Evidence for bandlike dispersion in ${\mathrm{K}}_{6}{\mathrm{C}}_{60}(110)$ films

Evidence for bandlike dispersion in $K_{6} C_{60} (110)$ films

A. Goldoni, L. Petaccia, G. Zampieri, S. Lizzit, C. Cepek, E. Gayone, J. Wells, and Ph. Hofmann

Phys. Rev. B 74, 045414 – Published 13 July 2006

Abstract

Using angle resolved photoemission we show that bandlike states in $K_{6} C_{60} (110)$ films at $40 K$ survive in spite of the strong electron-phonon coupling expected in fullerides that should give rise to polaron formation. The momentum dependence and the total bandwidth of the dispersing bands contributing to the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) features agree quite well with one-electron band structure calculations. While a crude estimation of the dimensionless electron-phonon coupling constant $λ$ , from the temperature dependence of the LUMO linewidth in photoemission spectra, seems to place $K_{6} C_{60}$ in an intermediate polaronic regime, the expected strong coupling to $K^{+}$ modes remains uncertain.