Fig. 4: Physical mechanism with calculated conductance and shot noise.
a Proximity-induced superconducting spin-triplet gap in Fe layer (blue), ΔF, and the interfacial spin-orbit coupling (SOC) support multiple spin-flip Andreev reflections in the V/MgO/Fe junction, which give rise to the excess charge transport (5e in the sketch) and the resulting low-bias excess Fano factor, h denotes holes. b Bias-dependent conductance without (black) and with SOC (colored lines) for different relative magnitudes of the induced spin-triplet gap, ΔF, and the spin-singlet gap, ΔS, in vanadium. Without SOC, there is a reduced junction transparency and conductance for all V. For comparison with experimental measurements, each curve with SOC is normalized by its conductance value well above the superconducting gap. The barrier and SOC strengths are parameterized by Z = 1 and λ= 1.2 (see Methods). c Calculated Fano factor or, equivalently, the effective charge ratio |q | /e, as a function of applied bias for the same parameters and a color code as given in (b). Inset: The corresponding evolution of the effective charge ratio (at eV/Δs = 0.1) and the conductance peak position with relative increase in ΔF. The gray area denotes the commonly expected Fano factor limited by 2.
