Memory effects in Electron DYNamics: a connector Approach

Many materials properties are determined by the dynamics of electrons and spectroscopic features due to electronic excitations.

One of the most efficient approaches to describe these properties in principle is Time-Dependent Density Functional Theory (TDDFT).

In this framework, however, many interesting phenomena, such as Rabi oscillations or satellites in excitation spectra, depend on the history of the evolution of the system in time. This fact is completely neglected in the most commonly used, adiabatic, approximations. The researcher, Dr. Lionel Lacombe and the host supervisor, Prof.

Lucia Reining, aim at developing new practical schemes to identify and retrieve memory dependent effects in materials.

This requires the development of efficient density functionals as a key ingredient to access new physics stemming from non-adiabatic phenomena at a low numerical cost.

The strategy links computation on model systems and realistic materials through a formal approach, termed Connector Theory (COT). In the model systems, this requires the development of new diagrammatic Green’s functions expansions. Both widely used models, in particular the homogeneous electron gas, and more flexible systems will be considered.

For the real materials, only simple approximations have to be evaluated, since COT allows to improve the results by orders of magnitude using the model knowledge. The method will be applied to predict the charge and spin dynamics, and photoabsorption spectra.

Moreover, the model results will be tabulated and made freely available, which opens the way for understanding and predictions of many more materials and phenomena.