Looking into Thin Metal Films: Surface and Interface Effects on Quantum Confined Electrons

by Paolo Moras (Istituto di Struttura della Materia - CNR)

Tuesday 23 Jun 2015, 13:00 → 14:00 Europe/Berlin

AER19/3.11 (European XFEL GmbH)

Surface and interface act on the valence electrons of a ultrathin metal film as confining potential walls, giving rise to a set of discrete quantum well states, in close analogy with the particle-in-a-box picture. These two-dimensional standing waves, extended in the whole film thickness, are effective, though indirect, probes of surface and interface interactions, which influence their energy-momentum band dispersion. I will show how relevant these effects are on the basis of angle-resolved photoemission data for substrate-supported thin metal films. In the simplest cases, deviations from the expected quantum well band dispersion can be linked to symmetry-selective hybridization between film and substrate states. A more complex scenario emerges in the presence of heavy elements and ferromagnetic metals. Quantum well states display asymmetric dispersion, in contrast to the electron behavior in centro-symmetric systems. Theoretical analysis ascribes the observed effects to the combination of large exchange and Rashba spin-orbit fields, that characterize ferromagnetic layers and heavy elements. These findings will be discussed in connection with potential spintronics applications.