Evidence for two-band superconductivity and non-magnetic pair breaking in Na0.3CoO2 • 1.3H2O;: effects of sample age

The specific heat of Na0.3CoO2 center dot 1.3H(2)O gives evidence of two electron bands with comparable densities of states and different superconducting-state energy gaps. A non-magnetic pair-breaking action, which acts preferentially in the band with the smaller gap, progresses with sample age. The two bands and non-magnetic pair breaking have implications for possible pairing mechanisms; the effects of the pair breaking constitute the sample dependence of the properties of this material. In concert with structural changes reported by others, the specific heat suggests dual roles for O vacancies - tuning the carrier concentration to favor superconductivity, and pair breaking to destroy it. Copyright (c) EPLA, 2008.