Specific Heat and Superfluid Density for Possible Two Different Superconducting States in NaxCoO2.yH2O

TL;DR

This paper microscopically calculates specific heat and superfluid density in NaxCoO2.yH2O, reconciling conflicting experimental data by proposing two possible pairing states: extended s-wave and p-wave.

Contribution

It introduces a microscopic model that explains diverse thermodynamic measurements by suggesting two distinct superconducting pairing states in the material.

Findings

Reproduces specific heat data for both extended s-wave and p-wave states.

Reproduces superfluid density data corresponding to each pairing state.

Supports the existence of two different superconducting pairing states in NaxCoO2.yH2O.

Abstract

Several thermodynamic measurements for the cobaltate superconductor, NaxCoO2.yH2O, have so far provided results inconsistent with each other. In order to solve the discrepancies, we microscopically calculate the temperature dependences of specific heat and superfluid density for this superconductor. We show that two distinct specific-heat data from Oeschler et al. and Jin et al. are reproduced, respectively, for the extended s-wave state and the p-wave state. Two different superfluid-density data are also reproduced for each case. These support our recent proposal of possible two different pairing states in this material. In addition, we discuss the experimentally proposed large residual Sommerfeld coefficient and extremely huge effective carrier mass.