Anisotropic spin gaps in BiAg2-Ag/Si(111)

Abstract

We present a detailed analysis of the band structure of the √ 3 × √ 3 R 30 • BiAg 2 /Ag/Si(111) trilayer system by means of high resolution Angle Resolved Photoemission Spectroscopy (ARPES). BiAg 2 /Ag/Si(111) exhibits a complex spin-polarized electronic structure due to giant spin-orbit interactions. We show that a complete set of constant energy ARPES maps, supplemented by a modified nearly free electron calculation, provides a unique insight into the structure of the spin-polarized bands and spin gaps. We also show that the complex gap structure can be continuously tuned in energy by a controlled deposition of an alkali metal.

Interaction Induced Staggered Spin-Orbit Order in Two-Dimensional Electron Gas

“…The nature of gap opening and multiple number of shadow bands are in detailed agreement with recent ARPES data on the surface state of BiAg 2 alloy deposited on the monolayres (MLs) of Ag/Au(111) heterostructure. [19,20] Similarly, along the diagonal direction, ∆ appears slightly above the Fermi level, and tiny hole-like pockets develop, as visible on the FS map in Fig. 2(e).…”

“…This is a difficult task as the electric field generated either by the broken inversion symmetry and/ or by the magnetic field itself naturally generates charge current perpendicular to the spin current, thus greatly hinders the spin transport. [12,13] Despite the discovery of giant SOC in a large class of condensed matter systems, [14][15][16][17][18][19][20] practical realization and device implementation of these concepts have thus posed challenging. [10,11] In this work, we introduce a theoretical proposal for generating and manipulating staggered spin-orbit entangled helical state via electronic interaction.…”

“…In the single-particle description of the system, the noninteracting FS is spin-polarized on the two-dimensional (2D) momentum space. For some systems, as in the surface state of BiAg 2 deposited on various substrates, [19,20] the FSs can yield a shape to generate dominant FS nesting, and hence an unstable one-body ground state. If two momenta across the nesting 'hot-spot' is connected by spin flips, it cannot support a charge density wave scenario.…”

Formation of the BiAg2 surface alloy on lattice-mismatched interfaces

“…Ni(111) supports spin-polarized electronic states and therefore the interplay between Rashba and exchange interactions could be investigated [28,29]. Although the BiAg 2 alloy has been previously grown on Si(111) [6][7][8], the Ag film thickness could be lowered and a Rashba surface state interface with a semiconductor substrate could be obtained.…”

“…The combined interest in their surface electronic structure and the limited number of substrates where these alloys could form on top have motivated the search for heavy metal alloys in thin films grown onto different substrates [5]. For example, BiAg 2 was obtained on Ag thin films grown onto semiconducting Si(111) aiming to bring the system one step closer to future technological applications [6][7][8]. The Ag film thickness was 10 ML, and hence the bulk character of the Ag film was already established.…”