Aharonov-Bohm oscillations and spin-polarized transport in a mesoscopic ring with a magnetic impurity

We present a detailed analysis of Aharonov-Bohm (AB) interference oscillations manifested through transmission of an electron in a mesoscopic ring with a magnetic impurity atom inserted in one of its arms. Spin-polarized transport is also studied. The electron interacts with the impurity through exchange interaction, leading to spin-flip scattering. Transmission in the spin-flipped and -unflipped channels are explicitly calculated. We show that entanglement between electron and spin-flipper states leads to reduction of AB oscillations in spite of the absence of any inelastic scattering. The spin conductance (related to spin-polarized transmission coefficient) is asymmetric under flux reversal, as opposed to the two-probe conductance, which is symmetric. We point out certain limitations of this model in regard to the general notion of dephasing in quantum mechanics.