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

Abstract

Abstract The long-range spin-triplet supercurrent transport is an interesting phenomenon in the superconductor/ferromagnet ("Equation missing"<!-- image only, no MathML or LaTex -->) heterostructure containing noncollinear magnetic domains. Here we study the long-range superharmonic Josephson current in asymmetric "Equation missing"<!-- image only, no MathML or LaTex --> junctions. It is demonstrated that this current is induced by spin-triplet pairs "Equation missing"<!-- image only, no MathML or LaTex --> − "Equation missing"<!-- image only, no MathML or LaTex --> or "Equation missing"<!-- image only, no MathML or LaTex --> + "Equation missing"<!-- image only, no MathML or LaTex --> in the thick "Equation missing"<!-- image only, no MathML or LaTex --> layer. The magnetic rotation of the particularly thin "Equation missing"<!-- image only, no MathML or LaTex --> layer will not only modulate the amplitude of the superharmonic current but also realise the conversion between "Equation missing"<!-- image only, no MathML or LaTex --> − "Equation missing"<!-- image only, no MathML or LaTex --> and "Equation missing"<!-- image only, no MathML or LaTex --> + "Equation missing"<!-- image only, no MathML or LaTex -->. Moreover, the critical current shows an oscillatory dependence on thickness and exchange field in the "Equation missing"<!-- image only, no MathML or LaTex --> 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"<!-- image only, no MathML or LaTex --> layer and if the "Equation missing"<!-- image only, no MathML or LaTex --> layer is converted into half-metal, the long-range supercurrent is prohibited but "Equation missing"<!-- image only, no MathML or LaTex --> still exists within the entire "Equation missing"<!-- image only, no MathML or LaTex --> 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.