Magnetic-field dependence of the low-temperature specific heat

Recently, possible evidence from the low-temperature specific heat (LTSH) for the lines of nodes in the superconducting order parameter of cuprate superconductors has attracted much attention and is still debated. To clarify this issue and to cover the studies in different carrier doping regimes, we have measured LTSH of (Formula presented) ((Formula presented) 0.16, and 0.22) both in zero and applied magnetic fields. In all doping regimes, it is found that the increase in the linear-T coefficient γ is proportional to (Formula presented) consistent with d-wave superconductivity. The data shows clear evidence for an (Formula presented) term at zero magnetic field in LTSH of (Formula presented) Furthermore, our results are compared with the recently proposed scaling theory.