A team led by physicist Vinod M. Menon at the City College of New York has published a sweeping review in Nature Materials that charts one of the fastest-growing frontiers in modern physics: materials just a few atoms thick in which light, electric charge, and magnetism are no longer separate phenomena but deeply entwined.
The review, titled "Excitons in van der Waals magnetic materials," focuses on a class of layered crystals known as van der Waals magnetic semiconductors. In conventional materials, optical and magnetic properties tend to operate independently. In these ultrathin systems, that separation breaks down entirely.
What excitons and magnons actually do
The review centres on two types of quasiparticles. Excitons form when incoming light excites an electron inside a material, causing it to leave behind a positively charged vacancy called a hole. The electron and hole remain bound together as a neutral particle that still interacts strongly with light. Magnons, by contrast, are collective waves that ripple through a material's organised magnetic structure, carrying information about the spin of millions of atoms at once.
In van der Waals magnetic semiconductors, these two quasiparticles arise from the same electronic orbitals inside the crystal, giving them an unusually direct route to interact. According to Phys.org, this allows light and magnetism to couple intrinsically rather than through the indirect, engineered routes researchers had previously relied on, such as layering a semiconductor on top of a separate magnetic material.
“"In these materials, light and magnetism no longer operate as separate channels. An exciton is not just a passive light-driven excitation sitting on top of the magnetism. It can sense the spin order and magnons, and under the right conditions, even help control the magnetic state itself." — Pratap Chandra Adak, postdoctoral researcher and lead author, City College of New York”
From lab curiosity to practical technology
The review maps several phenomena that have now been observed across two-dimensional magnets. Excitons can sharply amplify magneto-optical effects, making it possible to read out a material's magnetic state simply by observing how it changes the polarisation of light passing through it. Magnetic order, in turn, can tune exciton energies and spatial confinement, while exciton-magnon coupling can link optical signals to gigahertz-frequency magnetic dynamics.
The potential applications catalogued by the team are wide-ranging. They include magneto-photonic memory and data readout, all-optical logic circuits, adjustable light-emitting devices, and polaritonic technologies, in which hybrid light-matter particles carry optical information through a material. The review also highlights quantum transducers: devices that convert signals between microwave and optical frequencies, a capability that could become important for connecting components in future quantum networks.
“"Over the past few years, this field has moved from detecting magnetism in atomically thin crystals to actively exploring how magnetic order can control light-matter interactions. The goal of this article is to bring those developments into a coherent framework and identify where the field can go next." — Vinod M. Menon, professor of physics and senior author”
A field with significant gaps still to fill
The review is candid about the obstacles ahead. Many candidate materials remain only partially explored, and researchers currently lack the predictive theoretical tools needed to describe how excitons, spins, lattice vibrations, and photons interact simultaneously within the same system. The authors highlight moiré magnetic excitons, where two slightly misaligned crystal layers create interference patterns that trap excitons, as one of the most promising unexplored directions.
The paper is an international collaboration. Co-authors include Florian Dirnberger of the Technical University of Munich, Akashdeep Kamra of Rheinland-Pfälzische Technische Universität Kaiserslautern-Landau in Germany, and Xiaodong Xu of the University of Washington, reflecting the broad global investment in this emerging field. The review was published in Nature Materials with the DOI 10.1038/s41563-026-02636-0.
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