Researchers on the City College of Recent York are charting a fast-growing area of quantum science centered on materials only just a few atoms thick. In these systems, light, electric charge, and magnetism are closely connected moderately than behaving independently.
The work comes from physicist Vinod M. Menon’s Laboratory for Nano and Micro Photonics (LaNMP). Researchers imagine these unusual interactions could eventually support advanced optoelectronic devices and quantum technologies that manipulate light, charge, and electron spin together.
When Light and Magnetism Interact
In a review published in Nature Materials, titled “Excitons in van der Waals magnetic materials,” the researchers examine recent progress involving layered magnetic semiconductors. These materials allow light-generated excitations called excitons to interact with magnetic order and with magnetic waves often known as magnons.
An exciton forms when incoming light energizes an electron and causes it to maneuver, abandoning a positively charged “hole.” The electron and hole remain linked, forming an electrically neutral particle that may still interact strongly with light. Magnons are different. They’re collective waves that travel through the organized magnetic structure of a cloth.
Scientists have spent years attempting to unite the optical properties of exciton-rich semiconductors with magnetism. Earlier strategies included adding magnetic atoms to semiconductors or stacking atomically thin semiconductors on top of magnetic materials.
Van der Waals magnetic semiconductors provide a more direct approach. Inside these crystals, excitons and magnetic moments can emerge from the identical electronic orbitals. This shared origin allows light and magnetism to influence each other contained in the material itself.
“In these materials, light and magnetism now not operate as separate channels,” said Pratap Chandra Adak, a postdoctoral researcher in Menon’s group and lead creator of the Review. “An exciton isn’t only a passive light-driven excitation sitting on top of the magnetism. It could possibly sense the spin order and magnons, and under the precise conditions, even help control the magnetic state itself.”
Reading Magnetic States With Light
The Review examines several essential material platforms, including chromium triiodide, nickel phosphorus trisulfide, and chromium sulfur bromide. Research on these two-dimensional magnets has revealed several ways in which excitons and magnetic behavior can affect one another.
Excitons can significantly strengthen magneto-optical effects, allowing scientists to discover magnetic states by observing changes within the polarization of sunshine. Magnetic order may also alter the energy of excitons and influence where they’re confined inside a cloth.
Interactions between excitons and magnons can connect optical signals with magnetic activity occurring at gigahertz frequencies. The researchers also discuss exciton polaritons, hybrid particles that mix properties of sunshine and matter and might transport optical information through a cloth.
“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,” said Menon, professor of physics and senior creator of the Review. “The goal of this text is to bring those developments right into a coherent framework and discover where the sphere can go next.”
Recent Possibilities for Quantum Technology
The researchers discover several potential applications that will rely upon precise control of sunshine and magnetism at extremely small scales. These include magneto-photonic memory and data readout, all-optical logic, adjustable light-emitting devices, magneto-optic lasers, and polaritonic technologies.
One other promising application involves quantum transducers. These devices convert signals between microwave and optical frequencies, a capability that might grow to be essential for connecting components in future quantum networks.
Major Scientific Challenges Remain
Despite the rapid progress, much of this field stays unexplored. Many possible materials haven’t yet been studied intimately, and scientists still need higher theoretical models that may predict how excitons, electron spins, lattice vibrations, and photons behave after they interact at the identical time.
Future research could investigate moiré magnetic excitons, the optical control of spin textures, magneto-photonic devices, magnetic exciton polariton condensation, and the conversion of microwave signals into optical signals for quantum communication.
Other co-authors include Florian Dirnberger of the Technical University of Munich; Swagata Acharya of the National Laboratory of the Rockies; Akashdeep Kamra of Rheinland-Pfälzische Technische Universität Kaiserslautern-Landau; and Xiaodong Xu of the University of Washington.
The work at CCNY was supported by DARPA and the Gordon and Betty Moore Foundation.