Dynamics of open and closed many-electron systems: non-equilibrium Green’s functions made fast

COMP Seminar – Speaker: Prof. Robert van Leeuwen, University of Jyväskylä, Finland

In this presentation, we will discuss the application of non equilibrium Green’s function to many-electron and electron-boson systems out of equilibrium, for both open and closed systems. The general formalism based on the Kadanoff-Baym equations [1] will be discussed as well as a an approximate scheme in which these equations are transformed to one-time equations by expressing the Green’s function as a functional of the one-particle density matrix. We demonstrate that this approximate scheme is a good and fast approximation to the full two-time approach which allows for a first-principle approach to many-electron systems. Applications are presented to transient quantum transport and pump-probe transient-absorption spectroscopy. In particular we explain a recent short laser pulse experiment on the ionisation and photo-absorption of Krypton atoms [2].

[1] G. Stefanucci and R. van Leeuwen, Nonequilibrium Many-body Theory of Quantum Systems: A Modern Introduction, Cambridge University Press (2013)

[2] E. Perfetto, A.-M. Uimonen,  R. van Leeuwen, and G. Stefanucci. First-principles nonequilibrium Green's-function approach to transient photoabsorption: Application to atoms. 
Physical Review A, 92 (3), 033419 (2015)