University of Toronto Team Detects Hidden Octupolar Magnetism With Light

The focus is a phenomenon called octupolar order. Most magnets have two poles, north and south, or positive and negative. Recent advances in quantum mechanics have revealed an octupolar order in which a pattern of particles in a crystalline structure behaves as if it has eight magnetic poles rather than the familiar two.

The University of Toronto-led team said ordinary probes cannot detect this hidden magnetic state. By directing a special type of rotating light at magnetic materials, the researchers observed a clear optical fingerprint of the otherwise hidden magnetic order. The method uses light to probe the atomic vibrations produced as electrons spin, according to the report.

Arun Paramekanti, a professor in the Department of Physics and the Center for Quantum Information & Quantum Control in the Faculty of Arts & Science at the University of Toronto, is the senior author of the study. He said the team identified new signatures of a hidden type of magnetic state that cannot be detected using ordinary probes.

"We identified new signatures of a hidden type of magnetic state which cannot be detected using ordinary probes," Paramekanti said. "Our research opens up the possibility for using higher-order magnets in several applications including controllable read-write memory elements found in everyday computers."

According to the report, the findings offer a new tool for uncovering and manipulating previously inaccessible forms of magnetism. That capability could open new avenues for quantum technology development, the report said, and the researchers frame the work as an initial step toward using multipolar magnetism in practical devices.

The report describes octupolar order as a magnetic state beyond the two poles of ordinary magnets. The University of Toronto team's optical approach is intended to make such states observable without relying on ordinary magnetic probes.