"Andreev current enhancement and subgap conductance of superconducting hybrid
structures in the presence of a small spin-splitting field"
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We investigate the subgap transport properties of a S-F-N structure. Here S (N)
is a superconducting (normal) electrode, and F is either a ferromagnet or a
normal wire in the presence of an exchange or a spin-splitting Zeeman field
respectively. By solving the quasiclassical equations we first analyze the
behavior of the subgap current, known as the Andreev current, as a function of
the field strength for different values of the voltage, temperature and length
of the junction. We show that there is a critical value of the bias voltage
above which the Andreev current is enhanced by the spin-splitting field. This
unexpected behavior can be explained as the competition between two-particle
tunneling processes and decoherence mechanisms originated from the temperature,
voltage and exchange field respectively. We also show that at finite temperature
the Andreev current has a peak for values of the exchange field close to the
superconducting gap. Finally, we compute the differential conductance and show
that its measurement can be used as an accurate way of determining the strength
of spin-splitting fields smaller than the superconducting gap.
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References:
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[1] A. Ozaeta, A. S. Vasenko, F. W. J. Hekking, F. S. Bergeret, arXiv:1203.3679
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[2] A. Ozaeta, A. S. Vasenko, F. W. J. Hekking, F. S. Bergeret, to appear this week in arXiv