Current Rectification in Junctions with Spin-Split Superconductors

Spin-split superconductors exhibit an electron-hole asymmetric spin-resolved\ndensity of states, but the symmetry is restored upon averaging over spin. On\nthe other hand, asymmetry appears again in tunneling junctions of spin-split\nsuperconductors with a spin-polarized barrier. As demonstrated recently in both\ntheory and experiment, this fact leads to a particularly strong thermoelectric\neffect in superconductor-ferromagnet structures. In this work we show another\nimportant effect stemming from the electron-hole asymmetry - current\nrectification. We calculate the charge current in spin-polarized tunnel\njunctions of normal metal and a spin-split superconductor with AC and DC\nvoltage bias. In the DC case, the I-V curve is not fully antisymmetric and has\na voltage-symmetric component due to spin polarization. This translates to the\nexistence of a rectified current in the AC case, which is proportional to the\nspin polarization of the junction and strongly depends on the frequency of the\napplied bias. We discuss possible applications of the rectification effect,\nincluding a diode for superconducting electronics and radiation detectors. The\nanalysis of the rectified charge current is supplemented by the discussion of\nheat current and relevant noise correlators, where electron-hole asymmetry also\nplays an important role, and which are useful for applications in detectors.\n