For the first time, physicists have observed novel quantum effects in a topological insulator at room temperature. Researchers at Princeton University discovered that a material known as a topological insulator, made from the elements bismuth and bromine, exhibits specialized quantum behaviors no
Researchers at Princeton found that a material known as a topological insulator, made from the elements bismuth and bromine, exhibit specialized quantum behaviors normally seen only under extreme experimental conditions of high pressures and temperatures near absolute zero. Credit: Shafayat Hossain and M. Zahid Hasan of Princeton University
A topological insulator is the main device component used to investigate the mysteries of quantum topology. This is a unique device that acts as an insulator in its interior, which means that the electrons inside are not free to move around and therefore do not conduct electricity. However, the electrons on the device’s edgesfree to move around, meaning they are conductive.
However, Hasan and his team have developed an innovative way to bypass this problem. Building on their experience with topological materials and working with many collaborators, they fabricated a new kind of topological insulator made from bismuth bromide , which is an inorganic crystalline compound sometimes used for water treatment and chemical analyses.
“The kagome lattice topological insulators can be designed to possess relativistic band crossings and strong electron-electron interactions. Both are essential for novel magnetism,” said Hasan. “Therefore, we realized that kagome magnets are a promising system in which to search for topological magnet phases, as they are like the topological insulators that we discovered and studied more than ten years ago.
“In this case, in our experiments, we found a balance between spin-orbit coupling effects and large band gap width,” said Hasan. “We found there is a ‘sweet spot’ where you can have relatively large spin-orbit coupling to create a topological twist as well as raise the band gap without destroying it. It’s kind of like a balance point for the bismuth-based materials that we have been studying for a long time.
“We believe this finding may be the starting point of future development in nanotechnology,” said Shafayat Hossain, a postdoctoral research associate in Hasan’s lab and another co-first author of the study. “There have been so many proposed possibilities in topological technology that await, and finding appropriate materials coupled with novel instrumentation is one of the keys for this.”