  By means of band structure calculations within the density functional theory
and the generalized gradient approximation, we investigate the electronic
structure of self-organized Pt nanowires on the Ge(001) surface. In particular,
we deal with a novel one-dimensional surface state confined in the nanowire
array and clarify its origin. Due to large Pt contributions, the novel state is
rather a mixed Ge-Pt hybrid state than a confined Ge surface state. Moreover,
we compare our results to data from scanning tunneling microscopy.
