Investigation of the surface bands along the X̅ -M̅ line of the Cu(100) surface

Recent semiempirical linear combination of atomic orbital method (LCAO) calculations for the Cu surfaces of low Miller indices have given surface bands which agree very well with the available experimental data. These calculations indicate the existence of various surface states and resonances, in particular, in the s-d band region, which have not yet been experimentally observed. We have checked a part of these predictions by performing angle-resolved photoemission measurements along the X̅ -M̅ direction of the (100) surface, a direction that, to our knowledge, has not yet been investigated. Most of the predicted surface states and resonances have been actually observed and are in good agreement with the calculations. Furthermore, the calculated effective k-resolved density of states quantitatively reproduces the experimental photoemission spectra, as it results from the comparison that we have done at the high-symmetry points. The results reported in the present paper confirm the predictive ability of LCAO calculations performed with a carefully chosen parameter set and provide experimental evidence of several previously unknown surface states.