The power of a critical heat engine

TL;DR

This paper explores how quantum Otto engines operating near second order phase transitions can approach Carnot efficiency at finite power, leveraging diverging energy fluctuations and critical phenomena.

Contribution

It introduces a finite-size-scaling approach to quantum heat engines, revealing universal conditions under which Carnot efficiency can be approached at finite power.

Findings

Diverging energy fluctuations enable near-Carnot efficiency at finite power.

Critical indices determine the rate of approach to Carnot efficiency.

Universal behavior across different systems near phase transitions.

Abstract

Since its inception about two centuries ago thermodynamics has sparkled continuous interest and fundamental questions. According to the second law no heat engine can have an efficiency larger than Carnot's efficiency. The latter can be achieved by the Carnot engine, which however ideally operates in infinite time, hence delivers null power. A currently open question is whether the Carnot efficiency can be achieved at finite power. Most of the previous works addressed this question within the Onsager matrix formalism of linear response theory. Here we pursue a different route based on finite-size-scaling theory. We focus on quantum Otto engines and show that when the working substance is at the verge of a second order phase transition diverging energy fluctuations can enable approaching the Carnot point without sacrificing power. The rate of such approach is dictated by the critical indices, thus showing the universal character of our analysis.