Photon-assisted tunneling in a hybrid junction based on a quantum dot coupled to two ferromagnets and a superconductor

Photon-assisted transmission (PAT) through a three-terminal hybrid system based on a quantum dot coupled to two ferromagnetic (F) and one superconducting (S) electrodes is studied in the sub-gap regime. Linear conductance is calculated within the non-equilibrium Green function technique. The effect of PAT on the local and non-local conductances for arbitrary angles between the magnetic moments of the F electrodes is studied. A generalized formula for the Andreev reflection magnetoresistance (ARMR) is proposed and it is found that the linear conductance may be significantly modified by the photon-assisted tunneling, while ARMR remains practically unaffected by PAT. Also, the conditions for the ARMR inversion have been determined for an interplay between the transport processes occurring in the system, magnetic polarization of the F leads and the angular configuration of the magnetic moments in the F leads. It has been shown that by manipulating the a.c. amplitude and the photon angular frequency one may control the contributions to the total conductance originating from Andreev reflection, crossed Andreev reflection as well as electron tunneling between the F leads. The influence of the non-vanishing intradot Coulomb correlations on PAT in the considered three-terminal hybrid system is also discussed. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)