Superconducting proximity effect and zero-bias anomaly in transport through quantum dots weakly attached to ferromagnetic leads

Ireneusz Weymann; Piotr Trocha

doi:10.1103/PhysRevB.89.115305

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Superconducting proximity effect and zero-bias anomaly in transport through quantum dots weakly attached to ferromagnetic leads

Ireneusz Weymann, Piotr Trocha

DOI 10.1103/PhysRevB.89.115305 · Physical Review B

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Abstract

The Andreev transport through a quantum dot coupled to two external ferromagnetic leads and one superconducting lead is studied theoretically by means of the real-time diagrammatic technique in sequential and cotunneling regimes. We show that the tunnel magnetoresistance (TMR) of the Andreev current displays a nontrivial dependence on the bias voltage and the level detuning and can be described by analytical formulas in the zero-temperature limit. The cotunneling processes lead to a strong modification of the TMR, which is most visible in the Coulomb blockade regime. We find a zero-bias anomaly of the Andreev differential conductance in the parallel configuration, which is associated with a nonequilibrium spin accumulation in the dot triggered by Andreev processes.