Optical evidence of metal-insulator phase transition in A 1C 60

Abstract

We have investigated the complete electrodynamic response of the newly discovered alkali fulleride linear polymers A 1C 60. We find clear evidence for a metal-insulator phase transition at low temperatures in Rb 1C 60 and Cs 1C 60, while the K-compound remains metallic at all temperatures. The possibility of a broken symmetry ground state due to the formation of a spin-density-wave for the Rb and Cs compound, as suggested by the magnetic properties, is discussed.