Creating anisotropic spin-split surface states in momentum space by molecular adsorption

Abstract

In this ab initio study we demonstrate that molecular adsorption on a surface Rashba system can be used to modulate the surface electronic structure in different momentum space directions, i.e., to create anisotropic spin splittings in k space. This effect is rooted in the asymmetric adsorption of the molecules on the surface in a hollow site which breaks the surface symmetry. More specifically, we demonstrate that the physisorbed NH 3 has a small influence on the surface Rashba states and only gives rise to variations of the surface state Rashba parameters up to a factor of 1.4 over the surface Brillouin zone. In contrast, the chemisorption of BH 3 leads to variations of the Rashba parameter by more than a factor of 2.5. Consequently, the anisotropy of the Rashba-split-surface states induced by molecular adsorption also gives rise to a modulation of the surface state spin texture, i.e., the out-of-plane spin polarization varies along different k directions by up to 70% for the occupied states. This offers the possibility to change the spin direction from in-plane to predominantly out-of-plane by modifying the electronic momentum by 90°.

Selective control of surface spin current in topological pyrite-type OsX2 (X = Se, Te) crystals

“…The significant inplane d x 2 −y 2 character leads to a small band splitting in the S3 band. We note that similar spin splitting behavior has been realized in layered materials with doped surface where the surface symmetry is broken by dopants [47]. Here we find that symmetry breaking at the pristine pyrite surface can achieve the same effect by inducing different orbital screening along each high symmetry line.…”

Spin- and Angle-Resolved Photoemission Study of the Alq3/Co Interface

“…Moreover, possible modifications of the surface band structure of the ferromagnetic materials caused by the adsorption of organic molecules have also been disregarded so far. The latter could reveal a new way to control the spin-dependent electronic structure of ferromagnetic surfaces by adsorption of organic molecules as recently demonstrated for spin-textured surfaces. − …”

Modification of Pb quantum well states by the adsorption of organic molecules

“…This resulted in a comprehensive understanding of metalorganic hybrid systems and paved the way towards controlling the structural and electronic properties of molecular monolayer films on surfaces, for instance by alkali metal doping of organic monolayer films [12][13][14][15] or by the formation of heteromolecular systems containing two different types of molecules [16][17][18][19][20][21]. More recently, it was even demonstrated that the adsorption of organic molecules can lead to a severe modification of the occupied part of the surface band structure of topological insulators or Rashba-type surface alloys [22][23][24][25][26]. In particular, it was shown for a PbAg 2 surface alloy that only local σ-like bonds between functional molecular groups and surface atoms are strong enough to alter the surface band structure.…”