The approach could lead to a new solid state cooling technology for future microprocessors that will have so many transistors packed in a little space that current methods can not remove heat quickly enough.
for using photon cooling devices, says Pramod Reddy, who manages the work with Edgar Meyhofer, the two professors in mechanical engineering.
The first, known in the field as laser cooling, is based on the founding work of Arthur Ashkin, who shares the Nobel Prize in Physics in 2018.
Instead, the researchers used the chemical potential of heat radiation – a concept that is used more often to explain, for example, how a battery works. Suppose the chemical potential of the radiation is zero, Meihofer says. "But the theoretical work dating back to the 1980s suggests that under certain conditions this is not the case."
The chemical potential of the battery, for example, drives electrical current when placed in a device. Inside the battery, metal ions want to flow to the other side because they can get rid of some energy – chemical potential energy – and we use this energy as electricity. Electromagnetic radiation, including visible light and infrared heat radiation, usually has no such potential.
"Usually for heat radiation, the intensity depends only on temperature, but we actually have an extra button to control that radiation, which makes the cooling we are exploring possible," says Linsiao Zhou, a research associate in engineering and lead author of this In theory, turning the positive and negative electrical connections of the infrared LED will not just stop it from the emission of light but will actually suppress the heat radiation it has to produce yes, just because it is at room temperature, with this inversion of bias, behaves as if it is at a lower temperature, says Reddy. "However, measuring this cooling – – It's terribly complicated
To get enough infrared light from an object in the LED, the two would have to be extremely close together – less than one wavelength of infrared light. This is necessary to take advantage of "close-range" or "short-range" effects that allow more infrared photons or light particles to pass from the object to be cooled in the LED.
The Reddy and Mehofer team had a foot up because they had already heated and cooled nano-sized devices, arranging them to be only a few dozen nanometers apart – or less than a thousandth of a hair. In this immediate vicinity, the photon that would not escape the object to be cooled may switch to the LED, almost as if the distance between them does not exist. And the team had access to an ultra-low vibration lab, where measurements of nanodimetric objects were made possible because the vibrations, like those from others in the building, were dramatically reduced.
The group proved the principle by building a miniature calorimeter, which is a device that measures energy changes and places it on a miniature LED with a size of rice grain. These two are constantly emitting and receiving thermal photons from one another and everywhere in their environment.
"Every object that is at room temperature emit light, and a night vision camera actually captures the infrared light coming from a warm body."
But once the LED is inverse, it starts to act as a very low- , absorbing the photons from the calorimeter, at the same time, the gauge prevents heat from flowing back into the calorimetry by conduction, resulting in a cooling effect
The team showed a cooling of 6 watts per square meter, theoretically this effect could lead to a quench equivalent to 1000 watts per square meter, or the power of sunlight on the Earth's surface
This may be important for future smartphones and other computers, with more computing power in smaller and smaller devices , removing heat from the microprocessor begins to limit how much energy can be pressed in a space
With the improvements in efficiency and cooling rate of this new approach, the team predicts this phenomenon as a way to quickly separate heat from a microprocessor in the devices. He may even oppose the abuses suffered by smartphones as nano-sized dividers could provide a separation between the microprocessor and the LED. entitled "Photon cooling in the near field by controlling the chemical potential of photons."
Interference as a new method for cooling quantum devices
Near-Photon Cooling by Controlling the Chemical Potential of Photons, Nature (2019). DOI: 10.1038 / s41586-019-0918-8, https://www.nature.com/articles/s41586-019-0918-8