All materials do not conduct electricity in the same way. This difference depends on the behavior of the electrons that compose them. Among them, topological insulators, discovered in 2006, particularly intrigue scientists. These materials block the passage of electric current inside, like conventional insulators, while allowing it to flow on their surface.
This phenomenon is explained by the particular properties of the electrons present on their surface. These could prove useful for future electronics, particularly in the field of quantum computing. One of these properties, called the "quantum metric," describes the geometric properties of the space in which electrons move.
Similar to an emergent curvature of space embedded in quantum materials, the quantum metric distorts electronic trajectories on the surface of topological insulators.
© Xavier Ravinet - UNIGE
The entire scientific community now has a new property to explore future materials.
New observation of the "quantum metric"
In
2025, the team of Andrea Caviglia, full professor at the Department of Quantum Matter Physics (DQMP) of the Section of Physics at the Faculty of Science, had empirically measured this property, previously only theoretical. The experiment was conducted on a quantum material composed of strontium titanate and lanthanum aluminate.
Today, in a new study conducted with the University of Salerno, the Institute of Materials Science of Barcelona, and the Italian National Research Council, Andrea Caviglia's team announces that they have observed the same effect in a three-dimensional topological insulator. This first observation paves the way for better control of the electrical properties of next-generation materials.
"There are several families of topological insulators," explains Giacomo Sala, scientific collaborator at the DQMP of UNIGE and first author of the study. "The one we used here is composed of antimony and tellurium, two metalloids with properties intermediate between metals and non-metals. It is one of the most studied topological insulators to date, and its applications look promising."
Towards better mastery of new materials
"These new results extend and confirm our previous observations, obtained on a very different material. Furthermore, they demonstrate that effects related to the quantum metric can be controlled electrically," rejoices Andrea Caviglia, who led this work.
"The entire scientific community now has a new property to explore future materials, particularly to examine how the geometric properties of electrons can reveal the deep nature of these materials." In the long term, they could supplant current technologies used for data transfer, processing, and storage.