Long-range superharmonic Josephson current and spin-triplet pairing correlations in a junction with ferromagnetic bilayers

AbstractThe long-range spin-triplet supercurrent transport is an interesting phenomenon in the superconductor/ferromagnet ("Equation missing") heterostructure containing noncollinear magnetic domains. Here we study the long-range superharmonic Josephson current in asymmetric "Equation missing" junctions. It is demonstrated that this current is induced by spin-triplet pairs "Equation missing" − "Equation missing" or "Equation missing" + "Equation missing" in the thick "Equation missing" layer. The magnetic rotation of the particularly thin "Equation missing" layer will not only modulate the amplitude of the superharmonic current but also realise the conversion between "Equation missing" − "Equation missing" and "Equation missing" + "Equation missing". Moreover, the critical current shows an oscillatory dependence on thickness and exchange field in the "Equation missing" layer. These effect can be used for engineering cryoelectronic devices manipulating the superharmonic current. In contrast, the critical current declines monotonically with increasing exchange field of the "Equation missing" layer and if the "Equation missing" layer is converted into half-metal, the long-range supercurrent is prohibited but "Equation missing" still exists within the entire "Equation missing" region. This phenomenon contradicts the conventional wisdom and indicates the occurrence of spin and charge separation in present junction, which could lead to useful spintronics devices.