Importantly, when \(V_{S1}\) is reversed in sign a similar drag current pattern is achieved, and more important, the sign of the drag current \(I_2\) is kept the same for the two \(V_{S1}\) bias directions.

Considering now \(I_2\) versus \(-\epsilon_1\) and taking compared with \(G_1\) (drive current) we observe certain correlation between both curves, sometimes they are correlated \(-\epsilon_1\approx 0.1 meV\approx E_C\) or anti-correlated \(-\epsilon_1\approx E_C+|e|V_{S1}\approx 0.6 meV\).