Magnetic field dependence of the superconducting gap node topology in non-centrosymmetric CePt$_3$Si

Abstract

The non-centrosymmetric superconductor CePt$_3$Si is believed to have a line node in the energy gap arising from coexistence of s-wave and p-wave pairing. We show that a weak c-axis magnetic field will remove this line node, since it has no topological stability against time-reversal symmetry breaking perturbations. Conversely a field in the $a-b$ plane is shown to remove the line node on some regions of the Fermi surface, while bifurcating the line node in other directions, resulting in two 'boomerang'-like shapes. These line node topological changes are predicted to be observable experimentally in the low temperature heat capacity.