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

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The origin of uniaxial and hydrostatic pressure effects on Tc 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, ∂ Tc/∂ Pₐ>0, ∂ Tc/∂ Pc<0, with a hydrostatic response ∂ Tc/∂ P>0 for both La214 and Hg1201 cuprates, in qualitative agreement with experiments. Physically, this is shown to come from a unified picture in which higher Tc is achieved with an "orbital distillation", namely, the less the dₓ₂₋y₂ main band is hybridized with the dz₂ and 4s orbitals higher the Tc. Some implications for obtaining higher Tc materials are discussed.