Squeezed thermal reservoirs as a resource for a nano-mechanical engine beyond the Carnot limit

Jan Klaers, Stefan Faelt, Atac Imamoglu, Emre Togan

Published 2017-03-29Version 1

The efficient conversion of thermal energy to mechanical work by a heat engine is an ongoing technological challenge. Since the pioneering work of Carnot [1], it is known that the efficiency of heat engines is bounded by a fundamental upper limit - the Carnot limit. Advances in micro- and nano-technology however, allow for testing concepts derived from thermodynamics in limits where the underlying assumptions no longer hold [2, 3, 4, 5, 6, 7]. Extremely miniaturized forms of heat engines have been experimentally realized, where the working medium is represented by a single particle instead of 10^23 particles as in the macroscopic world [8, 9, 10, 11, 12]. Theoretical studies suggest that the efficiency of heat engines may overcome the Carnot limit by employing stationary, non-equilibrium reservoirs that are characterized by a temperature as well as further parameters, for example quantum coherent [13], quantum correlated [14, 15] and squeezed thermal reservoirs [16, 17, 18]. In a proof-of-principle experiment, we demonstrate that the efficiency of a nano-beam heat engine coupled to squeezed thermal noise is not bounded by the standard Carnot limit. Remarkably, we also show that it is possible to design a cyclic process that allows for extraction of mechanical work from a single squeezed thermal reservoir. Our results demonstrate a qualitatively new regime of non-equilibrium thermodynamics at small scales and provide a new perspective on the design of efficient, highly miniaturized engines [19].