Quasiparticle lifetime in macroscopically uniform Ag/Fe(100) quantum wells

Epitaxial Ag(100) films have been grown on highly perfect Fe(100) substrate s by deposition at low temperatures followed by annealing. Precise control of the deposition process results in film thicknesses of exactly N atomic l ayers (N an integer up to 39) over a macroscopic distance (similar to 1 mm) . The elimination of atomic layer fluctuation, which has been generally bel ieved to be impossible at such large thicknesses, allows us to observe atom ic-layer resolved quantum well states. Such states exhibit extremely narrow linewidths, which provide a direct measure of the quasiparticle lifetime.