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Charge Transport and Quantum Phase Transitions in Singlet Superconductor - Ferromagnet - Singlet Superconductor Junctions

Boris Kastening·Dirk K. Morr·Lambert Alff·Karl Bennemann
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Abstract

We study the Josephson current, I_J, in a junction consisting of two s-wave superconductors that are separated by a ferromagnetic barrier possessing a magnetic and non-magnetic scattering potential, g and Z, respectively. We discuss the general dependence of I_J on g, Z, and the phase difference ϕbetween the two superconductors. Moreover, we compute the critical current, I_c for given g and Z, and show that it possesses two lines of non-analyticity in the (g, Z)-plane. We identify those regions in the (g, Z)-plane where the Josephson current changes sign with increasing temperature without a change in the relative phase between the two superconductors, i.e., without a transition between a 0 and πstate of the junction. Finally, we show that by changing the relative phase ϕ, it is possible to tune the junction through a first-order quantum phase transition in which the spin polarization of the two superconductors' combined ground state changes from < S_z > =0 to < S_z > =1/2.

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Boris Kastening, Dirk K. Morr, Lambert Alff, Karl Bennemann. 2009-05-12. Charge Transport and Quantum Phase Transitions in Singlet Superconductor - Ferromagnet - Singlet Superconductor Junctions. https://arxiv.org/abs/cond-mat/0610283

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