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

TL;DR

This paper investigates how magnetic fields affect the topology of the superconducting gap nodes in CePt$_3$Si, revealing that magnetic orientation can remove or bifurcate line nodes, which can be experimentally observed through heat capacity measurements.

Contribution

It demonstrates the magnetic field dependence of the superconducting gap node topology in CePt$_3$Si, showing how different field directions alter the line node structure.

Findings

Weak c-axis magnetic field removes the line node.

In-plane magnetic field bifurcates the line node.

Predicted observable changes in heat capacity at low temperatures.

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.