Extended Nyquist formula for a resistance subject to a heat flow

Benjamin Monnet (1) , Sergio Ciliberto (1) , Ludovic Bellon (1)

1 Phys-ENS - Laboratoire de Physique de l'ENS Lyon

The Nyquist formula quantifies the thermal noise driven fluctuations of voltage across a resistance in equilibrium. We deal here with the case of a resistance driven out of equilibrium by putting it in contact with two thermostats at different temperatures. We reach a non-equilibrium steady state where a heat flux is flowing through the resistance. Our measurements demonstrate anyway that a simple extension of the Nyquist formula to the non uniform temperature field describes with an excellent precision the thermal noise. For a metallic ohmic material, the fluctuations are actually equivalent to those of a resistance in equilibrium with a single thermostat at the mean temperature between the hot and cold sources.

Mots clés: Johnson noise; Nysquit formula; Thermal noise; NESS; non-equilibrium; heat conduction

Domaines: Mécanique statistique [cond-mat.stat-mech]

Benjamin Monnet, Sergio Ciliberto, Ludovic Bellon. Extended Nyquist formula for a resistance subject to a heat flow. 2019. ⟨ensl-02148352v1⟩