12/03/2018, 16:00 — 17:00 — Seminar room (2.8.3), Physics Building
Gershon Kurizki, Weizmann Institute of Science
Quantum and classical thermodynamic machines: work, power, cooling
Heat engine efficiency is limited by the Carnot bound. However, Scully et al. [Science 299, 862(2003)] bypassed this bound by allowing for extra heat input, and hence a higher hot-bath temperature, via coherence in the working fluid. In recent years, squeezed thermal baths have been claimed to yield extra heat input and hence surpass the Carnot bound [Rossnagel et al., PRL 112, 030602 (2014)]. However, the latter claim is unfounded, since squeezed baths transfer not just heat but also work to the working fluid, as shown by us [Gelbwaser-Klimovsky et al., NJP 18, 083012 (2016)]. Consequently, such engines are no longer heat engines but more like mechanical engines, and hence the Carnot bound is irrelevant to them. We have recently formulated a universal theory of any quantum or classical machines, fueled by arbitrary heat and work reservoirs [W. Niedenzu et al., Nature Commun. (2017)], which shows that what counts for maximal efficiency is the minimal loss of energy to the cold bath, which may be completely different from a Carnot bound if the baths are non-thermal. The crucial feature that allows for maximal work and power is maximized non-passivity (ergotropy) of the working fluid and/or the piston, as shown by us lately for a heat engine whose piston is squeezed by a pump [A. Ghosh et al., PNAS 2017]. Analogous considerations apply to cooling / refrigeration performance.