Composition dependence of the pressure effect onTcin (Yb0.7Ca0.3)(Ba0.8Sr0.2)2Cu3Oz

Abstract

The effect of pressure on the superconducting transition temperature ${\mathit{T}}_{\mathit{c}}$ of (${\mathrm{Yb}}_{0.7}$ ${\mathrm{Ca}}_{0.3}$) (${\mathrm{Ba}}_{0.8}$ ${\mathrm{Sr}}_{0.2}$ ${)}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_{\mathit{z}}$ is investigated for oxygen contents z from z=6.43 to z=6.78. The pressure derivative ${\mathit{dT}}_{\mathit{c}}$/dP shows decreasing positive values for the hole-concentration region where ${\mathit{T}}_{\mathit{c}}$ increases with the hole concentration in the ${\mathrm{CuO}}_2$ plane, ${\mathit{p}}_{\mathrm{pl}}$, and negative constant values for the region where ${\mathit{T}}_{\mathit{c}}$ decreases with ${\mathit{p}}_{\mathrm{pl}}$. The sign and magnitude of ${\mathit{dT}}_{\mathit{c}}$/dP may be determined by not only the carrier type but also pressure-induced enhancements of both the hole concentration and intraplane coupling in the ${\mathrm{CuO}}_2$ plane.