Dynamical downfolding for localized quantum states

TL;DR

This paper presents a novel dynamical downfolding method to accurately model localized electronic states in weakly correlated materials, incorporating environment effects via renormalized interactions and stochastic computation.

Contribution

It introduces a dynamic environment treatment for localized states using renormalized interactions and an efficient stochastic implementation, advancing beyond static approximations.

Findings

Successfully reproduces optical excitations in NV centers

Demonstrates the importance of dynamical effects in small correlated subspaces

Provides a scalable approach for large environment systems

Abstract

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 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 are in excellent agreement with experimental results.