Dr. Agnieszka Kozub, AG Schmidt
What is the challenge of my research project?
The theoretical description of optical response functions of solids is a complex and fascinating many-body problem. Our project aims at the thorough understanding and predictive atomistic modeling of the linear and non-linear optical properties of realistic photonic materials and nanostructures.
In my work, I focus on the development and application of efficient but accurate ab-initio methods that give access to the nonlinear optical spectra, e.g. χ2 and χ3.
Time-dependent density functional theory (TDDFT) is able to account for many-body effects in the optical response calculation, allowing an efficient modelling of real structures, including imperfections.
In my calculations, two methods are used to account for many-body effects in the optical response calculation: (i) perturbed TDDFT (TDDFpT) and (ii) a Berry-phase formulation of the dynamical polarization.
Both methods can be implemented in a way that they rely solely on summations involving occupied orbitals and thus drastically reduces the numerical effort and convergence issues arising from the calculation of large numbers of virtual states.