Electron-phonon interaction of one-dimensional and two-dimensional surface states in indium adlayers on the Si(111) surface

Abstract

We performed angle-resolved photoelectron spectroscopy measurements on one- and two-dimensional (1D and 2D) metallic surface states in indium layers on the Si(111) surface as a function of temperature. The temperature dependence of surface-state energy widths was used to estimate the electron-phonon coupling constant $\ensuremath{\lambda}$. The 2D metallic surface states of the $\sqrt{7}\ifmmode\times\else\texttimes\fi{}\sqrt{3}$-In layer above one monolayer exhibit $\ensuremath{\lambda}=0.8\ensuremath{\sim}1.0$, similar to the value of bulk indium 0.9. This is discussed in the light of a recent structure model with a double indium layer and the relatively high superconducting transition temperature of this surface. On the other hand, the $\ensuremath{\lambda}$'s of two 1D surface states of the 4 $\ifmmode\times\else\texttimes\fi{}$ 1-In surface with one monolayer of indium are much higher than that of $\sqrt{7}\ifmmode\times\else\texttimes\fi{}\sqrt{3}$-In, reaching 1.8, which is the largest ever reported for a surface state. The origin of the enhanced electron-phonon coupling and its relationship to the charge-density-wave phase transition of this surface are discussed.