Electron-lattice interaction on α-Ga(010)

We have investigated the (010) sur-face of alpha-Ga by angle-resolved photoemission and low energy electron diffraction. We find a surface state around the 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 +/- 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. [S0031-9007(98)06909-9].