Bosonic Lasing of Collective Exciton Magnetic Polarons in CuCl₂-Doped CdS Nanoribbons: Implications for Quantum Light Sources

The diluted magnetic semiconductor (DMS) is an important system for realizing room-temperature ferromagnetism. In the DMS, the exchange interactions between the spins of the carrier or exciton and spins of magnetic ions are the cause of the magnetic polaron effect by the self-trapping of the carriers or excitons, leading to the formation of small ferromagnetic domains. Their collective behaviors are expected, though many difficulties have appeared. Spin-polarized excitons coupled with longitudinal optical phonons could form exciton magnetic polarons (EMPs) in a micrometer-sized DMS structure. Here, we studied CuCl2-doped CdS nanoribbons, synthesized by chemical vapor deposition, in which the EMP formation was identified, and a single mode lasing from the ollective EMPs under a femtosecond laser pump was observed at room temperature, similar to an exciton–polariton condensation binding by a spontaneous magnetic moment. Such behavior happened because of the dynamic scattering of exciton condensate by femtosecond exciton excitation. This bosonic lasing behavior may be used for a new-type of quantum light source and other quantum technology.