Electronic correlations stabilize the antiferromagnetic Mott state in Cs$_3$C$_{60}$

TL;DR

This study demonstrates that electron correlations, rather than a Slater mechanism, stabilize the antiferromagnetic Mott state in Cs₃C₆₀, and pressure induces a transition to a metallic state, highlighting the importance of electron interactions.

Contribution

The paper shows that electron correlations stabilize the antiferromagnetic state in Cs₃C₆₀, contrasting with previous Slater mechanism assumptions, and reproduces pressure-induced metallization using hybrid functional calculations.

Findings

Electron correlations stabilize the antiferromagnetic Mott state.

Pressure induces a transition from antiferromagnetic insulator to metal.

Hybrid functional calculations reproduce experimental pressure effects.

Abstract

Cs$_3$C$_{60}$ 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 HSE, which includes a suitable component of exchange, we establish that the antiferromagnetic state of Cs$_3$C$_{60}$ is not due to a Slater mechanism, and it is stabilized by electron correlation. HSE also reproduces the pressure-driven metalization. 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.