Quantum interference is a coherent quantum phenomenon that takes place in confined geometries. Using spin-polarized scanning tunneling microscopy, we found that quantum interference of electrons causes spatial modulation of spin polarization within a single magnetic nanostructure. We observed changes in both the sign and magnitude of the spin polarization on a subnanometer scale. A comparison of our experimental results with ab initio calculations shows that at a given energy, the modulation of the spin polarization can be ascribed to the difference between the spatially modulated local density of states of the majority spin and the nonmodulated minority spin contribution.

The state of the art ab initio calculations of quantum mirages, the spin polarization of surface-state electrons, and the exchange interaction between magnetic adatoms in Cu and Co corrals on Cu(111) are presented. We find that the spin polarization of the surface-state electrons caused by magnetic adatoms can be projected to a remote location and can be strongly enhanced in corrals, compared to an open surface. Our studies give clear evidence that quantum corrals could permit one to tailor the exchange interaction between magnetic adatoms at large separations.

Combined experimental and ab initio studies show that the surface-state-mediated adatom-step and adatomadatom interactions are the driving forces for the self-organization of Fe adatoms on vicinal Cu͑111͒ surfaces at low temperatures. Our scanning tunneling microscope observations and the kinetic Monte Carlo simulations reveal the self-organization of Fe adatoms into atomic strings. The interatomic separation ͑1.2 nm͒ in the strings is not determined by the nearest-neighbor distance ͑0.26 nm͒ of the Cu atoms along the step edge but by the wavelength of the surface-state charge density oscillations.

No abstract

We demonstrate the one-dimensional ordering of Co and Fe atoms employing supramolecular templates. Our low-temperature scanning tunneling microscopy observations reveal how individual adatoms spontaneously align with a preferred ϳ25 Å next-neighbor spacing in self-assembled methionine nanogratings on Ag͑111͒. For Co strings the pertaining equilibrium statistics and dynamics were monitored to assess the underlying long-range interactions with their anisotropic energy landscape. The effect of the surface-state electron quantum confinement on the atomic self-alignment is revealed by tunneling spectroscopy mapping and ab initio calculations.