Length scale for the superconducting Nernst signal above Tc in Nb0.15 Si0.85

We present a study of the Nernst effect in amorphous superconducting thin films of Nb0.15 Si0.85. The field dependence of the Nernst coefficient above Tc displays two distinct regimes separated by a field scale set by the Ginzburg-Landau correlation length (CL). A single function F(ξ), with the CL as its unique argument set either by the zero-field CL (in the low magnetic field limit) or by the magnetic length (in the opposite limit), describes the Nernst coefficient. We conclude that the Nernst signal observed on a wide temperature (30× Tc) and field (4× Bc2) range is exclusively generated by short-lived Cooper pairs.