Controlling thermodynamics of a quantum heat engine with modulated amplitude drivings

TL;DR

This paper investigates how amplitude modulation of external drives influences the thermodynamics of a quantum heat engine, revealing new control mechanisms and deviations in efficiency bounds due to geometric effects.

Contribution

It introduces envelope functions in amplitude modulation to control geometric effects, enabling optimization of flux and noise, and challenges existing efficiency bounds in quantum heat engines.

Findings

Envelope modulation provides additional thermodynamic control.

Geometric effects alter efficiency at maximum power.

Universal efficiency bounds may not hold under certain modulation conditions.

Abstract

External driving of bath temperatures with a phase difference of a nonequilibrium quantum engine leads to the emergence of geometric effects on the thermodynamics. In this work, we modulate the amplitude of the external driving protocols by introducing envelope functions and study the role of geometric effects on the flux, noise and efficiency of a four-level driven quantum heat engine coupled with two thermal baths and a unimodal cavity. We observe that having a finite width of the modulation envelope introduces an additional control knob for studying the thermodynamics in the adiabatic limit. The optimization of the flux as well as the noise with respect to thermally induced quantum coherences becomes possible in presence of geometric effects, which is hitherto not possible with sinusoidal driving without an envelope. We also report the deviation of the slope and generation of an intercept in the standard expression for efficiency at maximum power as a function of Carnot efficiency in presence of geometric effects under the amplitude modulation. Further, a recently developed universal bound on the efficiency obtained from thermodynamic uncertainty relation is shown not to hold when a small width of the modulation envelope along with a large value of cavity temperature is maintained.