  We have studied the interplay of a giant spin-orbit splitting and of quantum
confinement in artificial Bi-Ag-Si trilayer structures. Angle-resolved
photoelectron spectroscopy (ARPES) reveals the formation of a complex
spin-dependent gap structure, which can be tuned by varying the thickness of
the Ag buffer layer. This provides a means to tailor the electronic structure
at the Fermi energy, with potential applications for silicon-compatible
spintronic devices.
