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TT: Fachverband Tiefe Temperaturen

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

TT 33.1: Vortrag

Donnerstag, 25. März 2010, 14:00–14:15, H19

Negative tunneling magneto-resistance in spin-polarized transport across carbon nanotubes — •Sonja Koller¹, Jens Paaske², and Milena Grifoni¹ — ¹Universität Regensburg — ²Nano-Science Center, University of Copenhagen

From experiments on carbon nanotube single electron transistors with ferromagnetic, collinearly polarized leads, it is known that the tunneling magneto-resistance (a measure for the ratio of current in the parallel to current in the anti-parallel contact configuration) exhibits a strong dependence on the gate voltage. In particular, for certain gate regions, the anti-parallel current can even exeed the parallel one, leading to negative values of the tunneling magneto-resistance. The origin of this effect are tunneling induced level shifts, that we are able to calculate theoretically within a diagrammatic perturbation approach to transport across quantum dots, by inclusion and summation of certain diagram types to all orders. A qualitative agreement with the experiment is obtained.