Polymers on the verge of strongly correlated systems and 1d semiconductors
* SPEAKERS
Name
Affiliation
E-mail
N. Kirova
CNRS, LPS, Univ. Paris-Sud
* HOST(Applicant)
Name
Affiliation
E-mail
-
* DATE / TIME
2004-11-25, 2:30 - 4:00 p.m.
* PLACE
Bldg 3, Room#201, POSTECH
* ABSTRACT
We review the recent progress in the unified theory for optical and electronic properties of conducting polymers. We consider both the generic features as 1D semiconductors and particularities of the most important in applications phenyl group. Bringing together languages of the solid state theory and the quantum chemistry allows us to take into account strong electronic correlations upon the semiconductor type approach. The theory operates with a few parameters which can be determined experimentally or from ab initio calculations. The model explains, exploits and organizes various experimental and numerical findings. We connect such different questions as coexistence of shallow singlet and deep triplet excitons in phenylenes, crossing of Bu and Ag levels in polyenes, common 1/L energy dependencies in oligomers. We can interpret several observed time delay regimes in luminescence, fluorescence and phosphorescence due to conversion between various types of excitons. In details we consider the fundamental edge structure and describe the suppression of the DOS singularity by the long range Coulomb interactions in the final state of the e-h pair. We study the series of the shallow excitons, particularly at presence of the strong electric field. The last allows explaining new sharp spectral features observed in photoconductivity. The specific on-site e-h repulsion can lead to inversion of optically allowed and forbidden transitions
