Thermoelectric voltage at metallic point contacts from nonequilibrium effects

This paper presents results for thermoelectric voltage experiments carried out with metallic point contacts. The motivation for this work is the fundamental understanding of the nonequilibrium state between electrons and phonons, and for applying this phenomenon to a point temperature measurement of small heating elements like an LSI (Large-Scale Integration) electronic chip. The experiments were carried out by using gold, silver, copper, and tungsten point contacts under cryogenic conditions, and a heat flux through the point contact was applied via a temperature difference across the contact. In this condition, thermoelectric voltages appeared even when the entire open circuit consisted of only one material. This phenomenon was explained theoretically by considering the nonequilibrium effect between the phonon and electron temperatures, and the geometric effect at the point contact. Good agreement was found between the theory and the experiment.