Abstract
Self-trapping of an exciton interacting with the latticevia a short-range interaction is theoretically studied in two types ofquasi-low dimensional systems: anisotropic materials and quantum wellstructures. With a trial exciton wavefunction we variationallycalculate the minimum energy of the system. The results are comparedto those predicted in exact two- and one-dimensional systems. Inanisotropic systems the transition between the free (F) state and theself-trapped (S) state is a sudden change when the coupling constant gexceeds a certain critical value gc, being qualitatively the sameas in three-dimensional isotropic systems. As the anisotropyincreases, however, the height of the potential barrier separating Fand S decreases, and in the one-dimensional limit gc decreases tozero. In quantum well structures, as the width of a slab or a wirebecomes small, the character of the F-S transition gradually changesinto those in two-dimension or one-dimension respectively. Inwire-type quantum wells, a large-radius localized state characteristicof a one-dimensional system appears and coexists with the normalsmall-radius S state characteristic of a three-dimensional system.
