We present a detailed analysis of the band structure of the BiAg$_2$/Ag/Si(111) trilayer system by means of high resolution Angle Resolved Photoemission Spectroscopy (ARPES). BiAg2/Ag/Si(111) exhibits a complex spin polarized electronic structure due
to giant spin-orbit interactions. We show that a complete set of constant energy ARPES maps, supplemented by a modified nearly free electron calculation, provides a unique insight into the structure of the spin polarized bands and spin gaps. We also show that the complex gap structure can be continuously tuned in energy by a controlled deposition of an alkali metal.
We studied by angle-resolved photoelectron spectroscopy the strain-related structural transition from a pseudomorphic monolayer (ML) to a striped incommensurate phase in an Ag thin film grown on Pt(111). We exploited the surfactant properties of Bi t
o grow ordered Pt(111)-xMLAg-Bi trilayers with 0 < x < 5 ML, and monitored the dispersion of the Bi-derived interface states to probe the structure of the underlying Ag film. We find that their symmetry changes from threefold to sixfold and back to threefold in the Ag coverage range studied. Together with previous scanning tunneling microscopy and photoelectron diffraction data, these results provide a consistent microscopic description of the coverage-dependent structural transition.
The Bi/Si(111) (sqrt{3} x sqrt{3})R30 trimer phase offers a prime example of a giant spin-orbit splitting of the electronic states at the interface with a semiconducting substrate. We have performed a detailed angle-resolved photoemission (ARPES) stu
dy to clarify the complex topology of the hybrid interface bands. The analysis of the ARPES data, guided by a model tight-binding calculation, reveals a previously unexplored mechanism at the origin of the giant spin-orbit splitting, which relies primarily on the underlying band structure. We anticipate that other similar interfaces characterized by trimer structures could also exhibit a large effect.
