A Strategy to Create Spin-Split Metallic Bands on Silicon Using a Dense Alloy Layer

Abstract

To exploit Rashba effect in a 2D electron gas on silicon surface for spin transport, it is necessary to have surface reconstruction with spin-split metallic surface-state bands. However, metals with strong spin-orbit coupling (e.g., Bi, Tl, Sb, Pt) induce reconstructions on silicon with almost exclusively spin-split insulating bands. We propose a strategy to create spin-split metallic bands using a dense 2D alloy layer containing a metal with strong spin-orbit coupling and another metal to modify the surface reconstruction. Here we report two examples, i.e., alloying reconstruction with Na and Tl/Si(111)1 × 1 reconstruction with Pb. The strategy provides a new paradigm for creating metallic surface state bands with various spin textures on silicon and therefore enhances the possibility to integrate fascinating and promising capabilities of spintronics with current semiconductor technology.

Purely one-dimensional bands with a giant spin-orbit splitting: Pb nanoribbons on Si(553) surface

“…Systems which combine a semiconducting substrate and surface bands crossing the Fermi level are much less common. These include Pb/Ge(111)7, different reconstructions of Si1219, vicinal silicon surfaces with Au-induced ordering82223 and Si(557)-Pb18. The latter system is similar to that reported here, however, Δ k F  = 0.2 Å −1 is observed only at temperatures below 78 K where Fermi nesting occurs36.…”

“…Among various systems studied up to now and fulfilling some of the above criteria are semiconductors with their surface states Bi 2 Se 3 17, BiTeI9, metal overlayers on semiconducting substrates as Pb/Ge7 or Si(557)-Pb18, reconstructions of Si(111) induced by different elements1219 and vicinal silicon surfaces ordered by the presence of Au atomic chains820212223. Nanostructures of the latter group have one-dimensional (1D) character and as such they can reveal an extra advantage – a strong suppression of spin-orbit scattering2425.…”

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

“…4(e). This different spin splitting of the hybrid bands S1 and S2 along both high symmetry directions can be attributed to a hexagonal warping of the Fermi contour which has already been observed for spin-textured surfaces states in topological materials and Rashba-type surface alloys 13,32,[75][76][77][78][79][80][81] . In our adsorbate system, the Fermi surface warping can be explained by the threefold (p3m1) symmetry of the SnAu2/Au(111) surface alloy with an additional in-plane inversion asymmetry 13,79 leading to the Fermi contour of S1 and S2 as schematically shown in Fig.…”

Unconventional dc Transport in Rashba Electron Gases

“…Recently, intense research efforts [2] have been devoted to twodimensional materials with broken inversion symmetry, where the SO strength, parametrized by a characteristic energy scale E 0 , can be tuned by means of external conditions (electric fields, gating, doping, pressure, strain, etc.). In most of these systems (for example, surface alloys [3][4][5][6][7][8][9], layered bismuth tellurohalides [10][11][12][13][14][15][16], HgTe quantum wells [17], and interfaces between complex oxides [18][19][20][21][22][23][24][25][26][27][28][29][30][31][32]) the total charge carrier density n can be tuned down to very small concentrations, implying very small Fermi energies E F . Although the high-density (HD) regime E F ≳ E 0 has been widely investigated [2,[33][34][35][36][37][38], relatively less attention has been paid to the opposite regime of dominant SO (DSO), E 0 ≳ E F .…”