Topologically stable gapless phases in nonsymmorphic superconductors

TL;DR

This paper demonstrates that nonsymmorphic symmetries can protect topologically stable line nodes in certain superconductors, with implications for understanding their electronic structure and stability.

Contribution

It reveals that nonsymmorphic symmetry combined with topology protects line nodes in odd-parity superconductors, extending the understanding of topological stability beyond traditional group theory.

Findings

Line nodes in UPt3 are topologically protected by nonsymmorphic symmetry.

Spin-orbit coupling is essential for protecting these line nodes.

Generalization to point nodes and other symmetries is proposed.

Abstract

We study topological stability of nodes in nonsymmorphic superconductors (SCs). In particular, we demonstrate that line nodes in nonsymmirphic odd-parity SCs are protected by the interplay between topology and nonsymmorphic symmetry. As an example, it is shown that the $E_{2u}$-superconducting state of UPt$_3$ hosts the topologically stable line node at the Brillouin zone face. Our theory indicates that the existence of spin-orbit coupling is essential for protecting such a line node, complementing the Norman's group theory argument. Developing the topological arguments, we also argue generalization to point nodes and to other symmetry cases beyond the group theory arguments.