Analysis of specific heat in YBa2Cu3O7-δ ceramic superconductors

The specific heat anomalies of YBa2Cu3O7-δ superconductors have been theoretically analyzed between 5 and 120 K. The lattice contribution to the specific heat is well estimated from the Debye and Einstein model. We have used the characteristic phonon frequencies deduced from the layered electron gas approach of quasi-two dimensional conducting CuO2 layers. The deduced results on the behaviour of specific heat (C) with temperature (T) follows the same trend as revealed from experiments. The estimated lattice contribution, when subtracted from the experimental data results in a finite value of electronic specific heat coefficient (γ) in the superconducting state. Furthermore, ΔC/T shows a definite break in the vicinity of Tc when the graph is extrapolated in the range of 70 K ≤ T ≤ 110 K. We have also estimated the density of states at the Fermi level which is consistent with earlier reports. The implications of the above analysis are discussed. (orig.)