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A European team led by UNIGE demonstrates the quantum metric in a topological insulator with unusual conductivity.
Ultra-fast data transfer and superconductivity: quantum materials offer significant technological prospects—if we can understand them at the atomic scale. A team from the University of Geneva (UNIGE), in collaboration with the University of Salerno, the Institute of Materials Science of Barcelona, and the National Research Council of Italy, has succeeded in observing the 'quantum metric' in a topological insulator — a unique geometric property of these materials, which conduct electricity only on the surface. Published in Nature Materials, this work represents a major step toward mastering the materials of the future.
Not all materials conduct electricity in the same way. These differences arise from the behavior of the electrons that make up the material. Among them, topological insulators—discovered in 2006—are of particular interest to scientists. Like conventional insulators, they block the flow of electric current inside them, yet, remarkably, allow it to flow freely across their surface.
This phenomenon is explained by the unique properties of electrons on the surface of the material. These properties could prove invaluable for the electronics of the future, particularly in the field of quantum computing. One such property is known as the 'quantum metric.' Measuring it allows scientists to describe the geometric structure of the space in which the electrons move.
The entire scientific community now has a new property to explore in the materials of the future.
New Observation of the 'Quantum Metric'
In 2025, a team led by Andrea Caviglia, full professor in the Department of Quantum Matter Physics (DQMP), Physics Section, UNIGE Faculty of Science, empirically measured this property for the first time—until then, it had existed only in theory. The experiment was conducted on a quantum material composed of strontium titanate and lanthanum aluminate. Now, in a new study carried out in collaboration with the University of Salerno, the Institute of Materials Science of Barcelona, and the Italian National Research Council, the team reports that it has succeeded in observing the same effect in a three-dimensional topological insulator. This breakthrough opens the way to better control of the electrical properties of next-generation materials.
"There are several families of topological insulators," explains Giacomo Sala, senior research associate in the Department of Quantum Matter Physics (DQMP), Physics Section, UNIGE Faculty of Science and lead author of the study. "The material we used in this work consists of antimony and tellurium, two metalloids with properties intermediate between those of metals and non-metals. It is one of the most extensively studied topological insulators to date, and its potential applications are highly promising."
Towards a Better Understanding of New Materials
"These new results extend and confirm our previous observations, which were obtained using a very different material. Moreover, they show that quantum metric effects can be controlled electrically," says Andrea Caviglia, who led the research. "The entire scientific community now has a new property to explore in the materials of the future, particularly to investigate how the geometric properties of electrons can reveal the fundamental nature of these materials." These materials could eventually replace the technologies currently used for data transfer, processing and storage.
