Dependence of superconducting transition temperature on oxygen content and number of CuO 2 layers in mercury-based cuprates

Abstract

The oxygen content effects on the superconducting transition temperature in the HgBa 2Ca n−1Cu nO 2n+2+δ(n=1–5) have been analyzed systematically in terms of the bond valence sums. The parabolic correlation between the T c and Cu valence is observed for the single, double and triple CuO 2 layer materials. Inhomogeneous charge distribution in the two type of CuO 2 planes is found when n⩾3. The nonmonotonic dependence of the maximum T c on n is investigated on the basis of both the total mobile hole concentration in the octahedral or pyramidal CuO 2 planes at the optimal level and the generalized Lawrence-Doniach theory.