Coulomb Promotion of Spin-Dependent Tunneling

Abstract

We study transport of spin-polarized electrons through a magnetic single-electron transistor (SET) in the presence of an external magnetic field. Assuming the SET to have a nanometer size central island with a single-electron level we find that the interplay on the island between coherent spin-flip dynamics and Coulomb interactions can make the Coulomb correlations promote rather than suppress the current through the device. We find the criteria for this new phenomenon--Coulomb promotion of spin-dependent tunneling--to occur.

Electronic spin working mechanically (Review Article)

“…One of the remarkable consequences is the Coulomb promotion of spin-dependent tunneling predicted in Ref. 47. In this work a strong voltage dependence of the spin-flip relaxation rate on a quantum dot was demonstrated.…”

“…It was shown in Ref. 47 that by lifting the Coulomb blockade one stimulates occupation of both spin-up and spin-down states thus suppressing spinflip relaxation on the dot. In magnetic devices with highly spin-polarized electrons electronic spin-flip can be the only mechanism providing charge transport between oppositely magnetized leads.…”

“…41. This principle may lead to a giant magnetoresistance effect in external magnetic fields as low as 1-10 Oe in a magnetic shuttle device if magnets with highly spin-polarized electrons (half metals [42][43][44][45][46]) are used as leads in a magnetic shuttle device.…”

“…The theory [41] predicts oscillations in the magnetoresistance of the magnetic shuttle device with a period ∆H p , which is determined from the equationhω 0 = gµ(1 + w)∆H p . The physical meaning of this relation is simple: every time when ω 0 /Ω = n + 1/2 (Ω = gµH/h is the spin precession frequency in a magnetic field) the shuttled electron is able to flip fully its spin to remove the "spin-blockade" of tunneling between spin polarized leads having their magnetization in opposite directions.…”

“…The model employed in Ref. 41 assumes that the source and drain are fully polarized in opposite directions. A mechanically movable quantum dot (described by a time-dependent displacement x(t)), where a single energy level is available for electrons, performs driven harmonic oscillations between the leads.…”