Thermal noise of a cryo-cooled silicon cantilever locally heated up to its melting point

Alex Fontana (1) , Richard Pedurand (1, 2, 3) , Vincent Dolique (1) , Ghaouti Hansali (4, 2, 3) , Ludovic Bellon (1)

1 Phys-ENS - Laboratoire de Physique de l'ENS Lyon
2 LMA - Laboratoire des matériaux avancés
3 IP2I Lyon - Institut de Physique des 2 Infinis de Lyon
4 ENISE - Ecole Nationale d'Ingénieurs de Saint Etienne

The Fluctuation-Dissipation Theorem (FDT) is a powerful tool to estimate the thermal noise of physical systems in equilibrium. In general however, thermal equilibrium is an approximation, or cannot be assumed at all. A more general formulation of the FDT is then needed to describe the behavior of the fluctuations. In our experiment we study a micro-cantilever brought out-ofequilibrium by a strong heat flux generated by the absorption of the light of a laser. While the base is kept at cryogenic temperatures, the tip is heated up to the melting point, thus creating the highest temperature difference the system can sustain. We independently estimate the temperature profile of the cantilever and its mechanical fluctuations, as well as its dissipation. We then demonstrate how the thermal fluctuations of all the observed degrees of freedom, though increasing with the heat flux, are much lower than what is expected from the average temperature of the system. We interpret these results thanks to a minimal extension of the FDT: this dearth of thermal noise arises from a dissipation shared between clamping losses and distributed damping.

Keywords: Thermal noise; Non-equilibrium steady state; Equipartition; Out-of-equilibrium statistical physics

Domains: Statistical Mechanics [cond-mat.stat-mech]

Alex Fontana, Richard Pedurand, Vincent Dolique, Ghaouti Hansali, Ludovic Bellon. Thermal noise of a cryo-cooled silicon cantilever locally heated up to its melting point. Physical Review E : Statistical, Nonlinear, and Soft Matter Physics, 2021, 103, pp.062125. ⟨10.1103/PhysRevE.103.062125⟩. ⟨ensl-03117929v2⟩