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"Surface electronic structure of Co thin films on Cu(111)"
M.A. Barral, A.M. Llois and M. Weissmann
Proc. of the Workshop "At the Frontiers of Condensed Matter II - Magnetism, Magnetic Materials, and their Applications", Buenos Aires, Argentina, June 22-26, 2004. Ed. C. Saragovi, J. Guevara, R. Weht, A.M. Llois and M.T. Causa
Physica B Condens. Matter. 354(1-4) (2004) 161-165
There has been some controversy regarding the Scanning tunneling microscopy (STM) spectra of Co overlayers on Cu(1 1 1). Recent experiments [Phys. Rev. Lett. 90 (2003) 236801; Phys. Rev. Lett. 92 (2004) 57202] find a peak 0.4 eV below the Fermi energy, at the onset energy of the Cu(1 1 1) surface state, while the previous work [Phys. Rev. Lett. 85 (2000) 4365] found two peaks, one 1 eV below the Fermi level and the other 0.5 eV above it. To address this problem we have performed both ab initio and parameterized tight-binding calculations for a Cu(1 1 1) slab coated with Co layers. The parameterized calculations allow larger unit cells and a better representation of the spill over region. The basis set used contains s, p and d orbitals and also extra s orbitals near the surface for the spill over. Our results for the local density of states at the site of the extra s orbital and at the Co surface site reproduce the feature at -0.4 eV, which also appears in pure Co slabs, and which is, therefore, not related to the Cu(1 1 1) surface state.
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