Electronic properties of K-doped ${\mathrm{C}}_{60}$(111): Photoemission and electron correlation

High-resolution photoemission provides the signatures of ${\mathrm{K}}_3$${\mathrm{C}}_{60}$(111), ${\mathrm{K}}_4$${\mathrm{C}}_{60}$, ${\mathrm{K}}_6$${\mathrm{C}}_{60}$, and the dilute solid solution of K in ${\mathrm{C}}_{60}$(111), showing the effects of electron-electron correlation in all of the K-${\mathrm{C}}_{60}$ phases. ${\mathrm{K}}_3$${\mathrm{C}}_{60}$(111) is a metal with a distinct Fermi-level cutoff but with spectral broadening near ${\mathit{E}}_{\mathit{F}}$ not predicted by band calculations. ${\mathrm{K}}_4$${\mathrm{C}}_{60}$ is an insulator, although band calculations predict metallic character. Photoemission and low-energy-electron-diffraction results demonstrate kinetically limited growth for K-${\mathrm{C}}_{60}$ films produced by vapor deposition.