Catenaa, Saturday, February 07, 2026-Scientists in Switzerland have demonstrated that a laser pulse can reversibly control the magnetic polarity of a topological ferromagnet, opening possibilities for light-reconfigurable electronic devices.
Researchers at the University of Basel and ETH Zurich used a twisted bilayer of the organic semiconductor molybdenum ditelluride to achieve the effect. In the material, electrons act as tiny bar magnets, aligning their spins to produce ferromagnetism. Traditionally, reversing polarity requires heating above a critical temperature, allowing spins to rearrange. In this experiment, a laser pulse alone triggered a flip without heating.
The process leverages topological states, which are robust electronic configurations that cannot be smoothly transformed into one another. By tuning the electrons between topological insulating and metallic conducting states, the team could manipulate collective spin alignment, making the entire ferromagnet switch polarity. The dynamics of the flip were influenced by the material’s topological state, linking magnetism and topology in a controllable platform.
The researchers also demonstrated that the laser could define boundaries of topological ferromagnetic regions repeatedly, enabling dynamical control at micrometer scales. The orientation of electron spins was verified using a second, weaker laser to measure reflected light, confirming the polarity switch.
Future applications include optically writing adaptable topological circuits on chips, creating tiny interferometers capable of detecting minute electromagnetic fields, and developing light-controlled electronic components. This work integrates electron interactions, topology, and dynamic optical control in a single experiment, marking a significant advance in condensed matter physics.
