Researchers implement single-atom heat engine
Since the inception of the Industrial Revolution, thermal engines, or heat engines, play a pivotal technology in technology and economy. They convert thermal energy (heat) into mechanical work – for instance in the engines that drive our cars. At the same time, the trend towards miniaturisation yields ever-smaller devices. The scientists gathered in the Quantum working group of the Johannes Gutenberg University of Mainz utilised a quadrupole ion trap (aka Paul trap) to store a single electrically charged calcium atom. The atom can be heated up through electrical noise and cooled by means of laser rays. Thus, it passes through a thermodynamic cycle comparable to the cycles in a classical thermal engine such as a steam engine or an internal combustion engine. The power generated is converted into atomic vibrations. Hence, the atom in this experiment functions as engine and at the same time as energy storage.
The physicists were able to characterize the thermodynamic behaviour of the motor through extended series of measurements. In an article published recently in the magazine “Science”, they explain that the motor has a remarkable power of 10 to 22 watts, albeit at a very low efficiency of just 0.3 percent. The scientists however utilise something like a “thermodynamic reverse mode”, explained Johannes Rossnagel, author of the Science article. “By reversing the thermodynamic cycle, we turn the motor into a single-atom refrigerator”, the scientist said.
Beyond any application consideration, the significance of the research lies in the fact that it provides insights into the thermodynamics of single particles. As a next step the scientist group plans to further reduce the operating temperature of the “machine” and explore thermodynamic quantum effects. In other theoretical works it has been suggested to increase the efficiency of thermal engines through what the scientist call a quantum bath. This offers multiple options to go beyond the paradigms of classical thermodynamics and design innovative motors.
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