Surface resonances versus surface states on Fe(110)

The spin-dependent surface electronic structure of ferromagnetic Fe(110) is investigated experimentally and theoretically. Spin-resolved, inverse-photoemission results show a complex multipeak structure close to the Fermi level. Part of it is surface derived with an unexpected spin dependence and light-polarization dependence. The puzzling experimental findings are interpreted on the basis of a comprehensive theoretical analysis. Electronic slab calculations find surface-related features, caused by the crystal--vacuum interface, only well below the Fermi level. Calculations of the (inverse) photoemission intensities within the relativistic one-step model based on a bulk band structure, but with a realistic surface barrier, reveal an additional surface resonance around the Fermi level. Its nearly vanishing exchange splitting at Γ and abnormal energy dispersion behavior as a function of the wave vector parallel to the surface are in accordance with the experimental findings.