AVS 50th International Symposium
    Magnetic Interfaces and Nanostructures Tuesday Sessions
       Session MI+NS-TuM

Invited Paper MI+NS-TuM4
Scanning Tunneling Spectroscopy of Magnetic Impurities at Metal Surfaces

Tuesday, November 4, 2003, 9:20 am, Room 316

Session: Magnetic Imaging and Magnetic Spectroscopies
Presenter: M.A. Schneider, Max Planck Institute for Solid State Research, Germany
Correspondent: Click to Email
A single magnetic impurity in a metal host is a paradigm of many-body physics in electronic systems. The spin-flip scattering of host electrons at the impurity site leads to the formation of a correlated electron state, the Kondo state. Only recently has it become possible to study this state using Scanning Tunneling Spectroscopy (STS) for magnetic surface impurities.@footnote 1-5@ Through this method, magnetism and properties of the adsorbate-host interaction can be determined in a local, atomic-scale measurement. The Kondo state is characterized by the formation of a resonance at the Fermi energy, which allows to access the characteristic energy scale, the Kondo temperature T@sub K@ of the system. We discuss the properties of the Kondo state created by the interaction of the magnetic atom with surface and bulk electrons, and the role of the tunneling process in the appearance of the resonance in STS spectra. The interaction of the magnetic impurity with two-dimensional surface-state electrons is demonstrated by the measurement of a resonant scattering phase-shift for Co adsorbed on Ag(111).@footnote 4@ However, this interaction with surface-state electrons is only weak, the main properties of the Kondo state are determined by the interaction with bulk electrons. This is corroborated by experiments comparing Co impurities on various Cu surfaces where the decisive role of the number of interaction channels to bulk electrons in the atomic-scale system is shown.@footnote 5@. @FootnoteText@ @footnote 1@ J.-T. Li, W.-D. Schneider, R. Berndt, B. Delley, Phys. Rev. Lett. 80, 2893(1998)@footnote 2@ V. Madhavan, W. Chen, T. Jamneala, M. F. Crommie, N. S. Wingreen, Science 280, 567 (1998) @footnote 3@ H.C. Manoharan, C. Lutz, D. M. Eigler, Nature 403, 512 (2000)@footnote 4@ M. A. Schneider, L. Vitali, N. Knorr, K. Kern, Phys. Rev. B 65, 121406(R) (2002)@footnote 5@ N. Knorr, M. A. Schneider, L. Diekhöner, P. Wahl, K. Kern, Phys. Rev. Lett. 88, 096804 (2002).