Roi Baer, PhD
Heising-Simons Visiting Fellow of the Kavli Energy NanoScience Institute
Fritz Haber Center for Molecular Dynamics Institute of Chemistry
The Hebrew University of Jerusalem
We present theoretical approaches for studying quasiparticle and optical excitation in large systems. We start with first-principles tuning of range-separated hybrid (RSH) functionals, a technique based on density functional theory and then we introduce a stochastic approach to G0W0 and the Bethe Salpeter Equation, based on many-body perturbation theory. We show that RSH tuning allows for practical and effective correction of many ailments of DFT-based calculations but as system size grow its efficacy diminishes unless quasiparticles localize. Recently we found that in finite 1D polymers, such as polythiophene or trans polyacetylene quasiparticles localize with length scales of dozens of nanometers due to a purely electronic effect. Results from G0W0, applied to these large polymers strands seem to support this conclusion.