Structure and electronic properties of the (3×3)R30∘SnAu2<

Abstract

We have investigated the atomic and electronic structure of the !√3 × √3% 30° SnAu2/Au(111) surface alloy. Low energy electron diffraction and scanning tunneling microscopy measurements show that the native herringbone reconstruction of bare Au (111) surface remains intact after formation of a long range ordered !√3 × √3% 30° SnAu2/Au(111) surface alloy. Angle-resolved photoemission and two-photon photoemission spectroscopy techniques reveal Rashba-type spin-split bands in the occupied valence band with comparable momentum space splitting as observed for the Au(111) surface state, but with a hole-like parabolic dispersion. Our experimental findings are compared with density functional theory (DFT) calculation that fully support our experimental findings. Taking advantage of the good agreement between our DFT calculations and the experimental results, we are able to extract that the occupied Sn-Au hybrid band is of (s, d)-orbital character while the unoccupied Sn-Au hybrid bands are of (p, d)-orbital character. Hence, we can conclude that the Rashba-type spin splitting of the hole-like Sn-Au hybrid surface state is caused by the significant mixing of Au dto Sn s-states in conjunction with the strong atomic spin-orbit coupling of Au, i.e., of the substrate.

Exchange Splitting of a Hybrid Surface State and Ferromagnetic Order in a 2D Surface Alloy

“…We find a triangular shaped emission feature for both binding energies along the Γ MAg direction, while the emission feature at the Γ KAg direction exhibits a ring-like shape at E B = 0.8 eV which transforms into a dot-like emission at E B = 0.2 eV. This energy and momentum dependent spectral intensity at the KAg -point is consistent with a parabolic dispersion of a hole-like state as expected for a hybrid surface state of a heavy metal/rare-earth alloy formed on a noble metal surface [4][5][6][7][8][9]15 .…”

“…The shape of the hybrid band is indicated by a green curve as a guide to the eye. It clearly reveals the dispersion of a hole-like state, in analogy to all hybrid surface states reported for surface alloys on fcc(111) noble metal surfaces [4][5][6][7][8][9]15 . In addition, we observe the appearance of a second band at larger binding energies indicated by a red curve as well as a non dispersive state close to E F .…”

“…A particular effort has been devoted to reduce the size of the spintronic assemblies, which allows one to generate and manipulate spin-polarized charge carriers on ever smaller length scales ultimately down to the single layer limit 1-3 . In this context, a highly tunable class of materials are surface alloys consisting of heavy metal and noble metal atoms [4][5][6][7][8][9] . These 2D binary systems can be fabricated in long-range ordered superstructures on noble metal surfaces in which every third surface atom of the noble metal host material is replaced by a heavy metal atom (Pb, Bi and Sb) of the alloy species.…”

“…For spintronic applications, these binary systems are highly intriguing materials due to their spin-dependent band structure. The direct hybridization between both atomic species of the surface layer and underlying substrate layers results in the formation of a new holelike hybrid surface state showing a Rashba-type spin splitting [4][5][6][7][8][9] . Crucially, the magnitude of this Rashbatype spin splitting therein depends on the atomic spinorbit coupling strength 10,11 as well as on the vertical relaxation 5,12 of the surface atoms.…”

A case study for the formation of stanene on a metal surface

“…When the temperature is carefully increased further to 455 K, a stretched hexagon structure appears, named as ffiffi ffi 7 p phase (discussed below). Finally, when the temperature is raised beyond 470 K, a ffiffi ffi 3 p superstructure appears 23 . All these superstructures are stable at room temperature after post-deposition annealing.…”