Investigation of Self-Trapped Excitons from a Defect Perspective

In the previous chapter, we surveyed the criteria for self-trapping, starting from delocalized electron and exciton states in the solid and considering effects of short-range and long-range coupling to phonons. The self-trapped exciton resembles a crystal defect in many ways, but its ground state is the perfect lattice. This distinction has experimental significance in that the STE “defect” lives only a short time. It has theoretical significance in that an excited state, rather than the ground state, must be sought in computational methods based on energy minimization. Aside from these differences, however, the similarities of self-trapped excitons and crystal defects suggest experimental and theoretical approaches which are helpful in understanding the atomic and electronic structure of self-trapped excitons, the dynamics of the self-trapping process, and the various channels of decomposition or annihilation of STEs.