Direct measurements of the<i>L</i>-gap surface states on the (111) face of noble metals by photoelectron spectroscopy

Abstract

We present a comprehensive photoemission study of the L-gap surface states of the (111) surfaces of Cu, Ag, and Au by high-resolution angle-resolved photoelectron spectroscopy (PES). With an angular resolution of about $\ensuremath{\Delta}\ensuremath{\theta}=\ifmmode\pm\else\textpm\fi{}0.15\ifmmode^\circ\else\textdegree\fi{}$ and an energy resolution of $\ensuremath{\Delta}E\ensuremath{\approx}3.5\mathrm{meV},$ our data establish new values for the intrinsic lifetime broadening and the dispersion relation of these surface states. We compare our photoemission results to recently published theoretical calculations and measurements by scanning tunneling spectroscopy (STS). In the case of the Au(111) state, we observe particular qualitative discrepancies in comparison to the STS data: the PES data show a split dispersion and Fermi surface, possibly caused by a spin-orbit interaction of the surface state electrons.