Figure 21.3 — Microscopic Stirling cycle

Fig. 21.3 — Microscopic Stirling cycle
Figure 21.3 — Microscopic Stirling cycle. (1) → (2), isothermal increase of the stiffness of the optical trapping potential (isothermal compression) at Tcold = 22C; (2) → (3), instantaneous temperature increase to Thot = 86C at fixed optical potential (isochoric process); (3) → (4), isothermal decrease of trap stiffness (isothermal expansion) at Thot ; (4) → (1), instantaneous temperature decrease to Tcold at fixed optical potential (isochoric process). The histograms show the measured particle probability distributions of the corresponding stationary states together with Gaussian fits as solid lines. The width of the distribution at Thot is 1.11 times greater than at Tcold for the same potential. This broadening is due to an increase of thermal energy. Inset: Stirling process in the pressure–volume diagram representation, where the enclosed area amounts to the work extracted by the machine.
Reprinted by permission from Macmillan Publishers Ltd: Blickle and Bechinger, Nature Phys. 8, 143–6, copyright 2012.