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, ∇T. The voltage is proportional to I∇T at a given temperature, in agreement with the prediction of Pethick and Smith, and diverges as (1-TTc)^-1 for given values of I and ∇T.