Study sheds light on noise-power trade-off in nano-scale heat engines

With nanoscale devices as small as human cells, scientists can create breakthrough material properties that lead to smaller, faster, more energy-efficient electronics. But to fully realize nanotechnology’s potential, addressing the noise is key.

A research team from Chalmers University of Technology in Sweden has taken a significant step towards unraveling fundamental constraints on noise, paving the way for future nanoelectronics.

Nanotechnology is advancing rapidly, gaining widespread interest in industries such as communications and energy production. At the nanoscale—a millionth of a millimeter—molecules obey the laws of quantum mechanics. By exploiting these properties, materials can be designed to exhibit increased conductivity, magnetism, and energy efficiency.

“Today we are witnessing the tangible impact of nanotechnology – nano-scale devices are the building blocks of faster technologies and nanostructures are increasing the efficiency of materials used to produce energy,” says Janine Splettstösser, professor of applied quantum physics at Chalmers University.

Devices Smaller Than a Human Cell Unlock New Electronic and Thermoelectric Properties

To manipulate charge and energy currents down to the level of a single electron, scientists use so-called nanoscale devices, systems smaller than human cells. These nanoelectronic systems can act as “tiny engines” that perform specific tasks by exploiting the properties of quantum mechanics.

“At the nanoscale, devices can have completely new and desirable properties. These devices, which are a hundred to ten thousand times smaller than a human cell, allow the design of highly efficient energy conversion processes,” says Ludovico Tesser, a PhD student in applied quantum physics at Chalmers University of Technology.

Navigating Nano-Noise: A Critical Challenge

However, noise is a significant obstacle to the development of nanotechnology research. This disturbing noise is caused by fluctuations in electrical charge and thermal effects inside the devices, which makes precise and reliable operation difficult. Despite extensive efforts, scientists have not yet discovered to what extent this noise can be eliminated without hindering energy conversion, and our knowledge of its mechanisms remains limited. However, a research team at Chalmers has now managed to take an important step in the right direction.

In his study “Out-of-Equilibrium Fluctuation-Dissipation Bounds” published at the suggestion of the editor in Physical inspection lettersinvestigated nano-scale thermoelectric heat engines. These specialized devices are designed to control and convert waste heat into electrical energy.

“All electronic devices emit heat, and much recent effort has been devoted to understanding how this heat can be converted into usable energy at the nano level. Tiny thermoelectric heat engines use quantum mechanical properties and non-thermal effects and, like tiny power plants, can convert heat into electrical energy instead of letting it go to waste,” says Professor Splettstösser.

Balancing Noise and Power in Nano-Scale Heat Engines

However, nanoscale thermoelectric heat engines perform better when exposed to significant temperature differences. These temperature fluctuations make the already difficult noise that scientists grapple with even more difficult to study and understand. But now, researchers at Chalmers have managed to shed light on the critical trade-off between noise and power in thermoelectric heat engines.

“We can prove that there is a fundamental noise limit that has a direct impact on the performance of the ‘engine’. For example, we can see not only that if you want a device to produce a lot of power, you have to tolerate a higher noise level, but also a precise amount of noise,” says Ludovico Tesser.

“It explains the trade-off relationship—how ​​much noise you have to put up with to get a given amount of power out of these nanoscale engines. We hope these findings can serve as guidelines for the design of high-precision nanoscale thermoelectric devices.”