of Rochester, NY (United States) Sponsoring Org.: USDOE Office of Science (SC), Basic Energy Sciences (BES) National Science Foundation (NSF) OSTI Identifier: 1852438 Grant/Contract Number: SC0017890 PHY-1748958 Resource Type: Accepted Manuscript Journal Name: Physical Review. of Rochester, NY (United States) Chapman Univ., Orange, CA (United States) Chalmers University of Technology, Gothenburg (Sweden).Our investigation brings new perspectives about the connection between cyclic and steady-state engines. We show that such stochastic cycles are made possible because the work extraction mechanism is itself stochastic instead of the periodic time dependence in the working-substance Hamiltonian which can be found in conventional mechanical engines. We identify the cycle mainly responsible for the engine performance and quantify its statistics with tools from graph theory.

Using a stochastic thermodynamic approach, we quantify the cycle fluctuations and relate them to the entropy produced during individual cycles.

In particular, these cycles fluctuate in direction and duration and occur in competition with other spurious cycles. The cycles are purely stochastic, in contrast to mechanical autonomous engines which exhibit self-oscillations. In single realizations of the dynamics of this steady-state engine autonomous, four-stroke cycles can be identified. One dot is tunnel-coupled to a hot reservoir serving as a heat source, the other one to two electrically biased reservoirs at a colder temperature, such that work is extracted under the form of a steady-state current against the bias. Here, we analyze a steady-state thermoelectric engine, whose working substance consists of two capacitively coupled quantum dots.

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