Regensburg 2010 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 33: TR: Nanoelectronics I: Quantum Dots, Wires, Point Contacts 2

TT 33.5: Talk

Thursday, March 25, 2010, 15:00–15:15, H19

Quantum Ratchets Driven by Tunnel Oscillations — •Sigmund Kohler and Michael Stark — Instituto de Ciencia de Materiales de Madrid, CSIC, Cantoblanco, 28049 Madrid, Spain

The ratchet effect, which is the induction of a dc current by an ac force in the absence of any net bias, represents one of the most intriguing phenomena in non-equilibrium transport. In the usual description, it is assumed that the ratchet is driven by a classical field, while the corresponding backaction can be ignored. Here we address the question whether the tunnel oscillations of a biased double quantum dot can be employed as driving source. Since such a driving source itself behaves quantum mechanically, its dynamics will be influenced by the ratchet and, thus, should be treated as a further degree of freedom. As a model, we use two capacitively coupled double quantum dots: a biased one that provides the ac force and an asymmetric, unbiased one that acts as ratchet in the predominantly coherent quantum regime. It turns out that the two-electron states of the coupled drive-pump Hamiltonian leave their fingerprints in the ratchet current.