Spin Current and Current-Induced Spin Transfer Torque in Ferromagnet-Quantum Dot-Ferromagnet Coupled Systems

摘要

Based on Keldysh's nonequilibrium Green function method, the spin-dependenttransport properties in a ferromagnet-quantum dot (QD)-ferromagnet coupledsystem are investigated. It is shown the spin current shows quite differentcharacteristics from its electrical counterpart, and by changing the relativeorientation of both magnetizations, it can change its magnitude even sign. Thecurrent-induced spin transfer torque (CISTT) is uncovered to be greatlyenhanced when the bias voltage meets with the discrete levels of the QD atresonant positions. The relationship between the CISTT, the electrical currentand the spin current is also addressed.