title: Excitation of coherent phonons in the one-dimensional Bi(114) surface.
abstract: We present time-resolved photoemission experiments from a peculiar bismuth surface, Bi(114). The strong one-dimensional character of this surface is reflected in the Fermi surface, which consists of spin-polarized straight lines. Our results show that the depletion of the surface state and the population of the bulk conduction band after the initial optical excitation persist for very long times. The disequilibrium within the hot electron gas along with strong electron-phonon coupling cause a displacive excitation of coherent phonons, which in turn are reflected in coherent modulations of the electronic states. Beside the well-known A(1g) bulk phonon mode at 2.76 THz, the time-resolved photoelectron spectra reveal a second mode at 0.72 THz which can be attributed to an optical surface phonon mode along the atomic rows of the Bi(114) surface.
authors.affiliation: Physics Institute, University of Zürich, Winterthurerstrasse 190, 8057 Zürich, Switzerland.
authors.forename: D
authors.initials: D
authors.lastname: Leuenberger
authors.forename: H
authors.initials: H
authors.lastname: Yanagisawa
authors.forename: S
authors.initials: S
authors.lastname: Roth
authors.forename: J H
authors.initials: JH
authors.lastname: Dil
authors.forename: J W
authors.initials: JW
authors.lastname: Wells
authors.forename: P
authors.initials: P
authors.lastname: Hofmann
authors.forename: J
authors.initials: J
authors.lastname: Osterwalder
authors.forename: M
authors.initials: M
authors.lastname: Hengsberger