Ab initio studies on interactions in K3 C60 under high pressure

Fullerene solids doped with alkali metals (A3C60, A = K, Rb, Cs) exhibit a superconducting transition temperature Tc as high as 40 K, and their unconventional superconducting properties have been a subject of debate. With the application of high pressure on K3C60 and Rb3C60, experiments demonstrate the decrease of Tc. In this paper, we focus on K3C60 and derive the structure of K3C60 under different pressures based on first-principles calculations, exploring the trends of Coulomb interactions at various pressures. By utilizing the maximally localized Wannier function approach, constrained density functional perturbation theory, and constrained random phase approximation, we construct a microscopic low-energy model near the Fermi level. Our results strongly indicate that, in the K3C60 system, as pressure increases, the effect of phonons is the key to intraorbital electron pairing. The phonon-driven superconducting mechanism is dominant at high pressure.