Conventional mechanisms for "exotic" superconductivity

TL;DR

This paper explores how conventional BCS mechanisms in materials with specific symmetries can lead to complex, time-reversal symmetry-breaking superconducting states with multidimensional order parameters, suggesting potential candidate materials.

Contribution

It demonstrates that symmetry constraints in certain crystal structures can produce exotic superconducting states with broken time-reversal symmetry.

Findings

Symmetry of Fermi surface pockets influences pairing symmetry.

Broken time-reversal symmetry in the proposed states.

Identification strategies for detecting such exotic phases.

Abstract

We consider the pairing state due to the usual BCS mechanism in substances of cubic and hexagonal symmetry where the Fermi surface forms pockets around several points of high symmetry. We find that the symmetry imposed on the multiple pocket positions could give rise to a multidimensional nontrivial superconducting order parameter. The time reversal symmetry in the pairing state is broken. We suggest several candidate substances where such ordering may appear, and discuss means by which such a phase may be identified.