Gap structure probed by field-angle resolved thermal oscillations in CeCoIn5 superconductor

We calculate the angle-resolved oscillations of the specific heat and thermal conductivity in a rotating in-plane magnetic field in the multiband superconductor CeCoIn$_5$ using realistic tight-binding Fermi surfaces. We find that an electron pocket at the $M$ point and a hole pocket at the $\Gamma$ point of the Brillouin zone yield sufficiently large Fermi surface anisotropies to produce fourfold oscillations not only for $d$-wave pairing, but also for $s$-wave pairing in the regime where our approximations are valid for both nodal and isotropic gap, namely near the upper critical field $H_{c2}$ and down to fields of order $H_{c2}/2$. More importantly, in this region we find a sign reversal in the oscillations as a function of temperature and fixed field for all gap symmetries investigated. We compare our results with available data on CeCoIn$_5$ and CeIrIn$_5$ and discuss how Fermi surface anisotropies affect the identification of gap structures and symmetries.