Electron-Lattice Interaction onα−Ga(010)

We have investigated the (010) surface of $\alpha -\mathrm{Ga}$ by angle-resolved photoemission and low energy electron diffraction. We find a surface state around the $\overline{C}$ point of the surface Brillouin zone. The electron-phonon coupling at this surface is very strong with an electron-phonon mass enhancement parameter of $\lambda =1.4\mathrm{}\pm 0.10$. Our spectra show high background intensity in a projected bulk band gap which cannot be accounted for by defect scattering and is therefore interpreted as indicating a nonquasiparticle behavior. Upon cooling the sample below 220 K we observe a phase transition accompanied by spectral changes near the Fermi level.