Dynamical downfolding for localized quantum states

We introduce an approach to treat localized correlated electronic states in the otherwise weakly correlated host medium. Here, the environment is dynamically downfolded on the correlated subspace. It is captured via renormalization of one and two quasiparticle interaction terms which are evaluated using many-body perturbation theory. We outline the strategy on how to take the dynamical effects into account by going beyond the static limit approximation. Further, we introduce an efficient stochastic implementation that enables treating the host environment with a large number of electrons at a minimal computational cost. For a small explicitly correlated subspace, the dynamical effects are critical. We demonstrate the methodology by reproducing optical excitations in the negatively charged NV center defect in diamond, that agree with experimental results.

Automated summary

We present a method to treat localized correlated electronic states in a weakly correlated host medium. The method involves dynamically downfolding the environment on the correlated subspace and renormalizing the quasiparticle interaction terms using many-body perturbation theory. We go beyond static limit approximation to account for dynamical effects and introduce an efficient stochastic implementation for large host environments. We demonstrate the method by reproducing optical excitations in the NV center defect in diamond.