Cesium graphite intercalation compound study from angle-resolved photoemission spectroscopy

We present here the first experimental determination of the band structure of a graphite intercalation compound from angle-resolved photoemission spectroscopy (ARPES) using synchrotron radiation. It is shown that the equilibrium surface composition of the sample is different from the bulk composition. The band structures of two different surface compounds are observed, with a symmetry corresponding, respectively, to ${\mathrm{CsC}}_8$ and ${\mathrm{CsC}}_6$. The donor s level seems to be empty in each case, and the observed band structure is in excellent agreement with recent theoretical calculations for ${\mathrm{CsC}}_8$.