Insulating and Conducting Phases of RbC60

TL;DR

This study investigates the insulating and conducting phases of RbC60 through optical measurements, revealing a metastable insulating phase induced by quenching and a phase transition between conducting phases upon slow cooling.

Contribution

It provides direct optical evidence for a metastable insulating phase and identifies a phase transition between conducting phases in RbC60.

Findings

Quenching increases transmission indicating an insulating phase.

Slow cooling causes a transition between conducting phases.

Metastable insulating phase exists in RbC60.

Abstract

Optical measurements were performed on thin films of Rb$_{x}$C$_{60}$, identified by X-ray diffraction as mostly $x=1$ material. The samples were subjected to various heat treatments, including quenching and slow cooling from 400K. The dramatic increase in the transmission of the quenched samples, and the relaxation towards the transmission observed in slow cooled samples provides direct evidence for the existence of a metastable insulating phase. Slow cooling results in a phase transition between two electrically conducting phases.