Observation of an unoccupied surface state on Cu(110) by inverse photoemission

Abstract

We have observed an unoccupied surface state on the Cu(110) surface using k-resolved inverse photoemission. It is located 2.5\ifmmode\pm\else\textpm\fi{}0.2 eV above the Fermi level and disperses parabolically about the Y\ifmmode\bar\else\textasciimacron\fi{} point of the surface Brillouin zone with an effective mass of ${m}^{\mathrm{*}}$/m=1.1. These results, when considered along with photoemission data from the Y\ifmmode\bar\else\textasciimacron\fi{} gap, represent the first definitive observation of two crystal-induced surface states in the same bulk band gap of a metal. The origin of the two states is discussed in terms of a two-band model.