Coexistence of large-radius and small-radius polaron states in a quantum wire

Summary

The self-trapping of a Frenkel exciton in quantum wells of various dimensionalities and thicknesses is theoretically studied. Using a (2J _x +1)×(2J _y +1)×(2J _z +1) lattice-site model, we variationally calculate the relaxed exciton state for various strength of the coupling constantg of the short-range exciton-lattice interaction. In slab-type QWs (∞×∞×(2J _z +1)), asg increases the stable state abruptly changes from the free stateF to the self-trapped stateS as in the exact three-dimension. In wire-type QWs (∞×(2J _y +1)×(2J _z +1)), wheng is small the stable state is a weakly localized state (large-radius polaron), which corresponds toF ing=0 limit, but the Stokes shift of the emission from thisF state is non-zero. Wheng becomes large this large-radius polaron state,F, characteristic of a one-dimensional system coexists with a small-radius polaron state,S, characteristic of a three-dimensional system.