Transient Magnetic Tunneling Mediated by a Molecular Bridge
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This paper extends our recent theoretical study Kalvová et al. (J. Supercon. and Novel Mag. 26, 773 2013) of transient currents through molecular bridges to magnetic tunneling. We calculate the excess magnetization on a molecular bridge shunting the magnetic junction. The system is represented by two ferromagnetic electrodes bridged by a molecular size island with a few discrete electronic levels and a local Hubbard type correlation. The island is linked to the electrodes by tunneling junctions. One of the junctions is permanent, the coupling strength of the other one is assumed to undergo rapid changes modulating the connectivity of the system. The sudden switching events give rise to transient magnetic currents resulting in changes of magnetization at the island. They vary with the constant galvanic bias between the electrodes. Depending on the time scale of the switching series, the transients are dominated by the initial quantum correlations, or reach the kinetic stage controlled by a simple relaxation mechanism. We employ the nonequilibrium Green’s functions. The finite-time correlated initial conditions are taken into account using the partitioning-in-time method we developed previously Velický et al. (Phys. Rev. B 81, 235116 2010). The numerical solution is obtained solving the real-time Dy-son equation in the integro-differential form self-consistently. For long time asymptotic, a generalized master equation is matched to the initial stage solution.
KeywordsNon-equilibrium Initial conditions Transient currents Molecular islands
The authors acknowledge financial support from the Czech Science Foundation (P204/12/0897).