Cooperative Robustness to Static Disorder: Superradiance and   localization in a nanoscale ring to model natural light-harvesting systems
  We analyze a 1-d ring structure composed of many two-level systems, in the limit where only one excitation is present. The two-level systems are coupled to a common environment, where the excitation can be lost, which induces super and subradiant behavior, an example of cooperative quantum coherent effect. We consider time-independent random fluctuations of the excitation energies. This static disorder, also called inhomogeneous broadening in literature, induces Anderson localization and is able to quench Superradiance. We identify two different regimes: $i)$ weak opening, in which Superradiance is quenched at the same critical disorder at which the states of the closed system localize; $ii)$ strong opening, with a critical disorder strength proportional to both the system size and the degree of opening, displaying robustness of cooperativity to disorder. Relevance to photosynthetic complexes is discussed. 
G. L. Celardo, G. G. Giusteri, F. Borgonovi
cond-mat.mes-hall