Andreev reflection through a quantum dot coupled with two ferromagnets and a superconductor
Abstract
We study the Andreev reflection (AR) in a three terminal mesoscopic hybrid system, in which two ferromagnets (F1 and F2) are coupled to a superconductor (S) through a quantum dot (QD). By using non-equilibrium Green function, we derive a general current formula which allows arbitrary spin polarizations, magnetization orientations and bias voltages in F1 and F2. The formula is applied to study both zero bias conductance and finite bias current. The current conducted by crossed AR involving F1, F2 and S is particularly unusual, in which an electron with spin σ incident from one of the ferromagnets picks up another electron with spin σ from the other one, both enter S and form a Cooper pair. Several special cases are investigated to reveal the properties of AR in this system.
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