Berlin 2005 – scientific programme
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TT: Tiefe Temperaturen
TT 19: Transport - Nanoelectronics I: Spintronics and Magnetotransport
TT 19.3: Talk
Monday, March 7, 2005, 10:30–10:45, TU H3027
Zero-bias anomaly in cotunneling transport through quantum-dot spin valves — •Jürgen König3, Ireneusz Weymann1, Józef Barnaś1,2, Jan Martinek2,4, and Gerd Schön4 — 1Department of Physics, Adam Mickiewicz University, 61-614 Poznań, Poland — 2Institute of Molecular Physics, Polish Academy of Sciences, 60-179 Poznań, Poland — 3Institut für Theoretische Physik III, Ruhr-Universität Bochum, 44780 Bochum, Germany — 4Institut für Theoretische Festkörperphysik, Universität Karlsruhe, 76128 Karlsruhe, Germany
Quantum dots attached to ferromagnetic leads define quantum-dot spin valves. The interplay of spin-dependent transport due to finite spin polarization in the leads and strong Coulomb interaction gives rise to complex transport behavior. In the limit of weak dot-lead coupling, and deep in the Coulomb-blockade regime, sequential tunneling [1,2] is suppressed, and transport is dominated by cotunneling [3].
We analyze cotunneling transport through a quantum-dot spin valve with antiparallel alignment of the leads’ magnetic moments. We find a zero-bias anomaly in the differential conductance for Coulomb-blockade valleys with an unpaired dot electron. It is a consequence of the interplay of single- and double-barrier cotunneling processes and their effect on the spin accumulation in the dot. The anomaly becomes significantly modified when an external magnetic field is applied.
[1] J. König and J. Martinek, Phys. Rev. Lett. 90, 166602 (2003).
[2] M. Braun, J. König, and J. Martinek, cond-mat/0404455.
[3] I. Weymann, J. Barnaś, J. König, J. Martinek, and G. Schön, preprint.