Cotunneling spectroscopy of coupled spin systems – Niels Bohr Institute - University of Copenhagen

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Niels Bohr Institute > Calendar > 2012 > Cotunneling spectrosco...

Cotunneling spectroscopy of coupled spin systems

Over the past few years, experiments on three-terminal molecular junctions gave new insights in the understanding of a variety of quantum electron transport effects. In this work, we model a molecular junction in the Coulomb Blockade regime as a few-electron system tunnel coupled to two electrodes. We calculate the differential conductance due to cotunneling and study the behavior of the Kondo temperature of the system, which in general depends on the internal exchange couplings between the interacting electron spins. Moreover we demonstrate that a simple two-electron model allows to reproduce a peculiar, not previously explained, feature characterizing the differential conductance of a Mn complex in the neighborhood of a singlet to triplet ground-state transition. We come to the conclusion that such a feature must be due to the non-equilibrium rearrangement of the occupation probability of the different two-electron states.

Supervisor: Assoc. Prof. Jens Paaske
Censor: Assoc. Prof. Mads Brandbyge

Thesis defense by Chiara Stevanato