Impurity scattering effects on the low-temperature specific heat of d-wave superconductors

Recently, impurity scattering effects on quasiparticles in d-wave superconductors have attracted much attention. In particular, the thermodynamic properties in magnetic fields are of interest. We have measured the low-temperature specific heat (Formula presented) of (Formula presented) The impurity scattering effects on (Formula presented) of cuprate superconductors were clearly observed and are compared with the theory of d-wave superconductivity. It is found that impurity scattering leads to the relation (Formula presented) in small magnetic fields. Surprisingly, the scaling of (Formula presented) is broken down by impurity scattering.