Surface states of clean and metal-overlayer-covered Cr(001) films

Electronic-structure calculations for a clean Cr(001) film and for Cr(001) films covered with Au, Pt, or Ir monolayers predict a surface band localized on the outer Cr layer near the Fermi level. The high density of surface states in the Au adsorption case may help explain the recent observation of 3-K superconductivity in Au-Cr-Au sandwiches. The stability of the surface band against overlayer adsorption indicates the necessity of refining the test usually used to identify spectroscopic peaks as surface states.