Regensburg 2007 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 18: Nanoelectronics I - Quantum Dots, Wires, Point Contacts
TT 18.4: Vortrag
Mittwoch, 28. März 2007, 14:45–15:00, H19
Generation of Nonlocal Spin Entanglement in Nonequilibrium Quantum Dots — •Stefan Legel1, Jürgen König2, Guido Burkard3, and Gerd Schön1 — 1Institut für Theoretische Festkörperphysik and DFG-Center for Functional Nanostructures (CFN), Universität Karlsruhe — 2Institut für Theoretische Physik III, Ruhr-Universität Bochum — 3Department of Physics and Astronomy, University of Basel
We propose schemes for generating nonlocal spin entanglement in systems of two quantum dots with onsite Coulomb repulsion weakly coupled to a joint electron reservoir. In nonequilibrium situations with one extra electron on each dot, we find the double-dot system in so-called Werner states with a fidelity exceeding 1/2, which indicates spin entanglement. We consider two specific setups. In the first setup we study the transient behavior of the system after rapidly pushing the dot levels from above to below the Fermi energy of the joint lead. We find the formation of an enhanced probability of the singlet state as compared to the triplet. In the second setup we analyze the stationary state with an applied bias voltage between the joint reservoir and two additional leads, which are weakly coupled to the dots. Depending on the polarity of the bias, we find an enhanced probability for either the singlet or the triplet states.