NEST, Scuola Normale Superiore &Istituto Nanoscienze-CNR, Pisa I-56126, Italy.
ICTP, Strada Costiera 11, Trieste 34151, Italy.
Nat Commun. 2016 Jun 20;7:11895. doi: 10.1038/ncomms11895.
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.
自大约两个世纪前诞生以来，热力学一直激发着人们持续的兴趣和提出基本问题。根据第二定律，没有热机的效率可以大于卡诺效率。后者可以由卡诺热机实现，然而卡诺热机理想地在无限长的时间内运行，因此输出为零功率。一个当前开放的问题是，卡诺效率是否可以在有限的功率下实现。以前的大多数工作都是在线性响应理论的昂萨格矩阵形式框架内解决这个问题的。在这里，我们基于有限尺寸标度理论采用了不同的方法。我们专注于量子奥托热机，并表明当工作物质处于二级相变的边缘时，发散的能量涨落可以使热机在不牺牲功率的情况下接近卡诺点。这种接近的速度由临界指数决定，因此展示了我们分析的普遍性。
