As a layered material, FeSe provides an ideal platform for realizing high-temperature superconductivity and exploring the microscopic pairing mechanisms. Here, we investigate the behavior of superconductivity and orbital-selective pairing of bulk FeSe under different pressuring schemes within first-principles dynamical mean-field theory ($ab$-DMFT). We first confirm that the orthorhombic phase is preferred among the layered structures, and the resultant superconducting transition temperature ($T_{\text{c}}$) is elevated from essentially zero to the experimentally observed order of magnitude only with the inclusion of correlation-enhanced electron-phonon coupling. The vital role of correlation effects is strongly corroborated by our quantitative interpretation of the experimentally observed superconducting dome under hydrostatic pressure. Counter-intuitively, the $T_{\text{c}}$ qualitatively anticorrelates with the correlation strength, as measured by the quasiparticle broadening around the Fermi level. We further investigate the effects of biaxial and uniaxial pressures and predict that uniaxial pressure can induce the emergence of two superconducting domes due to a synergetic effect of structural transitions and a switching of the dominant orbital-selective pairing from $d_{xy}$ to $d_{z^2}$. Collectively, these findings pinpoint the vital role of electron correlations in the phonon-mediated pairing mechanism of bulk FeSe, and the $ab$-DMFT approach for quantitative evaluation of $T_{\text{c}}$ is expected to find broad applicability in other correlated electron systems.

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• Superconductivity
• Iron-based superconductors
• DFT+DMFT
• Density functional theory
• First-principles calculations