Nav: Home

NUS scientists discover how to 'lock' heat in place using quantum mechanics

July 09, 2019

A ground-breaking study conducted by researchers from the National University of Singapore (NUS) has revealed a method of using quantum mechanical wave theories to 'lock' heat into a fixed position.

Ordinarily, a source of heat diffuses through a conductive material until it dissipates, but Associate Professor Cheng-Wei Qiu from the Department of Electrical and Computer Engineering at the NUS Faculty of Engineering and his team used the principle of 'anti-parity-time (APT) symmetry' to show that it is possible to confine the heat to a small region of a metal ring without it spreading over time.

In the future, this newly demonstrated phenomenon could be used to control heat diffusion in sophisticated ways and optimise efficacy in systems that need cooling. The results of the study were published on 12 April 2019 in the prestigious scientific journal Science.

Freezing the spread of heat

"Imagine a droplet of ink in a flowing stream. After a short amount of time you would see the ink spread and flow in the direction of the current. Now imagine if that ink droplet stayed the same size and in the same position as the water flowed around it. Effectively that is what we have accomplished with the spread of heat in our experiment," explained Assoc Prof Qiu.

The experimental setup of this study is two oppositely rotating metal rings, sandwiched together with a thin layer of grease. The rotating motion of the rings act like the flow of the stream in the scenario. When heat is injected at a point in the system, the thermal energy is able to stay in position because one rotating ring is 'coupled' to the counter-rotating ring by the principles of APT symmetry.

The conditions of this experiment are quite precise in order for it to be successful. "From quantum mechanical theory, you can calculate the velocity needed for the rings. Too slow or too fast, and you will break the condition," said Assoc Prof Qiu. When the conditions are broken, the system acts conventionally, and the heat is carried forward as the ring rotates.

Bucking the trend

Applying the principles of APT symmetry to systems involving heat is a complete departure from the current school of thought in this area. "It's drastically different from the currently popular research topics. In this field, many groups are working on parity-time (PT) symmetry setups, and almost of them are looking at wave mechanics. This is the first time anyone has stepped out of the domain of waves, and shown that APT symmetry is applicable to diffusion-based systems such as heat," stated Assoc Prof Qiu.

This demonstration of a fixed area of heat within moving metal seems counterintuitive, as Assoc Prof Qiu admits, "Before this study, people actually thought this was a forbidden area, but we can explain all of it. It doesn't violate any laws of physics." In reality, the reason Assoc Prof Qiu and his team were able to control the heat was by introducing an extra degree of freedom into their ingenious experimental setup -- the rotation of the rings

"For APT symmetry to become significant in a system, there must be some element of loss and gain within the setup -- and they need to be balanced. In a traditional thermal diffusion system, APT symmetry is not consequential because there is no gain or loss degree of freedom. Hence, the mechanical rotation is the key player here," he explained.

Potential applications and next steps

Many modern technologies require the efficient removal of heat. Mechanical setups like engines, as well as computational and electrical components need to be effectively cooled. Currently, most technologies are cooled with a steady flow of liquid to take away the heat by convection.

"This experiment shows that we need to more careful when determining the flow rate and design of these systems," Assoc Prof Qiu stated. Whilst his experimental setup contained counter-rotating metal rings, the same principle could be applied to other setups in flux. "The perception is that the circulation will take away the heat simply, but it's not always necessarily so straightforward," he added.

Next, the team is looking to increase the size of their experiment. "At the moment our setup is in the range of centimetres, so we want to scale it up to the size of real motors or gearing systems. Gearing systems often have similar counter-rotating mechanisms which will generate heat, so we wish to apply theory to dissipate this heat more efficiently," Assoc Prof Qiu said.

National University of Singapore

Related Physics Articles:

Diamonds coupled using quantum physics
Researchers at TU Wien have succeeded in coupling the specific defects in two such diamonds with one another.
The physics of wealth inequality
A Duke engineering professor has proposed an explanation for why the income disparity in America between the rich and poor continues to grow.
Physics can predict wealth inequality
The 2016 election year highlighted the growing problem of wealth inequality and finding ways to help the people who are falling behind.
Physics: Toward a practical nuclear pendulum
Researchers from Ludwig-Maximilians-Universitaet (LMU) Munich have, for the first time, measured the lifetime of an excited state in the nucleus of an unstable element.
Flowers use physics to attract pollinators
A new review indicates that flowers may be able to manipulate the laws of physics, by playing with light, using mechanical tricks, and harnessing electrostatic forces to attract pollinators.
Physics, photosynthesis and solar cells
A University of California, Riverside assistant professor has combined photosynthesis and physics to make a key discovery that could help make solar cells more efficient.
2-D physics
Physicist Andrea Young receives a 2016 Packard Fellowship to pursue his studies of van der Waals heterostructures.
Cats seem to grasp the laws of physics
Cats understand the principle of cause and effect as well as some elements of physics.
Plasma physics' giant leap
For the first time, scientists are looking at real data -- not computer models, but direct observation -- about what is happening in the fascinating region where the Earth's magnetic field breaks and then joins with the interplanetary magnetic field.
Nuclear physics' interdisciplinary progress
The theoretical view of the structure of the atom nucleus is not carved in stone.

Related Physics Reading:

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Do animals grieve? Do they have language or consciousness? For a long time, scientists resisted the urge to look for human qualities in animals. This hour, TED speakers explore how that is changing. Guests include biological anthropologist Barbara King, dolphin researcher Denise Herzing, primatologist Frans de Waal, and ecologist Carl Safina.
Now Playing: Science for the People

#SB2 2019 Science Birthday Minisode: Mary Golda Ross
Our second annual Science Birthday is here, and this year we celebrate the wonderful Mary Golda Ross, born 9 August 1908. She died in 2008 at age 99, but left a lasting mark on the science of rocketry and space exploration as an early woman in engineering, and one of the first Native Americans in engineering. Join Rachelle and Bethany for this very special birthday minisode celebrating Mary and her achievements. Thanks to our Patreons who make this show possible! Read more about Mary G. Ross: Interview with Mary Ross on Lash Publications International, by Laurel Sheppard Meet Mary Golda...