Fig. 2: Rectification of the superconducting tunnel diode.
a Schematic of the N/FI/S tunnel junction. The path of the tunneling current is indicated by the black line and its arrows. In terms of electronic circuit elements this junction behaves like the indicated diode: the current flows preferentially from the Al layer to the Cu layer while the reverse flow is inhibited. b Current-to-Voltage (I(V)) characteristics of the junction measured at T ≃ 50 mK, B = 0.1 T in the four-wire configuration (i). c Symmetric and antisymmetric parts of the I(V) characteristic of panel c showing a sizable symmetric component of the current. d Rectification coefficient R(V) = ISym(V)/IAntisym(V) evaluated from e (black line) along with the comparison with the rectification extracted from the approximated analytical model \(R=P\tanh [eV/(2{K}_{B}T)]\) (blue line) and the full numerical ones (red line). Details of the numerical model can be found in the Methods section, specifically in Eqs. (3) and (14). Notice the good qualitative agreement with the simplified model predicting the saturation at R ≃ P ∼ 40% at 225–280 μV. The model ceases to work when eV ≳ Δ − h ∼ 250 μeV. The discrepancy between the analytical model and the experiment mostly comes from weak inelastic scattering, and to a lesser extent from spin relaxation and orbital depairing.
