Kondo effect in charge transfer complexes
Final Report Abstract
The goal of the project was a fundamental understanding of charge transfer processes and the related Kondo effect on metal surfaces. Employing low-temperature scanning tunneling microscopy and spectroscopy, we investigated self-assembled monolayers of different charge transfer systems. We showed that the charge state is not only determined by the electron affinity and the ionization potential of the constituents, but also crucially depends on the atomic-scale details of the adsorption configuration. Particularly interesting are systems in which the charge state can be controlled by the electric field in the tunneling junction. This resembles the situation of a gate electrode in three-terminal devices. In other systems, we found that instabilities in the adsorption configuration can be switched by a combination of tunneling electrons and electric field. Furthermore, we created highly ordered networks consisting of transition metal atoms and organic linkers. The structure of these networks was determined by scanning tunneling microscopy. In combination with x-ray circular magnetic dichroism measurements, we could identify a magnetically coupled ground state, where the spin interaction probably proceeds via the organic linker. Further experiments are planned to investigate the tunability of the interaction strength and the competition of possible coupling mechanisms. These experiments were carried out in cooperation with group of Wolfgang Kuch from Freie Universität Berlin.
Publications
- Enhanced charge transfer in a monolayer of the organic charge transfer complex TTF- TNAP on Au(111), Journal of Physics: Condensed Matter, 24, 354003 (2012)
T. R. Umbach, I. Fernandez-Torrente, J. N. Ladenthin, J.I. Pascual, K. J. Franke
(See online at https://doi.org/10.1088/0953-8984/24/35/354003) - Ferromagnetic coupling of mononuclear Fe centers in a self-assembled metal organic network on Au(111), Physical Review Letters, 109, 267207 (2012)
T. R. Umbach, M. Bernien, C. F. Hermanns, A. Krüger, I. Fernández-Torrente, P. Stoll, J. I. Pascual, K. J. Franke, and W. Kuch
(See online at https://doi.org/10.1103/PhysRevLett.109.267207) - Gating the charge state of a single molecule by local electric fields, Physical Review Letters 108, 036801 (2012)
I. Fernandez-Torrente, D. Kreikemeyer-Lorenzo, A. Strozecka, K. J. Franke, J.I. Pascual
(See online at https://doi.org/10.1103/PhysRevLett.108.036801) - Atypical charge distribution over a charge-transfer monolayer on a metal, New Journal of Physics, 15, 083048 (2013)
T. R. Umbach, I. Fernandez-Torrente, M. Ruby, F. Schulz, C. Lotze, R. Rurali, M. Persson, J. I. Pascual, K. J. Franke
(See online at https://doi.org/10.1088/1367-2630/15/8/083048) - Charged and Metallic Molecular Monolayers through Surface-Induced Aromatic Stabilisation, Nature Chemistry, 5, 187 (2013)
G. Heimel, S. Duhm, I. Salzmann, A. Gerlach, A. Strozecka, J. Niederhausen, C. Bürker, T. Hosokai, I. Fernandez-Torrente, G. Schulze, S. Winkler, A. Wilke, R. Schlesinger, J. Frisch, B. Bröker, A. Vollmer, B. Detlefs, J. Pflaum, S. Kera, K. J. Franke, N. Ueno, J. I. Pascual, F. Schreiber, N. Koch
(See online at https://doi.org/10.1038/NCHEM.1572) - Orbital Redistribution in Molecular Nanostructures Mediated by Metal-Organic Bonds, ACS Nano, 8, 10715 (2014)
Zechao Yang, Martina Corso, Roberto Robles, Christian Lotze, Roland Fitzner, Elena Mena-Osteritz, Peter Bäuerle, Katharina J. Franke, and Jose I. Pascual
(See online at https://doi.org/10.1021/nn504431e) - Site-specific bonding of copper adatoms to pyridine end groups mediating the formation of two-dimensional coordination networks on metal surfaces, Physical Review B, 89, 235409 (2014)
T. R. Umbach, M. Bernien, C. F. Hermanns, L. L. Sun, H. Mohrmann, K. E. Hermann, A. Krüger, N. Krane, Z. Yang , F. Nickel, Y.-M. Chang, K. J. Franke, J. I. Pascual, W. Kuch
(See online at https://doi.org/10.1103/PhysRevB.89.235409)
