Evidence for a New Broadening Mechanism in Angle-Resolved Photoemission from Cu(111)

Abstract

High-resolution angle-resolved photoemission measurements on the $\mathrm{sp}$ surface state on Cu(111) show that its peak width increases on approaching the Fermi energy, a result contrary to usual expectations based on final-state lifetimes. The effect is explained in terms of inherent energy and/or momentum broadening of the surface-state wave function.