The RIKEN Institute, a national research institute in Japan, has built a microscopic engine that both generates heat and cools at the same time. This is the first device that embodies quantum effects and can be used to improve nanotechnology.
Conventional heat and cooling engines achieve different effects by cycling two cylinders of liquid. Compressing one cylinder of liquid causes the liquid to heat up; rapidly expanding the other cylinder causes it to cool down. By cycling the two cylinders of liquid, energy is exchanged to achieve the effect of a heat engine or a refrigerator.
Keiji Ono of the Advanced Equipment Laboratory at the RIKEN Institute, who led the study, says that building a machine that can achieve both cycles at the macroscopic level is an impossible task, and certainly useless.
But in the microscopic world, the laws of physics are different. The microscopic world is the world controlled by quantum science, which has many differences from the macroscopic world. For example, an electron can appear in two positions at the same time, or have two energy states at the same time. Physicists are constructing new theoretical frameworks and conducting corresponding experiments to understand the operation of microscopic systems. In recent years, scientists have built a number of microscopic devices, such as those based on individual atoms.
This new study uses an electron inside a transistor to create a quantum version of a heat engine. The electron has two energy states. The team increases or decreases the energy difference between the two by applying an electric field or microwaves.
Says Keiji Ono, “It’s like the periodic cycles of expansion and compression of a liquid inside a confinement.” Microwaves are also released when an electron transitions from a high-energy state to a low-energy state.
By monitoring which energy state the electrons are in, the team first demonstrated the effect of the nanodevice as a heat engine and a cooling machine, respectively.
Then, the team demonstrated something even more peculiar: the nanodevice could simultaneously heat and cool – a manifestation of the quantum effect. The researchers confirmed the existence of this phenomenon by probing the characteristic effect map of electrons in different energy states.
The experimental demonstration of the characteristic effect map is almost identical to that predicted by theory,” said Keiji Ono. This means that the two modes of operation can be switched quickly between, which will have innovative applications in the future.”
This study was recently published in Physical Review Letters.
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