## Dissipative dynamics of discrete quantum systems coupled to a continuous spectrum: modelling the optical response of functionalized semiconductors

Daniel Finkelstein-Shapiro

Department of Chemistry and Biochemistry, Arizona State University, Phoenix, Arizona, Etats-Unis.

Mardi 10 Juin 2014, 11^{h}00

bibliothèque LCT, tour 12 - 13, 4e étage

Functionalized semiconducting nanoparticles are at the focus of intense research given their possible application in solar energy, electronic devices and biocompatible functional materials. Although the constituents can be very simple, the response of the system remains very complex. This stems in part from the strong mixing of ligand states with the bands of the semiconductor and in part from the heterogeneity of environments experienced by the ligand.

This seminar will summarize our efforts in the study of the optical response and electron dynamics of small aromatic molecules adsorbed on anatase nanoparticles by a combined theoretical, computational and experimental approach. We use a minimum ingredient model of the ligand-nanoparticle and solve it using the Liouville equation with a relaxation operator that conforms to the Lindblad form which ensures complete positivity of the density matrix. We then calculate the full optical response, and in particular the Surface Enhanced Raman Spectrum which was recently discovered to also exist in semiconductors lacking a plasmon resonance. In order to correctly calculate the parameters of the model, a good understanding of the surface geometries is needed. We use DFT methods to calculate surface geometries and NMR chemical shifts which we can compare to experiments in order to determine the exact geometries of adsorption and extract electronic couplings.