Electronic structure of atomic chains on vicinal Si(111)-Au

Unusual electronic states are found for gold-induced chain and ladder structures on vicinal Si(111) surfaces, such as $\mathrm{Si}\mathrm{}\left(111\right)5\times 2-\mathrm{Au}$ and Si(557)-Au. As two-dimensional reference the $\mathrm{Si}\mathrm{}\left(111\right)\mathrm{}\sqrt{3}\times \sqrt{3}-\mathrm{Au}$ surface is investigated. The highly stepped Si(557)-Au surface is metallic, despite an even electron count. That is explained by two half-filled, nearly degenerate bands. On the $\mathrm{Si}\mathrm{}\left(111\right)5\times 2-\mathrm{Au}$ surface we find a band that changes continuously from one dimensional at its maximum to two dimensional at its minimum. It exhibits a pseudogap within 0.3 eV of the Fermi level $E_F,$ where the spectral weight is strongly reduced. $\mathrm{Si}\mathrm{}\left(111\right)\mathrm{}\sqrt{3}\times \sqrt{3}-\mathrm{Au}$ exhibits an electron pocket at $\Gamma$ that changes its filling continuously with increasing Au coverage.