DEFECTS IN ORDERED EXCITON SYSTEMS

Qualitative analysis and computer simulations show that an ordered system of charge-transfer excitons has a domain structure. The concentration c of defects (domain walls) in a one-dimensional crystal in the stationary state depends on the pumping intensity I as c approximately I-1/2. The density-density correlation function decreases exponentially, the correlation length r0 approximately I1/2. A different behaviour is exhibited by domains in two- and three-dimensional crystals. Small domains disappear, large domains grow in time and the system tends to an ideal one. The domain wall motion is diffusive-like, the healing time increases with the increase of the size of a small domain.