We have observed an unoccupied surface state on the Cu(110) surface using k-resolved inverse photoemission. It is located 2.5±0.2 eV above the Fermi level and disperses parabolically about the Y¯ 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¯ 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.

• Received 30 November 1984

DOI:https://doi.org/10.1103/PhysRevB.31.4745