Self-Trapping of an Exciton in Quasi-Low Dimensional Systems

概要

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Self-trapping of an exciton interacting with the lattice via a short-range interaction is theoretically studied in two types of quasi-low dimensional systems : anisotropic materials and quantum well structures. With a trial exciton wavefunction we variationally calculate the minimum energy of the system. The results are compared to those predicted in exact two- and one-dimensional systems. In anisotropic systems the transition between the free (F) state and the self-trapped (S) state is a sudden change when the coupling constant g exceeds a certain critical value g_c, being qualitatively the same as in three-dimensional isotropic systems. As the anisotropy increases, however, the height of the potential barrier separating F and S decreases, and in the one-dimensional limit g_c decreases to zero. In quantum well structures, as the width of a slab or a wire becomes small, the character of the F-S transition gradually changes into those in two-dimension or one-dimension respectively. In wire-type quantum wells, a large-radius localized state characteristic of a one-dimensional system appears and coexists with the normal small-radius S state characteristic of a three-dimensional system.
社団法人日本物理学会の論文
1995-08-15