Epitaxial sub-monolayer assemblies of metal atoms on semiconductor surfaces represent versatile low-dimensional model systems with tunable electronic properties, which allow systematic investigations of prototypical many-body and interaction phenomena. In this project we will utilize such adatom structures for detailed studies of the effects of spin-orbit coupling in the presence of strong electronic correlations. This concerns in particular the interplay of Hubbard and spin-orbit physics in 2D triangular (and hence frustrated) lattices as well as the effect of spin-orbit interaction on the Tomonaga-Luttinger liquid behavior of atomic nanowires. Additional questions concern the possibility of topological superconductivity in triangular 2D layers and the occurrence of magnetic edge states in honeycomb lattice-based 1D structures. For this purpose we will study the microscopic electronic structure of prototypical and new 2D and 1D adatom systems by measuring the single-particle excitation spectra, in k-space by angle-resolved photoelectron spectroscopy (ARPES) and locally in real space by scanning tunneling microscopy/spectroscopy (STM/STS). This approach exploits the tunability of the surface electronic properties by variation of atomic constituents and by doping. The experimental research program will be guided and supported by close collaboration with theory.
[C03.2] J. Aulbach, J. Schäfer, S. C. Erwin, S. Meyer, C. Loho, J. Settelein, and R. Claessen, Evidence for long-range spin order instead of a Peierls transition in Si(553)-Au chains, Phys. Rev. Lett. 111, 137203