Modelling nonequilibrium physics with ab initio real time propagation schemes. From coherent excitons to exciton-phonon coupling.

I will present recent and ongoing developments in the real-time module of the yambo code [1] aimed at modelling nonequilibrium dynamics in advanced materials from first-principles. In the code we employ two differnt strategies. The first is based on the propagation of the electronic one-body density matrix, [2] while the second on the propagation of one particle electronic wave-functions. [3] In both schemes we include many-body effects via updating on the fly the long range many-body self-energy, within the Hartree plus screened Exchange (HSEX) approximation, also referred to as adiabatic GW (aGW), to capture the generation of coherent excitons.

I will show applications of the approach in modelling pump and probe experiments and discuss how it can be used to complement standard GW and BSE simulations. Example of applications will range from LiF [4,5], a prototype materials hosting strongly bound exctions, to layered materials [6].

Among the ongoing developments, I will discuss the coupling of the electronic equation of motion with the time propagation of the atomic coordinates, to capture the real-time coupling between excitons and phonons. The real-time (coherent) exciton-phonon coupling will be compared with Fermi golden rule approaches to exciton-phonon coupling from first principles [7].