Low temperature specific heat studies on the pairing states of high-Tc superconductors: a brief review Original Research Article

Low temperature specific heat (LTSH) data on a variety of high-Tc superconductors, such as YBa2Cu3O7, La1−xSrxCuO4, Bi2Sr2CaCu2O8, and Ba0.6K0.4BiO3 are reviewed. The agreement between the experimental data and theoretical predictions, such as T2-dependence of specific heat at zero magnetic field and H1/2-dependence of electronic specific heat is widely discussed within the scenario of d-wave superconductivity. Impurity scattering effects and scaling model on d-wave superconductivity are verified using Zn- and Ni-doped La1−xSrxCuO4. The low energy quasiparticle density of states N(E)=N(0)+E1/2 are deduced from dirty d-wave superconductors. Absence of paramagnetic contribution to LTSH is found both in superconducting and non-superconducting underdoped samples suggesting that a mechanism beyond Kondo screening model maybe required to explain its magnetic property.