AI-rewritten: This is a summary of an article from Phys.org, rewritten by AI (Qwen, running locally) to make it easier to read. The facts come from the original article – read it for the full story.

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Researchers have developed a method to control light emitted by quantum condensates using the magnetic properties of a new layered semiconductor called chromium sulfide bromide (CrSBr). Unlike traditional semiconductors that require extreme cooling, this material allows exciton–polaritons to form at moderate temperatures. Exciton–polaritons are hybrid states created when electron-hole pairs, known as excitons, couple with light in an optical resonator. This coupling reduces their effective mass, enabling them to move in lockstep and form a macroscopic quantum state that emits coherent light.

The breakthrough involves the unique magnetic structure of CrSBr, which consists of atomically thin layers where electron spins point in opposite directions in neighboring layers. These spins act like tiny compass needles, creating a magnetic cage that confines excitons to specific layers. By applying an external magnetic field, researchers can align these spins in the same direction, breaking the confinement and selectively adjusting the energy of the emitted light. This control is highly efficient; moderate magnetic fields produce energy shifts up to 10 times larger than previous methods relying on electrical voltage.

The study, led by a team from the University of Regensburg, the Technical University of Munich, and the University of Chemistry and Technology Prague, was published in the journal Nature Materials. The team demonstrated that as exciton–polariton density increases, they eventually oscillate in sync, causing light intensity to increase more than 100fold. This coherence confirms condensation has occurred. Future applications could include integrating this platform into magnetic memory devices and converting microwave radiation into optical signals efficiently. This work establishes a new interface between quantum states and magnetic order, laying the foundation for advanced quantum technologies without the need for specialized laboratory cooling conditions.