The question addressed here is: What originates pure spin superradiance in a polarized spin system placed inside a resonantor? The term “pure” means that no initial coherence is imposed on spins, and its appearance manifests a purely self-organized collective effect. An accurate solution of evolution equations for a microscopic model is given. The results show that the resonator Nyquist noise does not play any role in starting spin superradiance, but the emergence of the latter is initiated by local spin fluctuations due to nonsecular dipole interactions.

• Received 10 April 1995

DOI:https://doi.org/10.1103/PhysRevLett.75.3000