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 Si(111)5×2-Au and Si(557)-Au. As two-dimensional reference the Si(111)√3×√3-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 Si(111)5×2-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. Si(111)√3×√3-Au exhibits an electron pocket at Γ that changes its filling continuously with increasing Au coverage.