Pair Tunneling as a Probe of Fluctuations in Superconductors

We suggest a method of using the average pair field of one superconductor to probe the fluctuation pair field of a second metal at temperature above the latter's superconducting transition point. The two metals should be fabricated as a strongly coupled tunnel junction and the dc I-V characteristic measured as a function of both the bias voltage V and the amplitude of a magnetic field H parallel to the junction interface. The resultant I-V characteristic is predicted to give a direct measurement of the frequency and wave-vector dependence of the Δ susceptibility characteristic of the superconducting transition.