Stationary and transient Fluctuation Theorems for effective heat flux between hydrodynamically coupled particles in optical traps

TL;DR

This study experimentally investigates the statistical properties of heat fluxes between hydrodynamically coupled particles in optical traps, confirming fluctuation theorems in both stationary and transient states under effective temperature differences.

Contribution

It demonstrates the validity of exchange fluctuation theorems for heat fluxes in a coupled Brownian particle system with an imposed temperature gradient, including transient and stationary regimes.

Findings

Heat fluxes satisfy exchange fluctuation theorem in stationary state.

Transient xFT holds immediately after applying temperature gradient.

Total heat flux satisfies asymptotic xFT over long times.

Abstract

We experimentally study the statistical properties of the energy fluxes between two trapped Brownian particles, interacting through dissipative hydrodynamic coupling, submitted to an effective temperature difference $\Delta T$, obtained by random forcing the position of one trap. We identify effective heat fluxes between the two particles and show that they satisfy an exchange fluctuation theorem (xFT) in the stationary state. We also show that after the sudden application of a temperature gradient $\Delta T$, \resub{the total} hot-cold flux satisfies \resub{a} transient xFT for any integration time whereas \resub{the total} cold-hot flux only does it asymptotically for long times.