Figure 1

(a) 1PPE map and (b),(c) 2PPE maps of the commensurate (a),(b) and incommensurate (c) Bi monolayer on Cu(111). For generation of the full angle distribution from about $-45°$ to $+45°$ a tilting of the sample with respect to analyzer and laser light source is required. This results in a modification of the effective polarization of the laser light impinging on the sample surface and leads to the strong asymmetry in the photoemission spectra. The band bottom of the occupied QW state and the crossings of the spin-orbit split unoccupied QW states are marked with white arrows. (d) Schematic of the [2012] Bi monolayer on Cu(111). (e) Brillouin zone scheme for the Bi monolayer (red or gray) on Cu(111) (black).Reuse & Permissions

Figure 2

Calculated band structure for commensurate monolayer of Bi on Cu(111). States marked in red (or gray) and blue (or dark gray) are Bi-derived unoccupied and occupied QW states, Cu states are shown in black. The size of the symbol is a measure of the weight of the states in the vacuum. For better visibility, the weight of the occupied states (blue) is multiplied by a factor 5. Cuts through the charge densities of three Bi states from the $\overline{\Gamma }$ point are shown: at the left, the (occupied) state at $E-E_F=-1.0\mathrm{eV}$ and, at the right, two unoccupied states at $E-E_F=2.1$ and 2.7 eV. With increasing energy the weight of the states in the vacuum can be seen to increase. The cuts show the upper eight Cu layers and go through the two Bi atoms in the unit cell. In the band structure, the Cu surface state from the other side of the film is visible as black circles.Reuse & Permissions

Figure 3

Direct comparison of experimental and theoretical data sets. (a) and (b) show the spin split QW state in the commensurate structure around 2.7 eV in $\overline{\Gamma }\mathrm{\text{−}}\overline{M}$ and $\overline{\Gamma }\mathrm{\text{−}}\overline{K}$ directions with the calculated $\overline{\Gamma }\mathrm{\text{−}}{\overline{X}}_1$ and $\overline{\Gamma }\mathrm{\text{−}}{\overline{X}}_2$ directions, respectively. (c) and (d) show the spin split QW state around 2.1 eV in the incommensurate structure with the according calculated data. Note that the $\overline{\Gamma }\mathrm{\text{−}}\overline{K}$ and $\overline{\Gamma }\mathrm{\text{−}}\overline{M}$ directions of the clean Cu substrate correspond to two possible directions in the Bi overlayer system.Reuse & Permissions