Blog – Page 17

Researchers at City College of New York physicist Vinod M. Menon’s Laboratory for Nano and Micro Photonics (LaNMP) have outlined an emerging frontier in quantum materials: atomically thin systems in which light, magnetism and electric charge are strongly intertwined. This rapidly evolving field could enable next-generation optoelectronic and quantum technologies leveraging the coupled dynamics of light, charge and spin.

A review article in Nature Materials titled “Excitons in van der Waals magnetic materials” surveys recent advances by the CCNY team in layered magnetic semiconductors, where light-generated electronic excitations known as excitons interact with magnetic order and spin waves known as magnons.

Excitons form when light excites an electron within a material, leaving behind a positively charged “hole.” The electron and hole remain bound together as a neutral but optically active particle. Magnons, by contrast, are collective ripples in a material’s magnetic order.

Researchers at RPTU University Kaiserslautern-Landau have achieved a key experimental breakthrough: For the first time, the spontaneous macroscopic coherence of magnons—the quantized excitations of magnetic materials—has been directly observed. These experiments confirm a central prediction of the theory of magnon Bose-Einstein condensates. Eventually, these findings could open new avenues for signal processing, sensing technologies and information processing. The study has been published in Nature Physics.

The three classical states of matter—solid, liquid and gas—are everyday phenomena. However, additional states exist, including plasma and the Bose-Einstein condensate (BEC). In a BEC, a large number of quantum particles no longer behave independently but instead collectively occupy a single macroscopic quantum state.

BECs were originally observed in ultracold atomic gases near absolute zero temperature. Twenty years ago, however, researchers demonstrated that a comparable phase transition can also occur in magnetic solids—notably at room temperature. The corresponding study was carried out by the Department of Physics of TU Kaiserslautern (now RPTU Kaiserslautern-Landau), in collaboration with researchers from the Universities of Münster, Oakland and Kyiv.