Electronic Correlations Stabilize the Antiferromagnetic Mott State in Cs3C60

Cs3C60 in the A15 structure is an antiferromagnet at ambient pressure in contrast with other super-conducting 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 antiferro-magnetic 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.