Anomalous scaling of ΔC versus Tc in the Fe-based superconductors: the -wave pairing state model

Abstract

The strong power law behavior of the specific heat jump versus Tc, first observed by Bud’ko et al (2009 Phys. Rev. B 79 220516), has been confirmed with several families of the Fe-based superconducting compounds with various dopings. We have tested a minimal two band BCS model to understand this anomalous behavior and showed that this non-BCS relation between versus Tc is a generic property of the multiband superconducting state paired by a dominant interband interaction () reflecting the relation near Tc, as in the -wave pairing state. We also found that this versus Tc power law can continuously change from the ideal BNC scaling to a considerable deviation by a moderate variation of the impurity scattering rate (non-pair-breaking). As a result, our model provides a consistent explanation why the electron-doped Fe-based superconductors follow the ideal BNC scaling very well while the hole-doped systems often show varying degree of deviations.