Phys. Rev. B 76, 125318 (2007) [7 pages]Transient charging and discharging of spin-polarized electrons in a quantum dotReceived 27 April 2007; published 21 September 2007 We study spin-polarized transient transport in a quantum dot coupled to two ferromagnetic leads subjected to a rectangular bias voltage pulse. Time-dependent spin-resolved currents, occupations, spin accumulation, and tunneling magnetoresistance (TMR) are calculated using both nonequilibrium Green function and master equation techniques. Both parallel- and antiparallel-lead magnetization alignments are analyzed. Our main findings are a dynamical spin accumulation that changes sign in time, a short-lived pulse of spin polarized current in the emitter lead (but not in the collector lead), and a dynamical TMR that develops negative values in the transient regime. We also observe that the intradot Coulomb interaction can enhance even further the negative values of the TMR. © 2007 The American Physical Society URL:
http://link.aps.org/doi/10.1103/PhysRevB.76.125318
DOI:
10.1103/PhysRevB.76.125318
PACS:
72.25.−b, 73.23.−b, 73.63.Kv, 72.10.Bg
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