Multiorbital analysis of the effects of uniaxial and hydrostatic pressure on T c in the single-layered cuprate superconductors

The origin of uniaxial and hydrostatic pressure effects on ${T}_{c}$ in the single-layered cuprate superconductors is theoretically explored. A two-orbital model, derived from first principles and analyzed with the fluctuation exchange approximation gives axial-dependent pressure coefficients $\ensuremath{\partial}{T}_{c}/\ensuremath{\partial}{P}_{a}g0$, $\ensuremath{\partial}{T}_{c}/\ensuremath{\partial}{P}_{c}l0$, with a hydrostatic response $\ensuremath{\partial}{T}_{c}/\ensuremath{\partial}Pg0$ for both La214 and Hg1201 cuprates, in qualitative agreement with experiments. Physically, this is shown to come from a unified picture in which higher ${T}_{c}$ is achieved with an ``orbital distillation,'' namely, the less the ${d}_{{x}^{2}\ensuremath{-}{y}^{2}}$ main band is hybridized with the ${d}_{{z}^{2}}$ and $4s$ orbitals the higher the ${T}_{c}$. Some implications for obtaining higher ${T}_{c}$ materials are discussed.