The heat capacity of superconducting Na xCoO 2· yH 2O was measured and the data are discussed based on two different models: The BCS theory and a model including the effects of line nodes in the superconducting gap function. The electronic heat capacity is separated from the lattice contribution in a thermodynamically consistent way maintaining the entropy balance of superconducting and normal states at the critical temperature. It is shown that for a fully gapped superconductor the data can only be explained by a reduced (≈50%) superconducting volume fraction. The data are compatible with 100% superconductivity in the case where line nodes are present in the superconducting gap function.
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics
- Energy Engineering and Power Technology
- Electrical and Electronic Engineering