Background
The current state-of-the-art ab-initio computations on solids are essentially always based on the so-called Born-Oppenheimer (BO) approximation. There are some rare, but interesting cases, where the BO approximation may fail and we may have to go beyond it for accurate results. Conventional methods, like the original wave function approach, is not computationally feasible in solids as it has poor scaling as a function of system size.
With these points in mind, we have developed reformulations of the Coulombic many-body quantum mechanical problem by using field theoretic approaches that are valid beyond the BO approximation. These approaches are more feasible from the computational point of view than the wave function approach and allows the computation of any observable.
Goals
Development of more sophisticated theoretical tools to describe in more detail systems like molecules and solids.
Implementation of the developed theoretical tools to study realistic systems by computations.
With the theoretical and computational tools developed, to gain understanding of relevant phenomena, like high temperature superconductivity.
Impact
Our developed methods are of a very general nature and are applicable to a wide range of molecules and solids. The impact is difficult to predict, but the potential is high, as our methods can be used to obtain precise observables, with the only assumption being that the interactions arise from the Coulomb force. The beyond-BO regime in solids is largely uncharted, and some experiments suggest a breakdown of the BO approximation in solids composed of light elements. We firmly believe that there are many interesting beyond-BO phenomena yet to be discovered in solids. To address these unknowns, we are working on developing theoretical and computational tools beyond the BO approximation, which could be implemented in the near future.