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

Abstract

The long-range spin-triplet supercurrent transport is an interesting phenomenon in the superconductor/ferromagnet () heterostructure containing noncollinear magnetic domains. Here we study the long-range superharmonic Josephson current in asymmetric junctions. It is demonstrated that this current is induced by spin-triplet pairs − or + in the thick layer. The magnetic rotation of the particularly thin layer will not only modulate the amplitude of the superharmonic current but also realise the conversion between − and + . Moreover, the critical current shows an oscillatory dependence on thickness and exchange field in the 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 layer, and if the layer is converted into half-metal, the long-range supercurrent is prohibited but still exists within the entire 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.

Observation of the dominant spin-triplet supercurrent in Josephson spin valves with strong Ni ferromagnets

“…To conclude, both singlet and triplet supercurrents can flow through S/F heterostructures [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. The unique feature of our work that adds to further understanding of the triplet state, along with earlier experimental works [17][18][19][20][21][22][23][24][25][26][27][28], was development of in-situ characterization techniques for an accurate assessment of micromagnetic states in actual nano-devices.…”

“…Pairing correlations survive over a certain time/distance, during which precession of spins in exchange field may create a correlated triplet pair. The corresponding odd-frequency spin-triplet order parameter has been predicted theoretically using various approaches [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. This inspired intense experimental search for this exotic state in Superconductor/Ferromagnet (S/F) heterostructures [17][18][19][20][21][22][23][24][25][26][27][28][29].…”

In situ transport characterization of magnetic states in Nb/Co superconductor/ferromagnet heterostructures

“…Competition between spin-polarized ferromagnetism and spinsinglet superconductivity leads to a variety of interesting phenomena including the possible generation of the odd-frequency spin-triplet order parameter [1][2][3]. In recent years, this exotic state has been extensively studied both theoretically [4][5][6][7][8][9][10][11][12][13][14][15][16][17] and experimentally [18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35] in various superconductor/ferromagnet (S/F) heterostructures. It is anticipated, that this phenomenon can be employed for the creation of novel superconducting devices, in which the supercurrent is determined and controlled by the magnetic state of the heterostructure, that is, by the relative orientation of magnetizations in several F-layers [18,19,22,23,[25][26][27][28][29][30]…”

Transport characterization of magnetic states in Superconductor/Ferromagnet Nb/Co multilayers

“…Competition between spin-polarized ferromagnetism and spin-singlet superconductivity leads to a variety of interesting phenomena including possibile generation of the odd-frequency spin-triplet order parameter [1][2][3]. In recent years this exotic state has been extensively studied both theoretically [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] and experimentally [19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34] in various Superconductor/Ferromagnet (S/F) heterostructures. It is anticipated, that this phenomenon can be employed for creation of novel superconducting devices, in which supercurrent is determined and controlled by the magnetic state of the heterostructure, i.e., by the relative orientation of magnetizations in several F-layers [19,20,23,24,[26][27][28][29][30][31][32]…”