The alkali-doped fulleride ${\mathrm{Cs}}_3{\mathrm{C}}_{60}$, crystallized in the space group $Fm\overline{3}m$ or $Pm\overline{3}n$, exhibits unconventional $s$-wave superconductivity under pressure with a maximum $T_c\sim 38$ K. Recently, a new primitive-cubic-structured ${\mathrm{Cs}}_3{\mathrm{C}}_{60}$ phase corresponding to the space group $Pa\overline{3}$ has been reported (Peng et al., arXiv:2208.09429), and the authors observed superconductivity at ambient pressure. Using density functional theory (DFT) calculations, we show that the proposed $Pa\overline{3}$ structure is not stable under ionic relaxation, but transforms into the fcc structure. We study the normal and superconducting states of the stable fcc phase at different temperatures and volumes using DFT plus dynamical mean-field theory in the Nambu formalism. As the temperature increases, the transition between superconductor and normal metal (Mott insulator) at small (big) volume is found to be second (first) order. The recently developed maximum entropy analytic continuation method for the anomalous self-energy is used to study the momentum-resolved spectra and optical conductivity.

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• Optical conductivity
• Superconducting gap
• Superconducting order parameter
• Superconducting phase transition
• Fullerenes
• Strongly correlated systems
• Unconventional superconductors
• Angle-resolved photoemission spectroscopy
• Dynamical mean field theory