Anderson's localization of molecular excitons in substitutionally disordered systems
We present clear evidence for the presence of Anderson's localization in molecular solids. Diagonal and off-diagonal disorder is introduced and controlled by substitutionally disordering the lattice at different temperatures. Optical and optically-detected magnetic resonance spectroscopy have been used to directly obtain the resonance interactions, the inhomogeneous site-energy fluctuations, and the threshold for Anderson's transition. The results on the two-dimensional lattice when compared with quasi-one-dimensional systems indicate that cross chain interactions and phonon-assisted processes are important in determining the nature of extended states in disordered systems.