Study highlights noise-power tradeoff in nanoscale heat engines

Using nanoscale devices as small as human cells, researchers can create materials with revolutionary properties that enable smaller, faster, and more energy-efficient electronic devices. However, to fully exploit the potential of nanotechnology, it is essential to address the problem of noise.

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

Nanotechnology is advancing rapidly and is attracting widespread interest in sectors such as communications and energy production. At the nanoscale, equivalent to one millionth of a millimeter, particles adhere to the laws of quantum mechanics. By exploiting these properties, materials can be designed to exhibit improved conductivity, magnetism, and energy efficiency.

“Today we are witnessing the tangible impact of nanotechnology: nanoscale devices are the ingredients for faster technologies and nanostructures make materials for energy production more efficient,” says Janine Splettstösser, Professor of Applied Quantum Physics at Chalmers.

Devices smaller than a human cell unlock new electronic and thermoelectric properties

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

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

Navigating nanoscale noise: a crucial challenge

Noise, however, is a major obstacle to the advancement of nanotechnology research. This disruptive noise is created by electrical charge fluctuations and thermal effects inside devices, which impairs the precision and reliability of performance. Despite considerable efforts, researchers have not yet determined to what extent this noise can be eliminated without impeding energy conversion, and our understanding of its mechanisms remains limited. But a research team at Chalmers has managed to take an important step in the right direction.

In their study, “Out-of-Equilibrium Fluctuation-Dissipation Bounds” published as an editor’s suggestion in Physical Exam LettersThey studied nanoscale thermoelectric heat engines. These specialized devices are designed to control and convert waste heat into electrical energy.

“All electronic devices emit heat, and much effort has recently been made to understand how, at the nanoscale, this heat can be converted into useful energy. Tiny thermoelectric heat engines take advantage of quantum mechanical properties and non-thermal effects and, like tiny power plants, can convert heat into electrical energy rather than wasting it,” says Professor Splettstösser.

Balancing noise and power in nanoscale heat engines

However, nanoscale thermoelectric heat engines work best when subjected to large temperature differences. These temperature variations make noise already difficult for researchers to study and understand. But Chalmers researchers have now managed to shed light on a critical trade-off between noise and power in thermoelectric heat engines.

“We can prove that there is a fundamental constraint regarding noise that directly affects the performance of the ‘engine’. For example, we can not only see that if we want the device to produce a lot of power, we have to tolerate higher noise levels, but also the exact amount of noise,” explains Ludovico Tesser.

“This clarifies a trade-off relationship, namely the amount of noise one must endure to extract a specific amount of energy from these nanoscale engines. We hope that these results can serve as a guideline in the field of designing high-precision nanoscale thermoelectric devices.”