Integrity of quantum-well resonances in metallic overlayers

Spin-polarized quantum-well states in Ag/Fe(001) have been studied by ab initio electronic structure calculations and spin-resolved inverse photoemission experiments. The calculations indicate that the quantum well energies make a continuous transition across the border separating discrete and resonant levels, and we find excellent agreement between predicted and measured sp quantum-well states, including majority-spin resonances previously unobserved in this system. These are found to exhibit unusual behavior, narrowing as they move further into the continuum energy range. We present a simple analysis based upon the phase-accumulation model which captures the essential physics. With increasing Ag coverage the resonance widths are shown to reduce in line with level spacings, indicating the quantum-well levels retain their integrity in thick films. © 1996 The American Physical Society.