Electron-phonon coupling and temperature-dependent shift of surface states on Be(101\u3csup\u3e-\u3c/sup\u3e0)

The temperature dependence of two Schockley surface states (formula presented) and (formula presented) on (formula presented) located in a wide bulk projected band gap from (formula presented) to (formula presented) has been investigated with angle-resolved photoemission spectroscopy. The electron-phonon coupling of the surface states (formula presented) and (formula presented) at the zone boundary (formula presented) were determined using both Debye and Einstein phonon models. Based on fitting, this analysis indicates that the surface optical phonon mode located around 64 meV contributes most strongly to the electron-phonon coupling of the (formula presented) surface state, which is highly localized in the surface layer. The determined electron-phonon coupling parameter of (formula presented) and (formula presented) (0.647 and 0.491, respectively) is distinct from the bulk value (formula presented) Both surface states (formula presented) and (formula presented) are observed to shift linearly with the temperature, but in opposite directions at the rates of (formula presented) and (formula presented) respectively. The different behavior of the two surface states, with respect to both the electronic-phonon coupling and temperature-dependent shift of initial energy, is attributed to the higher surface charge localization of (formula presented) than (formula presented). © 2002 The American Physical Society