Mott localization in the correlated superconductor Cs3C60 resulting from the molecular Jahn-Teller effect

TL;DR

This paper investigates how Mott localization and the dynamic Jahn-Teller effect lead to insulating behavior in Cs3C60, emphasizing molecular phenomena's role in its electronic and magnetic properties.

Contribution

It provides experimental evidence from infrared spectroscopy showing the influence of the dynamic Jahn-Teller effect on the insulating state of Cs3C60.

Findings

Infrared spectroscopy reveals Jahn-Teller distortions.

Temperature-dependent line splitting indicates Jahn-Teller behavior.

Dynamic Jahn-Teller effect influences electronic properties.

Abstract

Cs3C60 is a correlated superconductor under pressure, but an insulator under ambient conditions. The mechanism causing this insulating behavior is the combination of Mott localization and the dynamic Jahn-Teller effect. We show evidence from infrared spectroscopy for the dynamic Jahn-Teller distortion. The continuous change with temperature of the splitting of infrared lines is typical Jahn-Teller behavior, reflecting the change in population of solid-state conformers. We conclude that the electronic and magnetic solid-state properties of the insulating state are controlled by molecular phenomena. We estimate the time scale of the dynamic Jahn-Teller effect to be above 10^(-11) s and the energy difference between the conformers less than 20 cm-1.