Dresden 2009 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 46: Correlated Electrons: Quantum Impurities, Kondo Physics
TT 46.1: Vortrag
Freitag, 27. März 2009, 10:15–10:30, HSZ 301
Spatial Variation of Fano Resonances in the STM Tunneling Density of States due to Sub-Surface Kondo Impurities — •Henning Prüser, Martin Wenderoth, Alexander Weismann, and Rainer G. Ulbrich — IV. Physikalisches Institut; Georg-August Universität Göttingen, Germany
Single magnetic atoms buried in copper have been investigated using low temperature scanning tunneling spectroscopy (STS). Cu alloys with a small amount (≤ 0.02%) of iron and cobalt were epitaxially grown on a Cu(100) substrate. The embedded Fe and Co impurities were identified in STM topographies at 6K by their fourfold symmetric topography patterns. From comparison with scattering theory in anisotropic media we obtain their individual depths, ranging from 3 to 9 ML. In the STS data both Fe and Co show the expected Kondo feature: a Fano resonance centered at EF, and a width directly related to the Kondo temperature TK. Our TK values for Fe and Co corroborate parameters deduced from bulk measurements. The line shape of the LDOS spectrum around EF depends strongly on (i) the lateral distance of the tip from the impurity and (ii) the impurity depth below the surface. As a function of these two lengths the line shape shows an oscillatory behavior. The path length period equals the Friedel wave length of copper as predicted by theory [1, 2]. Work supported by DFG SFB 602 TPA3.
[1] Újsághy et al., PRL 82, 2557, 2000
[2] Plihal et al., PRB 63, 085404, 2001