Low thermal fluctuations in a system heated out of equilibrium

TL;DR

This study reveals that in a non-uniform heated system, mechanical fluctuations can remain at equilibrium levels despite high local temperatures, due to inhomogeneous dissipation mechanisms.

Contribution

It demonstrates that inhomogeneous dissipation can decouple fluctuation amplitude from average temperature in non-equilibrium systems.

Findings

Fluctuations are equivalent to equilibrium thermal noise despite high local temperatures.

Adding a coating restores expected fluctuation increase with temperature.

Inhomogeneous dissipation mechanisms can suppress fluctuation growth.

Abstract

We study the mechanical fluctuations of a micrometer sized silicon cantilever subjected to a strong heat flow, thus having a highly non-uniform local temperature. In this non-equilibrium steady state, we show that fluctuations are equivalent to the thermal noise of a cantilever at equilibrium around room temperature, while its mean local temperature is several hundred of degrees higher. Changing the mechanical dissipation by adding a coating to the cantilever, we recover the expected rise of fluctuations with the mean temperature. Our work demonstrates that inhomogeneous dissipation mechanisms can decouple the amplitude of thermal fluctuations from the average temperature. This property could be useful to understand out-of-equilibrium fluctuating systems, or to engineer low noise instruments.