Lifetime of surface states on (0001) surfaces of lanthanide metals

Abstract

We have studied the electronic structure of surface states on (0001) surfaces of Gd, Ho, and Lu films with scanning-tunneling spectroscopy at low temperature (10 K). The ${5d}_{{z}^{2}}$-like surface states have a small dispersion and exhibit magnetic exchange splittings that are proportional to the $4f$-spin moment, being largest for Gd and zero for Lu. The surface state in Lu lies directly at the Fermi energy, resulting in a sharp peak in the tunneling spectrum. A line-shape analysis of the tunneling spectra reveals linewidths and, hence, lifetimes of surface-state electrons governed by electron-phonon and electron-electron scattering.