A unified model for the uniaxial and hydrostatic pressure dependence of Tc in YBa2Cu3Ox (x ≈ 6.95–7.0)

Abstract Though the uniaxial and hydrostatic pressure dependence of T c yield important insight into the superconductivity of YBa 2 Cu 3 O x ( x  ≈ 6.95–7.0), the understanding of the origin of the pressure effect on this system remains lack of a unified model explanation in a quantitative manner. In order to develop a unified model, we performed first-principles calculations for YBa 2 Cu 3 O 7 under pressure to distinguish the core factors including holes concentration and tetragonality and further combined the two factors with the charge-transfer model to determine the T c . The role of tetragonality was identified in determining the uniaxial pressure effect significantly but not as prominent as holes concentration in producing the superconductivity of YBa 2 Cu 3 O x ( x  ≈ 6.95–7.0). The results under pressure from the unified model based on the newly defined tetragonality and holes concentration are in good accordance with that from experiments. With this unified model, we predicted that the better superconductivity in YBa 2 Cu 3 O x ( x  ≈ 6.95–7.0) may appear through 0.025 compression along b axis or 0.025 stretching along a axis.