Regensburg 2010 – scientific programme

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O: Fachverband Oberflächenphysik

O 78: Symposium Density functional theory and beyond for real materials

O 78.4: Invited Talk

Thursday, March 25, 2010, 16:30–17:00, H1

Giant polaronic effects in solids and nanstructures — •Andrea Marini — CNISM and department of Physics, University of Rome Tor Vergata

The conjugation of Ab-Initio methods with Many-Body techniques, constitutes a well-established approach to interpret the photoexcited properties of bulk materials, surfaces, nanostructures and organic/bio-molecules. In the standard approach, however, atoms are assumed to be frozen in their crystallographic positions, thus neglecting the effect of lattice vibrations. As a consequence quasiparticles and excitons turn out to be insensitive to the temperature T and with an infinite lifetime, in stark contrast with the experimental evidence. In the frozen-atom approaches this temperature dependence is not described at all and, even in the T → 0 limit, the calculated absorption spectra is commonly convoluted with some artificial, ad-hoc numerical broadening function chose to yield the best agreement with the experiment. In this talk I will show how to solve, in a fully Ab-Initio manner, the equation of motion of quasiparticles and excitons including the coupling with the lattice vibrations. The picture obtained within a frozen-atom approximation will turn out to be deeply modified by the electron-phonon coupling, either at zero and finite temperature. I will discuss several important consequences as the bright to dark (and vice versa) transitions of excitons in layered materials, or the beakdown of the quasiparticle picture in conjugated polymers.