Regensburg 2016 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 16: Transport: Quantum Dots, Quantum Wires, Point Contacts

TT 16.3: Vortrag

Montag, 7. März 2016, 15:30–15:45, H21

Current cross-correlations in double quantum dot Cooper pair splitter. — •Kacper Wrześniewski, Piotr Trocha, and Ireneusz Weymann — Faculty of Physics, Adam Mickiewicz University, 61-614 Poznań, Poland

We investigate theoretically transport properties of a quantum dot (QD) system working as a Cooper pair splitter.[1] The device is coupled to one superconducting and two ferromagnetic leads. Presented results are calculated using real-time diagrammatic technique in the sequential tunneling approximation with respect to the coupling to ferromagnetic leads. The transport properties are evaluated within the superconductor subgap regime taking into account Andreev reflection processes solely.[2]

We focus on the analysis of current and current cross-correlations, both in linear and nonlinear responses. Current cross-correlations give additional information about dynamics of transport processes. We identify both positive and negative signs of current cross-correlations and discuss mechanisms leading to those results. Strong negative cross-correlations are found when the occupation number of QD system becomes degenerate and near the emergence of the triplet blockade, while positive ones occur in the most range where current flows due to crossed Andreev processes. Finally, we consider ferromagnetic leads polarization and temperature influences on aforementioned features.
L. Hofstetter, S. Csonka, J. Nygård, and C. Schönenberger,

Nature 461, 960 (2009).
P. Trocha and I. Weymann, PRB 91, 235424 (2015).