Superradiance in Dissipative Dipolar Systems

In the Superradiance phenomenon, a collection of non-interacting atoms exhibits collective dissipation due to interaction with a common radiation field, resulting in a non-monotonic decay profile. This presentation shows that the dissipative dipolar-coupled systems exhibit an identical collective dissipation aided by the nonsecular part of the dipolar coupling. We consider a simplified dipolar network where the dipolar interaction between the spin-pairs is assumed to be identical. To include the nonsecular dipolar relaxation, we use a fluctuation-regulated quantum master equation. Moreover, we show that for an ensemble of spins, the maximum intensity of the radiation exhibits a nearly quadratic scaling, and the dipolar relaxation time follows an inverse square proportionality; these two observations help characterize the emergence of superradiance. Our results agree well with the standard results of pure spin superradiance observed experimentally in NMR.