Effect of spin-triplet correlations on Josephson transport in atomically thin Josephson structures containing half-metals

Spin polarized superconducting states are the subject of intense research since they are promising for application in the devices of superconducting spintronics. The basic system supporting such states consists of s-wave superconductor (S) and several ferromagnets (F). The noncollinear magnetization inside ferromagnets transforms spin-singlet Cooper pairs with spin projection sz=0 to the spin-triplet ones with sz=±1. In the recent experimental studies of spin-triplet S/FL/S'/FR/S device it was observed that the emergence of singlet superconductivity in the central S' layer leads to the decrease of the Josephson current. This situation is very different fr om one in spin-singlet S/S'/S structures, wh ere the emergence of superconductivity in the S' layer increases the spin-singlet Josephson current. To explain this puzzling experiment we have calculated the Josephson current in atomically thin S/HML/S'/HMR/S structure (HM is strong ferromagnet, “half-metal”) with spin-active S/HML,R interfaces in the framework of microscopic Gor'kov formalism and tight-binding model. We managed to show that the singlet superconducting gap in the S' layer indeed suppresses the triplet Josephson current. We also study the peculiarities of superconducting spin-triplet correlations in atomically thin S1/HM/S2 structures with spin-active S/HM interfaces. We use the combination of the microscopic Gor'kov formalism and tight-binding model allowing to obtain exact analytical results, which are valid beyond the quasiclassical approximation. In particular, we show that the spin-triplet Josephson critical current in S1/HM/S2 junction with two spin-active S/HM interfaces nonmonotonically depends on temperature. We also calculate the induced magnetic moment inside S2 layer in the S1/HM/S2 structure with spin-active S1/HM interface, which supports spin-triplet superconducting correlations. We show that the induced magnetic moment contain the components perpendicular to the spin-quantization axis (z axis) in HM. Moreover, the magnetic moment depends on the phase difference across the junction φ as Mx=m*cos φ, My=m*sin φ.
По статьям 1) S. Komori, J. M. Devine-Stoneman, K. Ohnishi, G. Yang, Z. Devizorova, S. Mironov, X. Montiel, L. A. O. Olthof, L. F. Cohen, H. Kurebayashi, et al., Science Advances 7, eabe0128 (2021).
2) Zh. Devizorova, S. Mironov, and A. I. Buzdin, Phys. Rev. B 103 (2021)