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Wegewijs group - Single molecule quantum transport

Please visit also the corresponding Theoretical Nanoelectronics (PGI-2) page at Research Center Jülich.

Recent highlights


Spintronic magnetic anisotropy
Besides the dissipative injection of spin-anisotropy (similar to the spin-accumulation), we now also theoretically established its coherent counterpart (similar to the spin-torque). This completes the picture of transport of spin-quadrupole moment, the first corrections beyond transport of charge and spin. We showed that quantum dots with a spin > 1/2, when connected to ferromagnets, are subject to a quadrupolar exchange field, in addition to the well-established dipolar exchange field of Martinek and König. In the Coulomb blockade regime such a quantum dot is exactly equivalent to a single-molecule magnet. However, no spin-orbit coupling is required and the effective magnetic field and anisotropy are electrically tuneable and swicheable by the relative polarizations of the spin-valve.
Nature Physics, Published online 6 October 2013; DOI: 10.1038/nphys2766
Press Release

Spin-multipoletronics: why spin-currents are not enough for spintronics.
We found that for quantum dots with spin S > 1/2 embedded in circuits with ferromagnets new types of physical currents must be accounted for. These spin-multipole currents describe the non-equilibrium transport of the anisotropy of spin. This establishes an important new link between the research fields of molecular magnetism (where spin-anisotropy is intrinsically present molecules) and spintronics (where spin-properties are injected from external sources). Spin anisotropy can thus be generated and controlled electrically!
Phys. Rev. Lett. 107, 087202 (2011)

Enhanced Coulomb blockade spectroscopy by adiabatic driving
By adding adiabatically driven, out-of-phase gate and bias potentials to a standard 3-terminal transport measurements additional detailed information can be extracted from the time-averaged current through a quantum dot. An extra current arises solely due to a breaking of the symmetry in time of charging and discharging processes by strong Coulomb interactions (i.e. beyond the mean-field level). Interestingly, this new adiabatic Coulomb blockade spectroscopy allows spin-degeneracies to be detected without a magnetic field!
Phys. Rev. Lett. 104, 226803 (2010)

Projects

The group is funded by the Helmholtz Association (HGF), in particular by the Inititiative and Networking Fund, with the aim of building a cooperation between the RWTH Aachen and the Research Center Jülich in the field molecular electronics. It is based at the Theoretical Nanoelectronics Division of the Peter Grünberg Institute (PGI-2) for Nanoelectronics at the Research Center Jülich (Forschungszentrum Jülich) and is co-hosted by Institute for Theory of Statistical Physics at the RWTH Aachen. It is furthermore affiliated with the Institute for Quantum Information at the RWTH Aachen.

Press

Kondo effect in single magnetic molecules - article on www.physorg.com

Former Group Members

Dr. Christian Romeike D-fine Consulting
Dr. Katja Nowack Moler Group, Stanford University, US
Dipl.-Phys. Stefan Herzog STS GmbH
Dr. Martin Leijnse Lund University, Sweden
Dipl.-Phys. Markus Kurz Institute for Laserphysics, Hamburg
Ms.-Sc. Julian Bohle DFS Deutsche Flugsicherung GmbH
Dr. Hernan L. Calvo, Postdoc fellow at National Scientific and Technical Research Council (CONICET), Argentina

Abschlußinformationen