Properties of Correlated Electronic States of Conjugated Systems
Prof. S. Ramasesha, Solid State and Structural Chemistry Unit
Indian Institute of Science, Bangalore 560 012, India
e-mail
Jeudi 24 mai 2007, 14h30
Conjugated organic systems have attracted much attention in recent
times due to the possibility of their use as active species in
molecular electronic devices. Therefore, a comprehensive understanding
of their electronic structure has become very important. Although
conjugated systems were some of the earliest systems studied in quantum
chemistry, the models as well as the methods employed did not consider
the role of electron correlations adequately. While the development of
exact diagonalization techniques was reasonably adequate for
understanding the low-lying states in polyenes, other polymers of
interest such as poly para phenylenes and poly para phenylene vinylenes
could not be adequately studied by these methods. Introduction of the
density matrix renormalization group (DMRG) method which is highly
accurate for quasi-one-dimensional systems provided the impetus to
study conjugated polymers.
In this talk after a brief overview of
models for conjugated systems, developments of exact diagonalization
and DMRG methods for studying low-lying states as well as dynamical
nonlinear optic responses using these methods will be discussed. Some
of our recent studies using real time quantum-many-body dynamics for
understanding intermolecular electronic processes such as electron-hole
recombination, triplet-triplet annihilation and excitation transfer
processes would also be discussed.