Effect of uniaxial pressure on the superconducting transition in YBa2Cu3O7.

Abstract

The changes in the hole carrier concentrations in ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7}$ are calculated for uniaxial compressions. We find that while a compression along the a axis enhances the hole density, the one along the b axis results in an almost equal decrease. Due to this cancellation, the pressure dependence of ${\mathit{T}}_{\mathit{c}}$ under a hydrostatic pressure is essentially the same as for a uniaxial stress along the c axis. A qualitative discussion is also given of the strikingly different behavior in ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{4}$${\mathrm{O}}_{8}$ which is attributed to the chain-chain interaction in this compound.