This illustration shows the novel topological insulator as a multiplexer. Image: Zhe Zhang/EPFL 2021.
This illustration shows the novel topological insulator as a multiplexer. Image: Zhe Zhang/EPFL 2021.

Topological insulators are materials with a molecular structure that forces photons and electrons to move only along the material’s boundary and only in one direction. These particles experience very little resistance and can travel freely past obstacles such as impurities, fabrication defects, a change in the trajectory of a signal within a circuit or objects placed intentionally in the particles’ paths.

This is because these particles, instead of being reflected by the obstacle, go around it “like river-water flowing past a rock”, says Romain Fleury, head of the Laboratory of Wave Engineering at the Ecole Polytechnique Fédérale de Lausanne (EPFL) in Switzerland.

Until now, these particles’ exceptional resilience to obstacles applied only to limited perturbations in the material, meaning this property couldn’t be exploited widely in photonics-based applications. That could soon change, however, thanks to research conducted by Fleury along with his PhD student Zhe Zhang and Pierre Delplace from the ENS Lyon Physics Laboratory in France.

This research involved designing a topological insulator in which the transmission of microwave photons can survive unprecedented levels of disorder. Fleury and his colleagues report their advance in a paper in Nature.

“We were able to create a rare topological phase that can be characterized as an anomalous topological insulator,” says Zhang. “This phase arises from the mathematical properties of unitary groups and gives the material unique – and unexpected – transmission properties.”

The discovery holds great promise for new advances in science and technology. “When engineers design hyperfrequency circuits, they have to be very careful to make sure that waves are not reflected but rather guided along a given path and through a series of components. That’s the first thing I teach my electrical engineering students,” says Fleury. “This intrinsic constraint, known as impedance matching, limits our ability to manipulate wave signals. However, with our discovery, we can take a completely different approach, by using topology to build circuits and devices without having to worry about impedance matching – a factor that currently restricts the scope of modern technology.”

Fleury’s lab is now working on concrete applications for their new topological insulator. “These types of topological circuits could be extremely useful for developing next-generation communication systems,” he says. “Such systems require circuits that are highly reliable and easily reconfigurable.” His research group is also looking at how this discovery could be used for developing new kinds of photonic processors and quantum computers.

This story is adapted from material from EPFL, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.