Supercurrent-Induced Charge Imbalance Measured in a Superconductor in the Presence of a Thermal Gradient

A pair-quasiparticle potential difference arising from a quasiparticle charge imbalance has been observed in superconducting tin films along which there exist both a supercurrent, $I$, and a temperature gradient, $\ensuremath{\nabla}T$. The voltage is proportional to $I\ensuremath{\nabla}T$ at a given temperature, in agreement with the prediction of Pethick and Smith, and diverges as ${(1\ensuremath{-}\frac{T}{{T}_{c}})}^{\ensuremath{-}1}$ for given values of $I$ and $\ensuremath{\nabla}T$.