Controlling thermal radiation, once considered a random phenomenon, is opening up new perspectives thanks to the work of researchers at the University of Vienna and the University of Manchester. These discoveries promise to revolutionize our understanding and control of heat emitted by materials.
Thermal radiation, generally governed by the laws of statistical physics, can now be controlled. A team of researchers, led by Prof. Stefan Rotter from the Institute of Theoretical Physics at TU Wien, in collaboration with Coskun Kocabas from the University of Manchester, has demonstrated that thermal radiation can be precisely manipulated. This discovery was published in the journal Science.
When a piece of metal is heated, its color depends solely on its temperature. Neither the material, nor the geometry, nor the structure of its surface influence this color. However, researchers have shown that, thanks to innovative methods linked to mathematical topology, thermal radiation can be emitted only at specific points.
Material properties and topology
A material’s properties, such as its ability to absorb light or conduct electricity, depend on subtle details like the presence of specific atoms. Even small disturbances can change the behavior of a material sample.
According to Stefan Rotter, “in practice, it is desirable to have material properties that are as stable as possible, which are not immediately destroyed by small changes“. This is why particular attention is paid to the topological properties of materials.
Topology, a branch of mathematics, deals with the fundamental properties of geometric objects. For example, a donut is topologically different from a bun because it has a hole in the center. This topological stability is also found in materials research, where certain properties can remain stable despite disturbances.
The coast of the British Isles as a model of thermal radiation
The joint project showed that the radiation behavior of objects can be described topologically. This makes it possible to develop special coatings to control thermal radiation in new ways.
A combination of specific metal layers creates topological effects, allowing thermal radiation to escape only at specific points. “It is possible to restrict thermal radiation to completely arbitrary shapes», explains Stefan Rotter. The Manchester researchers chose a map of the British Isles to illustrate this concept.
By creating a special multi-layer coating, thermal radiation is emitted only along the coast, where the thickness of the top layer differs between land and sea. This phenomenon allows thermal radiation to be generated only at points defined by the coast of the British Isles.
Implications and openings
Topological effects have already been recognized in other contexts, as evidenced by the 2016 Nobel Prize in Physics. The application of these concepts to thermal radiation represents a significant advance. The presented experiment constitutes a proof of concept of these techniques, paving the way for a multitude of other technically interesting effects.
The researchers are confident that this discovery could lead to innovative applications in various fields, ranging from thermal management of materials to the design of advanced optical devices.
Illustration legend: Thermal radiation; But thanks to topological tricks, it is possible to make a surface emit thermal radiation only at certain points, which makes it possible to create an image, for example a map of the British Isles.
Article: “MS Ergoktas et al, Localized thermal emission from topological interfaces”, Science 384, 6700. https://arxiv.org/abs/2401.08316
