A critical assessment of the pairing symmetry in NaxCoO2.yH2O

TL;DR

This paper critically evaluates possible pairing symmetries in NaxCoO2.yH2O, narrowing down to two f-wave states, and proposes experiments to distinguish between them, considering odd-frequency pairing and experimental evidence.

Contribution

It systematically eliminates most pairing states, identifying two viable f-wave states, and suggests experimental tests to determine the actual pairing symmetry in the compound.

Findings

Narrowed down pairing states to two f-wave types

Discussed experimental signatures to distinguish pairing symmetries

Explored the role of odd-frequency pairing in the material

Abstract

We examine each of the symmetry-allowed pairing states of NaxCoO2.yH2O and compare their properties to what is experimentally and theoretically established about the compound. In this way, we can eliminate the vast majority of states that are technically allowed and narrow the field to two, both of f-wave type states. We discuss the expected features of these states and suggest experiments that can distinguish between them. We also discuss odd-frequency gap pairing and how it relates to available experimental evidence.