Ultrafast Dynamics of Strongly Correlated Fermions -- Nonequilibrium Green Functions and Selfenergy Approximations

Understand

This article presents an overview on recent progress in the theory of nonequilibrium Green functions (NEGF).

• NEGF, presently, are the only \textit{ab-initio} quantum approach that is able to study the dynamics of correlations for long times in two and three dimensions.
• However, until recently, NEGF simulations have mostly been performed with rather simple selfenergy approximations such as the second-order Born approximation (SOA).
• While they correctly capture the qualitative trends of the relaxation towards equilibrium, the reliability and accuracy of these NEGF simulations has remained open, for a long time.