2014/03/28 by Meng, Hao, Wu, Jiansheng, Wu, Xiuqiang +2
#FOS: Physical sciences #Superconductivity (cond-mat.supr-con)
paper · doi:10.48550/arxiv.1403.7337
The long-range spin-triplet supercurrent transport is an interesting phenomenon in the superconductor/ferromagnet (S/F) heterostructure containing noncollinear magnetic domains. Here we study the long-range superharmonic Josephson current in asymmetric S/F1/F2/S junctions. It is demonstrated that this current is induced by spin-triplet pairs |\uparrow\uparrow⟩-|\downarrow\downarrow⟩ or |\uparrow\uparrow⟩+|\downarrow\downarrow⟩ in the thick F1 layer. The magnetic rotation of the particularly thin F2 layer will not only modulate the amplitude of the superharmonic current but also realise the conversion between |\uparrow\uparrow⟩-|\downarrow\downarrow⟩ and |\uparrow\uparrow⟩+|\downarrow\downarrow⟩. Moreover, the critical current shows an oscillatory dependence on thickness and exchange field in the F2 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 F1 layer, and if the F1 layer is converted into half-metal, the long-range supercurrent is prohibited but |\uparrow\uparrow⟩ still exists within the entire F1 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.