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:

Twisted physics
A new study in the journal Nature shows that superconductivity in bilayer graphene can be turned on or off with a small voltage change, increasing its usefulness for electronic devices.
Physics vs. asthma
A research team from the MIPT Center for Molecular Mechanisms of Aging and Age-Related Diseases has collaborated with colleagues from the U.S., Canada, France, and Germany to determine the spatial structure of the CysLT1 receptor.
2D topological physics from shaking a 1D wire
Published in Physical Review X, this new study propose a realistic scheme to observe a 'cold-atomic quantum Hall effect.'
Helping physics teachers who don't know physics
A shortage of high school physics teachers has led to teachers with little-to-no training taking over physics classrooms, reports show.
Physics at the edge
In 2005, condensed matter physicists Charles Kane and Eugene Mele considered the fate of graphene at low temperatures.
Using physics to print living tissue
3D printers can be used to make a variety of useful objects by building up a shape, layer by layer.
When the physics say 'don't follow your nose'
Engineers at Duke University are developing a smart robotic system for sniffing out pollution hotspots and sources of toxic leaks.
The coming of age of plasma physics
The story of the generation of physicists involved in the development of a sustainable energy source, controlled fusion, using a method called magnetic confinement.
Physics: Not everything is where it seems to be
Scientists at TU Wien, the University of Innsbruck and the ÖAW have for the first time demonstrated a wave effect that can lead to measurement errors in the optical position estimation of objects.
'Fudge factors' in physics?
What if your theory to model and predict the electronic structure of atoms isn't accounting for dispersion energy?
More Physics News and Physics Current Events

Top Science Podcasts

We have hand picked the top science podcasts of 2019.
Now Playing: TED Radio Hour

Why do we revere risk-takers, even when their actions terrify us? Why are some better at taking risks than others? This hour, TED speakers explore the alluring, dangerous, and calculated sides of risk. Guests include professional rock climber Alex Honnold, economist Mariana Mazzucato, psychology researcher Kashfia Rahman, structural engineer and bridge designer Ian Firth, and risk intelligence expert Dylan Evans.
Now Playing: Science for the People

#541 Wayfinding
These days when we want to know where we are or how to get where we want to go, most of us will pull out a smart phone with a built-in GPS and map app. Some of us old timers might still use an old school paper map from time to time. But we didn't always used to lean so heavily on maps and technology, and in some remote places of the world some people still navigate and wayfind their way without the aid of these tools... and in some cases do better without them. This week, host Rachelle Saunders...
Now Playing: Radiolab

Dolly Parton's America: Neon Moss
Today on Radiolab, we're bringing you the fourth episode of Jad's special series, Dolly Parton's America. In this episode, Jad goes back up the mountain to visit Dolly's actual Tennessee mountain home, where she tells stories about her first trips out of the holler. Back on the mountaintop, standing under the rain by the Little Pigeon River, the trip triggers memories of Jad's first visit to his father's childhood home, and opens the gateway to dizzying stories of music and migration. Support Radiolab today at