Visualization of the Molecular Jahn-Teller Effect in an Insulating K₄C₆₀ Monolayer
2005
Wachowiak, A. | Yamachika, R. | Khoo, K. H. | Wang, Y. | Grobis, M. | Lee, D.-H. | Louie, Steven G. | Crommie, M. F.
We present a low-temperature scanning tunneling microscopy (STM) study of K[subscript x]C₆₀ monolayers on Au(111) for 3 </= x </= 4. The STM spectrum evolves from one that is characteristic of a metal at x = 3 to one that is characteristic of an insulator at x = 4. This electronic transition is accompanied by a dramatic structural rearrangement of the C₆₀ molecules. The Jahn-Teller effect, a charge-induced mechanical deformation of molecular structure, is directly visualized in the K₄C₆₀ monolayer at the single-molecule level. These results, along with theoretical analyses, provide strong evidence that the transition from metal to insulator in K[subscript x]C₆₀ monolayers is caused by the Jahn-Teller effect.
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