A subtle geometric quality of electrons has been directly observed, according to physicists who have uncovered a potentially promising new avenue for future electronics and quantum technologies.
Based on new findings by an international collaboration led by University of Geneva (UNIGE) researchers, a property physicists call the quantum metric has been measured within a three-dimensional topological insulator, revealing that it can be controlled using electricity.
The discovery, reported in a new paper appearing in Nature Materials, extends our known capabilities in terms of experimental investigation of the unusual geometries of quantum materials.
A Tale of Quantum Topology
With interiors that resist the flow of electrical current similar to conventional insulators, topological insulators differ by offering an unusual combination of physical properties that includes the ability for electrons to still move along their surfaces.
These exterior electrons aren’t just transporters of electrical charge, though. Their quantum states possess geometric qualities that also govern the behavior of the materials themselves. One component of this is the quantum metric, a property that essentially describes the rate at which an electron’s quantum state can change in proportion to changes in its momentum.
Directly observing this property in lab experiments had remained a stubborn problem in the past. That changed last year, however, as a result of work by a UNIGE team led by physicist Andrea Caviglia, during which the first known empirical measurement of the quantum metric within a different quantum material was successfully recorded.
“There are several families of topological insulators,” said Giacomo Sala, a senior research associate in the UNIGE DQMP and the new study’s primary author.
For their research, the team turned to a well-studied topological insulator composed of antimony and tellurium.
“The material we used in this work consists of antimony and tellurium, two metalloids with properties intermediate between those of metals and non-metals,” Sala said, noting that “It is one of the most extensively studied topological insulators to date, and its potential applications are highly promising.”
Exploring the Quantum Metric
The researchers were also successful in demonstrating that effects associated with the quantum metric can be adjusted electrically. This is significant, since it potentially offers a pathway through which scientists can manipulate the geometric qualities of electronic quantum states, and do so in practical ways.
Caviglia said the team’s results “extend and confirm our previous observations, which were obtained using a very different material,” adding that they “show that quantum metric effects can be controlled electrically.”
The team’s findings also provide researchers with a new experimental basis for exploring the fundamental behavior of quantum materials, while opening new paths to the investigation of materials that may eventually play roles in advanced electronics and quantum technologies.
“The entire scientific community now has a new property to explore in the materials of the future,” Cavigila said in a statement, “particularly to investigate how the geometric properties of electrons can reveal the fundamental nature of these materials.”
The team’s research was detailed in the study, “Probing the quantum metric of 3D topological insulators,” which was published in Nature Materials.
Micah Hanks is the Editor-in-Chief and Co-Founder of The Debrief. A longtime reporter on science, defense, and technology with a focus on space and astronomy, he can be reached at micah@thedebrief.org. Follow him on X @MicahHanks, and at micahhanks.com.