IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Magnetic Interfaces and Nanostructures Friday Sessions
       Session MI+SS-FrM

Paper MI+SS-FrM6
Direct Observation of Orbital Kondo Resonance on the Cr(001) Surface

Friday, November 2, 2001, 10:00 am, Room 110

Session: Magnetic Thin Films and Surfaces II
Presenter: H. van Kempen, University of Nijmegen, The Netherlands
Authors: O.Yu. Kolesnychenko, University of Nijmegen, The Netherlands
R. de Kort, University of Nijmegen, The Netherlands
M.I. Katsnelson, University of Nijmegen, The Netherlands
A.I. Lichtenstein, University of Nijmegen, The Netherlands
H. van Kempen, University of Nijmegen, The Netherlands
Correspondent: Click to Email
Scanning Tunneling Microscopy (STM) is an excellent tool to explore many-body phenomena, such as the formation of the Kondo resonance@footnote 1@. In addition to``classical'' Kondo effect, many-electron resonances have been theoretically predicted for scattering centers with non-spin degrees of freedom. Here, we will present the first direct evidences for the existence of orbital Kondo resonance on a transition metal surface. Low-Temperature STM and STS investigations were performed on the atomically clean Cr(001). The Cr(001) surface was produced by cleavage of a 99.99% Cr single crystal in situ at 4K. As we found out, the cleavage of Cr single crystals produce atomically flat and clean (001) surfaces. The STS investigations of the Cr(001) surfaces showed a very narrow resonance at 26 meV above the Fermi level. We found that at bias voltages corresponding to the resonance energy a cross-like depressions centered around impurities appears. This cross-like feature is a fingerprint of the orbital symmetry of the resonance analogous, for example, to the visualization of a superconducting gap near a zinc atom@footnote 2@. Although the resonance in the Cr(001) surface density of states has been observed previously at room temperature@footnote 3@ and was interpreted as a one-electron surface state, we are going to present additional experimental data which strongly indicate that the observed state on the Cr(001) surface is a many-electron orbital Kondo resonance which is formed by two degenerate spin-split d@sub xz@, d@sub yz@ surface states. We also carried out calculations for the periodic degenerated Anderson model which confirm the existence of the orbital Kondo resonance on the Cr(001) surface. @FootnoteText@ @footnote 1@ H.C. Madhaven, et.al., Nature 403, 512 (2000). @footnote 2@ S.H. Pan. et.al., Nature 403, 746 (2000). @footnote 3@ J.A. Stroscio, et.al., Phys. Rev. Lett. 75, 2960 (1996).