Regensburg 2016 – scientific programme
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O: Fachverband Oberflächenphysik
O 13: Magnetic Surface Excitations
O 13.3: Talk
Monday, March 7, 2016, 15:45–16:00, S052
Tuning the Kondo coupling strength of a single molecule — •Olof Peters1, Benjamin W. Heinrich1, Christian Lotze1, Xianwen Chen1, Markus Ternes2, and Katharina J. Franke1 — 1Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany — 2Max-Planck Institut for Solid State Research, Stuttgart, Germany
Metal adatoms on a metal surface are typically strongly Kondo coupled, leading to a high Kondo temperature TK, whereas insulating films efficiently reduce the coupling of such adsorbates resulting in much lower TK. This decoupling gives the opportunity to study the Kondo effect with today’s accessible magnetic fields and temperature ranges. A disadvantage of these isolating layers is the fixed coupling constant determined by the specific system.
We report on the controllable, continuous and reversible tuning of the Kondo coupling between a metal-organic complex (Fe-octaethylporphyrin-Cl) and its underlying Au(111) metal surface under the influence of a scanning tunnelling microscope tip at 1.1 K. Upon approach of the STM tip to the Fe core, the magnetic anisotropy increases and eventually a Kondo resonance appears. The Kondo coupling strength continuously increases at further tip approach.
We ascribe these results to a modification of the crystal field by the tip leading to a shift in the d-level energies. The change in crystal field also results in a relaxation of the Fe atom towards the substrate thus tuning the magnetic interactions from weak into the strong Kondo coupling regime.