Figure 1

(Color online) (a) ARPES spectra (solid lines) measured at room temperature with $\text{He}\text{I}$ and SARPES spectra (triangles) measured at 100 K with $\text{He}\text{I}$ with spin polarization $U$ and $D$. (c) SARPES spectra with spin polarization $L$ and $R$. The common intensity scale is used for (a) and (c). [(b) and (d)] SARPES spectra in (a) and (c) from which the common, spin-independent polynomial background is subtracted and enlarged by a factor of 1.35. (e) Definition of the direction of spin polarization. (f) Second-derivative ARPES image (grayscale) and SARPES peak positions for $S$ and $S^{\prime }$.Reuse & Permissions

Figure 2

(Color online) (Left) The calculated band structure of bulk Ge along $\Gamma L\left(k_{\parallel }=0\right)$. Solid (dashed) lines represent occupied (unoccupied) states. Unoccupied states are shifted downwards in energy by 20.2 eV, which corresponds closely to the photon energy minus the band gap underestimated by the calculation. (Right) The surface reciprocal-lattice vectors (dashed arrows) and bulk and surface Brillouin zones. The solid arrow represents the umklapp process observed.Reuse & Permissions

Figure 3

(Color online) (a) Calculated band structure along $\overline{\Gamma }\overline{M}$ for the slab with 44 Ge layers. The radii of the circles are proportional to the net contribution of $\text{Ge}4p_x{p}_y$ from the first to 18th layers with spin oriented toward $U/D$. Thin lines indicate the projected bulk VB. (b) The same as (a) but with spin oriented along $z$. (c) The band structure calculated without SOC. The radii of the circles are proportional to the contribution of $\text{Ge}4p_x{p}_y$ from the first to 18th layers. (d) Layer- and spin-resolved partial charges of the $S$ state at $k_{\parallel }=-0.052{\text{Å}}^{-1}$ indicated by an arrow in (a). The zeroth layer corresponds to the Bi adlayer. The inset shows charge-density profile summed for the sixth- and seventh-layer Ge along $z$.Reuse & Permissions

Figure 4

Schematics for the roles of atomic and Rashba SOI.Reuse & Permissions