Institut für Theoretische Physik und Astrophysik, Universität Würzburg, Würzburg 97074, Germany.
Nat Commun. 2013;4:1620. doi: 10.1038/ncomms2617.
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.
二维电子系统在用于器件应用时，可能会由于局部库仑斥力而失去其导电性质，导致莫特绝缘状态。在三角形几何形状中，任何伴随的反铁磁自旋有序都可以通过几何失谐来阻止，这引发了关于“熔融”相的猜测，即自旋液体。在这里，我们表明，对于通过半导体上的外延原子吸附来实现三角形电子系统，这种自旋无序不会出现。我们的研究比较了相关电子晶格的理论模拟获得的电子激发谱与高分辨率光发射数据。我们发现，发生了一种不寻常的逐行反铁磁自旋排列，这在光发射谱中表现为自旋图案引起的特征“阴影带”。在由非磁性成分组成的受挫晶格中，磁序源自原子之间的长程电子跃迁。这一发现为控制表面磁性能提供了新的途径。
