Surface electron bands and Fermi surface of Be(0001)

The three surface electronic states of Be(0001) have different symmetry as probed by high-resolution angle resolved photoemission (ARPES) with variable polarization synchrotron radiation. We probed the two ($\overline{\Gamma }\text{−}\overline{M}$ and $\overline{\Gamma }\text{−}K$) high symmetry directions and measured the Fermi surface cuts. Electron states of even or odd symmetry with respect to the crystal (and/or surface) mirror planes contribute to the photoemission intensity as a function of the light polarization and experimental geometry. The effects of the large surface relaxation of Be(0001) are directly reflected in the Fermi surface.

Figure 1

(Color online) Energy dispersion curves for $h\nu =32.5\mathrm{eV}$ along $\overline{\Gamma }\text{−}\overline{M}$ and $\overline{\Gamma }\text{−}\overline{K}$ measured with horizontal (↔) (a), (b) and vertical (↕) (c), (d) polarization.

Figure 2

(Color online) Comparison of the spectra measured with different polarizations and integrated over the regions marked with gray (blue) rectangles in Fig. 1 for the $\overline{\Gamma }$ surface state (SS) and $\overline{M}$ surface state and surface resonance (SS and SR) along $\overline{\Gamma }\text{−}\overline{M}$ (a), (b) and $\overline{\Gamma }\text{−}\overline{K}$ (c), (d); full black lines correspond to the horizontal $\left(H\right)$ and dashed (red) lines to the vertical $\left(V\right)$ polarization.

Figure 3

(Color online) Energy dispersion curves for $h\nu =86\mathrm{eV}$ along $\overline{\Gamma }\text{−}\overline{M}$ and $\overline{\Gamma }\text{−}\overline{K}$ measured with horizontal (↔) (a), (b) and vertical (↕) (c), (d) polarization.

Figure 4

(Color online) Comparison of the spectra measured with different polarizations and integrated over the regions marked with gray (blue) rectangles in Fig. 3 for the $\overline{\Gamma }$ surface state (SS) and $\overline{M}$ surface state and surface resonance (SS and SR) along $\overline{\Gamma }\text{−}\overline{M}$ (a), (b) and $\overline{\Gamma }\text{−}\overline{K}$ (c), (d); black full lines correspond to the horizontal $\left(H\right)$ and dashed (red) lines to the vertical $\left(V\right)$ polarization.

Figure 5

(Color online) Fermi surface cuts measured with $h\nu =32.5\mathrm{eV}$ and horizontal $\left(H\right)$ (a) and vertical $\left(V\right)$ (b) polarizations, their sum $(H+V)$ (c) and difference $(H-V)$ (d); Fermi surface cuts measured with $h\nu =86\mathrm{eV}$ and horizontal (f) and vertical (g) polarizations, their sum $(H+V)$ (h) and difference $(H-V)$ (i); the hexagons in (a)–(d) and (f)–(i) delimit the first surface Brillouin zone; the arcs marked $32.5\mathrm{eV}$ in (e) and $86\mathrm{eV}$ in (j) denote the $k$-space area probed in our experiment; for more details see the text.