by Ellen Neff, Columbia University Quantum Initiative
edited by Gaby Clark, reviewed by Robert Egan

Upon ultrafast laser pulse excitation, coherent ferrons, also called polarization waves, emit THz outward and propagate inside the material. Credit: Zhu Lab, Columbia University

In new research published in Nature Materials, a team of researchers led by Columbia University chemist Xiaoyang Zhu, in collaboration with fellow Columbians Xavier Roy, Milan Delor, Dmitri Basov, and James McIver, has observed coherent ferrons for the first time.

Ferrons are electronic quasiparticles, predicted since the 1960s, that carry polarization. The oscillating polarization wave that the team, led by Columbia postdocs Jeongheon Choe and Taketo Handa, observed represents a new type of information carrier that could prove much faster than conventional electronics.

In ferroelectric materials, the dipole moments of unit cells line up, becoming polarized. Collective excitation of these dipoles creates the ferron quasiparticle, which has an inherent dipole moment. This means one side of each tiny particle is slightly more negatively charged than the other. Ferrons are similar to another quasiparticle that's been of interest to Zhu and colleagues in recent years: magnons.

Magnons are quasiparticles that carry spin (the property that makes magnets magnetic). In 2022, Zhu's former postdoc, Eunice Bae, now an assistant professor at Cornell University, observed coherent magnon waves rippling through a 2D magnet and coupled to much higher-energy quasiparticles called excitons. Not long after Bae's discovery, Handa observed puzzling but strong oscillations in the terahertz (THz) emission signal from a ferroelectric material called NbOI₂, synthesized by members of Roy's group.

At the time, Handa was studying the material's unique optical properties¡ªit can very efficiently convert near-infrared light to broadband terahertz radiation¡ªbut he and Choe were inspired to take a closer look at these oscillations. "Ferrons, conceptually, are the electric analogs of magnons," said Choe. "If magnons can propagate through a material, why not ferrons?"

And indeed, they can. Using spectroscopic techniques, Choe observed that the ferrons can collectively move as a coherent wave at hypersonic speeds across the material, while also emitting THz radiation. In collaborator Milan Delor's lab, graduate student Andre Liston directly imaged the fast propagation of the coherent ferrons using stroboSCAT microscopy. "This is a very comprehensive demonstration of how coherent ferrons behave in 2D ferroelectric materials," Choe said.

Similar to how magnons have growing implications for both classical and quantum forms of memory, coherent ferrons are promising information carriers. In the study, for example, the team generated THz-frequency ferrons, the frequency expected for next-generation high-speed telecommunications. The extreme confinement of THz waves in these materials may find a broad range of applications, particularly in 6G communications technologies. And with its small footprint, it should also be straightforward to integrate NbOI₂ into on-chip technologies.

"This is the exciting beginning of ferronics," said Handa. "We are excited to now deepen our understanding of ferrons and their fundamental properties, and to build foundations for future technologies."

Publication details

Jeongheon Choe et al, Observation of coherent ferron emission and propagation, Nature Materials (2026). DOI: 10.1038/s41563-026-02597-4

Journal information: Nature Materials