Chromium, nickel compounds offer quantum material path

Researchers at the City College of New York have detailed a new path for quantum materials, focusing on atomically thin systems where light, magnetism, and electric charge strongly interact. A review article in Nature Materials titled “Excitons in van der Waals magnetic materials” surveys recent advances by the team in layered magnetic semiconductors, where light-generated excitons interact with magnetic ripples called magnons.

“In these materials, light and magnetism no longer operate as separate channels,” said Pratap Chandra Adak, a postdoctoral researcher in Vinod M. Menon’s Laboratory for Nano and Micro Photonics and lead author of the Review. This work could enable optoelectronic and quantum technologies by directly linking optical signals to magnetic dynamics.

Van der Waals Materials Couple Excitons, Magnons, and Light

Van der Waals magnetic semiconductors present a new approach to coupling light and magnetism, differing from previous methods that relied on adding magnetic elements to existing semiconductors. Researchers can now observe direct interactions between light and magnetic properties because both excitons and magnetic moments originate from the same electronic orbitals within the crystal structure.

This intrinsic connection, detailed in a Nature Materials review led by the City College of New York, bypasses the limitations of extrinsic methods and opens pathways for novel optoelectronic devices. The review article surveys advances in materials like chromium triiodide, nickel phosphorus trisulfide, and chromium sulfur bromide, demonstrating how excitons, light-generated electronic excitations, can significantly enhance magneto-optical effects.

These enhanced effects allow for the reading of magnetic states through changes in light polarization, a capability crucial for developing new data storage and processing technologies. Magnetic order itself can be used to fine-tune the energies and spatial confinement of excitons, offering a degree of control previously unattainable. This precise manipulation of exciton behavior is essential for creating efficient and tailored light-emitting devices. Researchers have also observed that coupling between excitons and magnons, collective ripples in a material’s magnetic order, can link optical signals to magnetic dynamics occurring at gigahertz frequencies. Vinod M.

Menon, professor of physics and senior author of the review, notes a shift in the field over the past few years. “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,” he said, emphasizing the progression from observation to active manipulation. The team’s work focuses on understanding and harnessing these interactions to create exciton-polaritons, hybrid light-matter particles capable of carrying optical information through a material.

This capability is particularly relevant for developing magneto-photonic memory and readout systems, all-optical logic gates, and tunable light-emitting devices. The potential applications extend beyond conventional optoelectronics, reaching into quantum technologies; researchers envision these materials serving as quantum transducers, devices that convert signals between microwave and optical frequencies, a critical component for building future quantum networks.

Several challenges remain, including the need for more comprehensive material exploration and improved theoretical models to accurately describe the simultaneous interactions between excitons, spins, lattice vibrations, and photons. Promising areas for future research include the investigation of moiré magnetic excitons, optical control of spin textures, and the pursuit of magnetic exciton-polariton condensation, all of which could unlock further advancements in this rapidly evolving field.

According to Menon, the goal of the review is “to bring those developments into a coherent framework and identify where the field can go next,” potentially leading to a new generation of quantum materials and devices.