Quantum interference in 2D atomic-scale structures

Electrons occupying surface states on the close-packed faces of the noble metals form a two-dimensional (2D) electron gas that is accessible to the scanning tunneling microscope (STM). Using a cryogenic STM, we have observed quantum mechanical interference patterns arising from 2D electrons on the surface of Cu. These interference patterns can be artificially controlled by arranging individual Fe atoms into "quantum corrals" on the Cu surface. Quantum corrals behave qualitatively like 2D hard-wall boxes, but a quantitative understanding is obtained within a multiple scattering formalism. The scattering here is characterized by a complex phase shift which can be extracted from the electronic density pattern near a quantum corral.