0000000000711736
AUTHOR
M. Ellguth
Instability of the topological surface state in Bi$_2$Se$_3$ upon deposition of gold
Momentum-resolved photoemission spectroscopy indicates the instability of the Dirac surface state upon deposition of gold on the (0001) surface of the topological insulator Bi2Se3. Based on the structure model derived from extended x-ray absorption fine structure experiments showing that gold atoms substitute bismuth atoms, first-principles calculations provide evidence that a gap appears due to hybridization of the surface state with gold d states near the Fermi level. Our findings provide insights into the mechanisms affecting the stability of the surface state.
Exchange Splitting of a Hybrid Surface State and Ferromagnetic Order in a 2D Surface Alloy
Surface alloys are highly flexible materials for tailoring the spin-dependent properties of surfaces. Here, we study the spin-dependent band structure of a DyAg$_2$ surface alloy formed on an Ag(111) crystal. We find a significant exchange spin-splitting of the localized Dy 4f states pointing to a ferromagnetic coupling between the localized Dy moments at $40\,$K. The magnetic coupling between these moments is mediated by an indirect, RKKY-like exchange coupling via the spin-polarized electrons of the hole-like Dy-Ag hybrid surface state.