PHONON CONTRIBUTION TO QUASI-PARTICLE LIFETIMES IN CU MEASURED BY ANGLE-RESOLVED PHOTOEMISSION

The line shape of the photoelectron spectrum emitted from the sp-derived surface state at on Cu(111) is investigated. The line shape is Lorentzian, and the temperature dependence of the width is linear, varying from 30 meV at 30 K to 75 meV at 625 K. Less than 5-meV variation with binding energy is observed. The temperature dependence is explained as the phonon contribution to the inverse hole lifetime, predicted to be 2kbT allowing the determination that the electron-phonon mass enhancement parameter =0.140.02 for this surface state at . This is compared to =0.15 reported as an average over the bulk Fermi surface. © 1995 The American Physical Society.