Electronic Correlations Stabilize the Antiferromagnetic Mott State in Cs3C60

Cs3C60 in the A15 structure is an antiferromagnet at ambient pressure in contrast with other superconducting trivalent fullerides. Superconductivity is recovered under pressure and reaches the highest critical temperature of the family. Comparing density-functional calculations with generalized gradient approximation to the hybrid functional of Heyd, Scuseria, and Ernzerhof, which includes a suitable component of exchange, we establish that the antiferromagnetic state of Cs3C60 is not due to a Slater mechanism, and it is stabilized by electron correlation. Pressure reduces the stability of the antiferromagnetic state. Our findings corroborate previous analyses suggesting that the properties of this compound can be understood as the result of the interplay between electron correlations and Jahn-Teller electron-phonon interaction.