Spin pairing versus spin chains at Si(553)-Au surfaces

Density-functional theory is used to probe the spin structure of the Si(553)-Au surface. A diamagnetic sp(2) + p rehybridized structure, where the dangling bonds are either filled with two spin-paired electrons or are empty, is more favorable and in better agreement with experiment than the generally accepted spin-chain model. The shallow potential energy surface of Si(553)-Au, together with the ordered array of empty dangling bonds, suggests this surface as susceptible for spin polarization by doping, however.