title: Magnetic order in a frustrated two-dimensional atom lattice at a semiconductor surface.
abstract: Two-dimensional electron systems, as exploited for device applications, can lose their conducting properties because of local Coulomb repulsion, leading to a Mott-insulating state. In triangular geometries, any concomitant antiferromagnetic spin ordering can be prevented by geometric frustration, spurring speculations about 'melted' phases, known as spin liquid. Here we show that for a realization of a triangular electron system by epitaxial atom adsorption on a semiconductor, such spin disorder, however, does not appear. Our study compares the electron excitation spectra obtained from theoretical simulations of the correlated electron lattice with data from high-resolution photoemission. We find that an unusual row-wise antiferromagnetic spin alignment occurs that is reflected in the photoemission spectra as characteristic 'shadow bands' induced by the spin pattern. The magnetic order in a frustrated lattice of otherwise non-magnetic components emerges from longer-range electron hopping between the atoms. This finding can offer new ways of controlling magnetism on surfaces.
authors.affiliation: Institut für Theoretische Physik und Astrophysik, Universität Würzburg, Würzburg 97074, Germany.
authors.forename: Gang
authors.initials: G
authors.lastname: Li
authors.forename: Philipp
authors.initials: P
authors.lastname: Höpfner
authors.forename: Jörg
authors.initials: J
authors.lastname: Schäfer
authors.forename: Christian
authors.initials: C
authors.lastname: Blumenstein
authors.forename: Sebastian
authors.initials: S
authors.lastname: Meyer
authors.forename: Aaron
authors.initials: A
authors.lastname: Bostwick
authors.forename: Eli
authors.initials: E
authors.lastname: Rotenberg
authors.forename: Ralph
authors.initials: R
authors.lastname: Claessen
authors.forename: Werner
authors.initials: W
authors.lastname: Hanke
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