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

摘要

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 ?T_c/?P_a > 0, ?T_c/?P_c < 0, with a hydrostatic response ?T_c/?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 T_c is achieved with an "orbital distillation," namely, the less the d_(x~2-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.