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Charge-spin coupling in room-temperature 2D ferromagnetic material

What if electricity and magnetism, usually considered as separate or even competing forces in materials, could actually work together in harmony?

Researchers at National Taiwan University have demonstrated that electric and magnetic quantum states can synchronize at the atomic scale in a room-temperature two-dimensional (2D) ferromagnet. Their study, recently in Nature Communications, offers new insight into how different quantum behaviors can interact coherently.

The team focused on Fe₅GeTe₂, a novel 2D ferromagnetic material that retains its magnetic properties even at room temperature. Unlike typical materials where magnetism and electrical conduction occur independently, Fe₅GeTe₂ is unique. Its iron atoms contain electrons that play dual roles—contributing both to magnetic order and electrical conduction. This dual nature sets the stage for an unusual level of interaction between quantum states.

Using high-resolution scanning tunneling microscopy (STM), the researchers observed three quantum phenomena occurring simultaneously: charge density waves (CDWs), the Kondo effect, and ferromagnetism. Even more strikingly, these states were not acting independently. Instead, they showed a synchronized spatial pattern—a kind of quantum "coherence" that had been theorized but never directly seen.

The key lies in a special type of iron atom that helps organize these effects into a √3 × √3 superlattice pattern. This discovery challenges conventional thinking in quantum materials research and could serve as a foundation for the development of multifunctional quantum devices.

"This is the first direct experimental evidence of atomic-scale coupling between charge, spin, and many-body effects in a room-temperature 2D ferromagnet," said Prof. Ya-Ping Chiu.