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

Electronic structure calculations for a clean Cr(001) film and for 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 3K 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.