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TT: Fachverband Tiefe Temperaturen

TT 37: Transport: Nanoelectronics II - Spintronics and Magnetotransport

TT 37.3: Vortrag

Donnerstag, 26. März 2009, 10:00–10:15, HSZ 105

Transport through an interacting quantum dot tunnel coupled to a ferromagnet with time-dependent magnetisation — •Nina Winkler, Michele Governale, and Jürgen König — Theoretische Physik · Universität Duisburg-Essen

We study adiabatic pumping through a system consisting of a quantum dot coupled to a normal and a ferromagnetic lead. Adiabatic pumping is typically studied in systems in which the properties of the scattering region are changed, e.g. gate voltages to vary the tunnel couplings and the level position of the quantum dot. Here, we consider a different pumping scheme. By changing slowly in time the lead properties, e.g. the magnetisation, we can generate a pumped DC current. To this aim, we generalise a diagrammatic real-time approach for adiabatic pumping through quantum dots with ferromagnetic leads [ 1, 2] to account for a time-dependent magnetisation.

We consider two different pumping situations: First, we choose the amplitude of the magnetisation of the ferromagnetic lead and the level position of the dot or the tunnel coupling to the normal lead as pumping parameters. Second, we pump by periodically changing the direction of the magnetisation. We investigate the adiabatic charge and spin transport through the system by performing a systematic perturbative expansion in powers of the tunnel-coupling strengths but treating the on-site Coulomb interaction on the quantum dot exactly.
[ 1] J. Splettstoesser et al. , Phys. Rev. B 74, 085305 (2006).
[ 2] J. Splettstoesser et al. , Phys. Rev. B 77, 195320 (2008).