Quantum Materials Link Light and Magnetism

Scientists are exploring atomically thin quantum materials where light and magnetism interact directly. Researchers at the City College of New York are reviewing progress in this field. These materials are only a few atoms thick. They exhibit unusual interactions between light, electric charge, and magnetism.

This research could lead to advanced optoelectronic devices and quantum technologies. These technologies would manipulate light, charge, and electron spin together. The review, published in *Nature Materials*, focuses on layered magnetic semiconductors. In these materials, light-generated excitations called excitons interact with magnetic order and magnetic waves called magnons.

An exciton forms when light energizes an electron, creating a linked electron-hole pair. Magnons are collective waves that travel through a material's magnetic structure. Unlike previous methods, van der Waals magnetic semiconductors allow excitons and magnetic moments to arise from the same electronic orbitals. This shared origin enables direct interaction between light and magnetism within the material.

Excitons can enhance magneto-optical effects, allowing scientists to identify magnetic states by observing changes in light polarization. Magnetic order can also change exciton energy and confinement. Interactions between excitons and magnons can link optical signals with gigahertz-frequency magnetic activity. Hybrid particles called exciton polaritons, which combine properties of light and matter, can transport optical information.

Potential applications include magneto-photonic memory, all-optical logic, and adjustable light-emitting devices. Quantum transducers, which convert signals between microwave and optical frequencies, are another promising application. These could connect components in future quantum networks.

Despite rapid progress, the field has many unexplored areas. Many materials need further study. Scientists also need better theoretical models to predict complex interactions between excitons, electron spins, lattice vibrations, and photons.