Layered semiconductor unlocks magnetic control of light emitted by quantum condensates

In the realm of quantum technologies, researchers have made significant strides in unlocking magnetic control of light emitted by quantum condensates. Bose–Einstein condensates, which exhibit quantum-mechanical effects at macroscopic scales, have traditionally required ultracold temperatures and specialized laboratory conditions. However, recent advancements in solid-state materials have enabled the observation of these condensates at more moderate temperatures.

Typically, excitons, which are electron-hole pairs in a semiconductor, are used to generate Bose–Einstein condensates. These excitons are coupled to the light field of an optical resonator, reducing their effective mass and allowing for selective generation using laser pulses. When exciton–polariton condensation occurs, the intensity of the emitted light increases significantly, and the light waves become coherent, indicating the formation of a macroscopic quantum state.

A key challenge in manipulating the properties of these condensates and, consequently, the emitted light has been overcome by an international research team. By utilizing a novel layered magnetic semiconductor called chromium sulfide bromide (CrSBr), the team demonstrated that exciton–polariton condensates can be controlled through the material's magnetic properties. Unlike conventional semiconductor materials, CrSBr consists of atomically thin layers with alternating magnetic orientations.

The research team, led by Professor Rupert Huber, Dr. Fabian Mooshammer, Dr. Jan Wilhelm, Dr. Florian Dirnberger, and Professor Zdeněk Sofer, first confirmed the occurrence of exciton–polariton condensation in CrSBr structures using ultrashort laser pulses. As the density of exciton–polaritons increased, they eventually synchronized, leading to a hundredfold increase in emitted light intensity.

Importantly, applying an external magnetic field altered the energy of the emitted light, a phenomenon attributed to the unique magnetic order of CrSBr.

This novel control mechanism holds immense potential for future applications in quantum communication, quantum optics, and quantum computing. The ability to directly manipulate the quantum state of the exciton–polariton condensate through the magnetic order of the material opens up new avenues for integrating the platform into magnetic memory devices and efficiently converting microwave radiation into optical signals.