Spin-orbit interaction in the photoemission spectra of noble metal surface states

By use of photoemission spectroscopy with high resolution in both energy and momentum, one is able to observe a considerable splitting of the Shockley-type surface state on the (111)-face of gold. This splitting exists over the complete two-dimensional Fermi surface of this surface state but disappears at normal emission. A comparison with fully relativistic density functional calculations proves that the splitting is caused by spin-orbit interaction, which-in combination with the lack of inversion symmetry at the surface-resolves the spin degeneracy of the surface state band. This paper gives a summary of recent experimental and theoretical investigations on the split Shockley state on Au(111). In addition, it will be demonstrated that the splitting is influenced by adsorbates, and it will be discussed why it has not been observed experimentally on other noble metals.