Making more magnetism possible with topology

MIT researchers show how topology can help create magnetism at higher temperatures. Researchers who have been working for years to understand electron arrangement, or topology, and magnetism in certain semimetals have been frustrated by the fact that the materials only display magnetic properties if they are cooled to just a few degrees above absolute zero. A new MIT study led by Mingda Li, associate professor of nuclear science and engineering, and co-authored by Nathan Drucker, a graduate research assistant in MIT's Quantum Measurement Group and PhD candidate in applied physics at Harvard University, along with Thanh Nguyen and Phum Siriviboon, MIT graduate students working in the Quantum Measurement Group, is challenging that conventional wisdom. The open-access research,  published in  Nature Communications , for the first time shows evidence that topology can stabilize magnetic ordering, even well above the magnetic transition temperature - the point at which magnetism normally breaks down. "The analogy I like to use to describe why this works is to imagine a river filled with logs, which represent the magnetic moments in the material," says Drucker, who served as the first author of the paper. "For magnetism to work, you need all those logs pointing in the same direction, or to have a certain pattern to them. But at high temperatures, the magnetic moments are all oriented in different directions, like the logs would be in a river, and magnetism breaks down. "But what's important in this study is that it's actually the water that's changing," he continues. "What we showed is that, if you change the properties of the water itself, rather than the logs, you can change how the logs interact with each other, which results in magnetism." A surprising connection between topology and magnetism