Regensburg 2010 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 3: TR: Fluctuations and Noise

TT 3.2: Talk

Monday, March 22, 2010, 10:30–10:45, H20

Spin-induced charge correlations in transport through interacting quantum dots with ferromagnetic leads — •Stephan Lindebaum, Daniel Urban und Jürgen König — Theoretische Physik, Universität Duisburg-Essen and CeNIDE, 47048 Duisburg, Germany

We study the full counting statistics of electronic transport through a single-level quantum dot weakly coupled to two leads, with either one or both of them being ferromagnetic[1]. Starting from a generalized master equation we use a diagrammatic real-time theory to calculate the cumulant generating function to first order in the tunnel-coupling strength. In both considered systems, we find that the interplay of Coulomb interaction and finite spin polarization implies spin-correlation induced charge correlations that give rise to super-Poissonian transport behavior. In the case of two ferromagnetic leads, we analyze the non-trivial dependence of the cumulants on the angle between the non-collinear polarization directions of the leads. We find even diverging second and higher cumulants for spin polarizations approaching unity. But already the system with one ferromagnetic and one normal lead displays super-Poissonian behavior and, in addition, positive cross correlations between the current fluctuations of the two spin species, if the electrons are injected from the normal electrode.

[1] S. Lindebaum, D. Urban, and J. König, Phys. Rev. B 79, 245303 (2009).