Tuesday, June 18, 2013

1306.3790 (Peter Puschnig et al.)

Excited State Properties of Organic Semiconductors: Breakdown of the
Tamm-Dancoff Approximation

Peter Puschnig, Christian Meisenbichler, Claudia Draxl
The solution of the Bethe-Salpeter equation within the framework of many-body perturbation theory has turned out to be a benchmark for ab-initio calculations of optical properties of semiconductors and insulators. Commonly, however, the coupling between the resonant and anti-resonant excitations is neglected which is referred to as the Tamm-Dancoff approximation (TDA). This is well justified in cases where the exciton binding energy is much smaller than the band gap. Here, we report on the optical properties of a representative series of organic semiconductors where we find the TDA to no longer hold. We observe an increase of the exciton binding energy of up to 44% thereby improving the agreement with experiment.
View original: http://arxiv.org/abs/1306.3790

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