Events at Physics
The broken bond orbitals are so localized at the step edges that they become fully spin-polarized, similar to isolated broken bonds (Pb centers). Density functional theory predicts a spin-polarized ground state which is closely coupled to the formation of a superlattice (neither can exist without the other) . This resembles the situation in complex oxides (HiTc superconductors, multiferroics), where the spin, charge, and lattice degrees of freedom are strongly coupled and make it difficult to find a simple approximation of their electronic structure.
Two-photon photoemission spectroscopy  and scanning tunneling spectroscopy  provide support for spin-polarized silicon atoms by probing their characteristic minority spin state.
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4. P. C. Snijders et al., Spectroscopic evidence for spin-polarized silicon atoms on Si(553)-Au, submitted.