The pressure effects on the superconducting transition temperature (${\mathit{dT}}_{\mathit{c}}$/dP) have been systematically measured for a series of (${\mathrm{Yb}}_{1\mathrm{-}\mathit{x}}$${\mathrm{Pr}}_{\mathit{x}}$)${\mathrm{Ba}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_{7\mathrm{-}\mathrm{\delta }}$ with x ranging from 0 to 0.3. It has been found that ${\mathit{dT}}_{\mathit{c}}$/dP<0 for x=0, 0.2, and 0.3, and ${\mathit{dT}}_{\mathit{c}}$/dP≳0 for x=0.05, 0.075, 0.1, and 0.15. We have unexpectedly observed a pressure-induced increase in the normal state resistivity for x=0.2 and 0.3, suggesting a decrease of the carrier concentration under pressure. Making use of the concept of pressure-induced charge transfer incorporated in the model of hole depletion by Pr doping, we have proposed a phenomenological model, which has successfully explained the x dependences of ${\mathit{dT}}_{\mathit{c}}$/dP and ${\mathit{T}}_{\mathit{c}}$. ©1996 The American Physical Society.

• Received 24 July 1995

DOI:https://doi.org/10.1103/PhysRevB.53.11855