AVS 56th International Symposium & Exhibition
    Magnetic Interfaces and Nanostructures Friday Sessions
       Session MI-FrM

Paper MI-FrM6
Spatially Extended Kondo Resonance in Magnetic Molecules

Friday, November 13, 2009, 10:00 am, Room C1

Session: Molecular/Organic Based Magnetism
Presenter: S.E. Ulloa, Ohio University
Authors: U.G.E. Perera, Ohio University
H.J. Kulik, Massachusetts Institute of Technology
V. Iancu, Ohio University
L.G.G.V. Dias da Silva, Oak Ridge National Laboratory and University of Tennessee
S.E. Ulloa, Ohio University
N. Marzari, Massachusetts Institute of Technology
S.-W. Hla, Ohio University
Correspondent: Click to Email
Molecules containing transition-metal complexes have great potentials in the emergent fields of spintronics and molecular electronics. Especially, controlling their spin states and spin polarization is a key challenge for future applications. Here, we report an extensive and unusual redistribution of spin density for self-assembled TBrPP-Co [5, 10, 15, 20 –Tetrakis -(4-bromophenyl)-porphyrin-cobalt] molecules adsorbed on a Cu(111) surface as a model system to investigate spin polarization, the effect of molecular orbital in Kondo resonances. The TBrPP-Co molecule has a spin-active cobalt atom caged at the center of porphyrin unit and four bromo-phenyl groups are attached to its four corners. STM imaging shows the molecules with four pronounced lobes. These molecules readily self-assemble and form ordered, ribbon-like monolayer islands on Cu(111), with a preferential growth direction ~7º deviated from the [110] surface directions. We probe the spatially extended Kondo resonance of the molecules by monitoring the effective Kondo temperature with differential conductance (dI/dV) tunneling spectroscopy, finding it much larger on the macro-cycle itself than on the central cobalt atom. The origin of this effect is explained by means of first-principles and numerical renormalization group calculations, highlighting how it is possible to engineer spin polarization and electronic transport by means of adsorption chemistry. This work is supported by the US Department of Energy Basic Energy Sciences grant no. DE-FG02-02ER46012.