Spin-polarized current and shot noise in the presence of spin flip in a quantum dot via nonequilibrium Green's functions

Abstract

Using non-equilibrium Green functions we calculate the spin-polarized current and shot noise in a ferromagnet--quantum-dot--ferromagnet (FM-QD-FM) system. Both parallel (P) and antiparallel (AP) magnetic configurations are considered. Coulomb interaction and coherent spin-flip (similar to a transverse magnetic field) are taken into account within the dot. We find that the interplay between Coulomb interaction and spin accumulation in the dot can result in a bias-dependent current polarization $\wp$. In particular, $\wp$ can be suppressed in the P alignment and enhanced in the AP case depending on the bias voltage. The coherent spin-flip can also result in a switch of the current polarization from the emitter to the collector lead. Interestingly, for a particular set of parameters it is possible to have a polarized current in the collector and an unpolarized current in the emitter lead. We also found a suppression of the Fano factor to values well below 0.5.

Published version. 13 pages, 7 figures

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• What can we learn about the dynamics of transported spins by measuring shot noise in spin-orbit-coupled nanostructures?
• Spin current and polarization reversal through a single-molecule magnet with ferromagnetic electrodes
• Superpoissonian shot noise in organic magnetic tunnel junctions
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• Influence of spin-flip on the performance of the spin-diode