Amplification of two-photon photoexcitation due to nonradiative energy transfer

E. L. Gorelova, V. V. Gusev, Ekaterina Dmitrieva +4 more

Lawrence L. Hope, Milton O. Vassell

Alexander A. Zabolotskii

This paper describes the nonradiation (Forster) energy transfer between a dye J-aggregate and closely located nanoparticles possessing the properties of two-level systems. Nanoparticles can be quantum dots (QDs) or a spherical symmetric package of atoms. The dynamics of the process is described by deriving the equations that characterize the density matrix dynamics in a two-level medium and the evolution of exciton pulses in an extended quasi-one-dimensional dye J-aggregate. It is shown that effective controlled resonant transfer of the energy stored in QDs is implemented in the system and manifested in the amplification of the exciton pulses. In turn, there is a possibility of the reverse process of exciton energy transfer in partial inversion of two-level transitions of QDs. The results of this paper are confirmed by the experimental data from the literature.

Mami Segawa, Akira Takahashi, Masaki Aihara

Abstract We theoretically investigate the effect of static disorder on the dynamics of photoexcited states in onedimensional Mott insulators. We adopt the Pariser‐Parr‐Pople model, where disorder is introduced in the site energy and the transfer integral. We numerically calculate the time development of the state excited by a light pulse, and investigate the time dependence of the nearest‐neighbor spin‐spin interaction energy, the on‐site Coulomb interaction energy, and the kinetic energy of photogenerated charges. In the weaker excitation case, the energy transfer from the charge degrees of freedom to the spin degrees of freedom does not occur in the regular systems as a result of the spin‐charge separation. When the disorder in the transfer integral is introduced, the spin‐spin interaction energy changes with time after photoexcitation, showing that the spin‐charge coupling is induced in this case. The effects of the disorder in the site energy on the spincharge coupling are much weaker than those in the transfer integral. On the contrary, the energy transfer from the on‐site Coulomb interaction energy to the kinetic energy is strongly suppressed by these two kinds of disorders. In the stronger excitation case, the spin and the charge degrees of freedom are coupled in the photoexcited states, and the two kinds of energy transfers occur even in regular systems. Furthermore, these energy transfers occur in irreversible way, suggesting that these transfers are relaxation phenomena. These relaxations are enhanced by the disorders. There are no significant differences in the effects of disorders on these relaxations between the disorder in the site energy and that in the transfer integral. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Victor R. Blok

Richard E. Wallenstein