Heat Engines play a prominent role in our modern civilization since the industrial revolution. In general, heat engines convert thermal energy into mechanical motion and form the basis for all motorized vehicles, from cars to airplanes. At the same time miniaturization led to the development of increasingly smaller devices in the past decades. The thermodynamics team in Mainz deals with the question whether those machines can be scaled down to the ultimate single particle level, while retaining the same working principles as, for instance, those of a car engine.
In recent experiments, in collaboration with University of Kassel and University of Erlangen-Nuremberg, we have demonstrated that it is possible to convert thermal energy from different heat sources into useful mechanical motion, using a single Calcium-ion as working fluid . Therefore we confine the single ion in a special designed linear Paul trap with tapered geometry. We engineer a coupling to thermal reservoirs using detuned laser radiation or tailored electronic noise on the trap electrodes. By coupling the ion to these reservoirs the radial thermal state of the ion is heated and cooled alternately. Thus the ion performs a thermodynamic cycle similar to a Stirling cycle. During each cycle the heating and cooling processes lead to the production of a finite amount of work. Due to the mode-coupling, which results from the funnel potential of the trap, the work of the cycle leads to a force along the trap axis. If the cycle is repeated resonantly with the eigenfrequency of the ion in axial direction, the change in temperature in the radial state is transduced into a coherent oscillation along the trap axis. This oscillation can in principle be used to drive any other oscillatory system.
In extensive measurements we have characterized the performance the single atom heat engine. We have measured output powers of up to 10^-22 Watts and efficiencies up to 0.3%. Due to the light weight of the single atom engine, the power to mass ratio is comparable to those of macroscopic car engines.
For further details, theoretical analysis and scientific results we refer to our relevant publications:
Johannes Rossnagel, Samuel Thomas Dawkins, Karl Nicolas Tolazzi, Obinna Abah, Eric Lutz, Ferdinand Schmidt-Kaler, Kilian Singer,
"A single-atom heat engine",
arXiv:1510.03681 , (2015)
Roßnagel, K. N. Tolazzi, F. Schmidt-Kaler, K. Singer,
"Fast thermometry for trapped ions using dark resonances",
New Journal of Physics 17, 045004 (2015)