Giant Friedel Oscillations on the Beryllium(0001) Surface
Large-amplitude electron density oscillations were observed on a Be(0001) surface by means of variable-temperature scanning tunneling microscopy. Fourier transforms of the images showed a ring of radius 2kF, where kF is the Fermi wave vector of the Be(0001) surface state. This wavelength was expected from Friedel oscillations caused by electronic screening of surface defects, but the amplitude of the waves for energies near the Fermi energy was anomalously large and inconsistent with the Friedel concept of screening. The enhanced amplitude of the waves must be a many-body effect, either in the electron gas (possibly an incipient charge density wave) or in the response of the lattice (electron-phonon coupling).
Sprunger
PT
P. T. Sprunger, L. Petersen, E. Laegsgaard, F. Besenbacher, Institute of Physics and Astronomy, University of Aarhus and Center for Atomic-Scale Materials Physics, DK-8000 Aarhus C, Denmark. E. W. Plummer, Department of Physics and Astronomy, University of Tennessee, Knoxville, TN 37996, USA, and Solid State Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.
Petersen
L
Plummer
EW
Laegsgaard
E
Besenbacher
F