Brownian heat engine with active reservoirs.

Area of Science:

• Physics
• Biophysics
• Statistical Mechanics

Background:

• Microorganisms like bacteria function as active matter, consuming energy and exhibiting run-and-tumble motion.
• Active environments created by microbial swarms are nonequilibrium systems with distinct noise characteristics compared to thermal equilibrium.
• A key difference is the colored noise in active environments, featuring a finite and significant persistence time.

Purpose of the Study:

• To investigate a mesoscopic energy-harvesting device (engine) utilizing active reservoirs.
• To analyze the performance of such a device by harnessing the colored noise properties of active environments.
• To explore the potential for exceeding conventional thermodynamic limits in energy harvesting.

Main Methods:

• An exactly solvable linear model was employed to study the energy-harvesting engine.
• The model incorporated active reservoirs with colored noise characteristics.
• A novel definition for active-reservoir temperature was proposed and utilized.

Main Results:

• The active engine's performance was shown to surpass that of an equilibrium environment.
• The engine efficiency was demonstrated to exceed the conventional Carnot bound, releasing the power-efficiency trade-off constraint.
• Efficiency at maximum power was found to exceed the Curzon-Ahlborn efficiency.
• This enhancement stems from unconventional entropy production due to the non-Markovian nature of active reservoirs.

Conclusions:

• Active reservoirs offer superior performance for energy-harvesting devices compared to equilibrium ones.
• The proposed active engine design can overcome traditional thermodynamic limitations like the Carnot bound.
• The efficiency enhancement is linked to non-Markovian effects and unconventional entropy production.
• The study highlights the critical role of timescale symmetry between active reservoirs for optimal engine performance.