A new type of electricity-conducting effect has been found in room-temperature magnets, driven by a hidden quantum geometry that we are only just beginning to map.
April 24, 2026
Original Paper
Symplectic connection third-order Hall effect in a room-temperature ferromagnet
arXiv · 2604.20356
The Takeaway
Third-order nonlinear Hall effects in Fe3GaTe2 are driven by a geometric property called symplectic connection. This goes beyond the famous Berry curvature to reveal a more complex layer of how electrons move through a crystal lattice. The effect is particularly strong at room temperature, making it a viable candidate for actual electronic devices. It allows for the detection of magnetic states that are usually invisible to standard sensors. Mastering this hidden geometry could lead to the development of topological electronics that are faster and more energy-efficient than anything we have today.
From the abstract
Third-order nonlinear Hall effects (THE) have recently attracted considerable experimental interest as powerful probes for quantum geometric properties in emergent quantum materials, encompassing quadrupole moments of quantum metric and Berry curvature. Here, we report a fundamentally new THE in room-temperature van der Waals ferromagnet Fe3GaTe2 from second-order Berry connection polarizability, which manifests a higher-order characterization of band geometry called symplectic connection. Our o