Stability of nodal quasi-particles in superconductors with coexisting orders

TL;DR

This paper derives a condition for the stability of zero-energy nodal points in superconductors with coexisting orders, highlighting the role of symmetry and discussing implications for cuprate superconductors.

Contribution

It establishes a symmetry-based criterion for the perturbative stability of nodal points in superconductors with coexisting commensurate orders.

Findings

Nodes are stable if the Hamiltonian is invariant under time reversal followed by a lattice translation.

The principle is demonstrated with specific examples.

Implications for cuprate superconductors are discussed.

Abstract

We establish a condition for the perturbative stability of zero energy nodal points in the quasi-particle spectrum of superconductors in the presence of coexisting \textit{commensurate} orders. The nodes are found to be stable if the Hamiltonian is invariant under time reversal followed by a lattice translation. The principle is demonstrated with a few examples. Some experimental implications of various types of assumed order are discussed in the context of the cuprate superconductors.