Excited states of strongly correlated point defects using quantum embedding methods

Quantum embedding (QE), which involves combining mean-field and many-body methods, has been demonstrated as a promising approach for calculating properties of point defects relevant for quantum applications. The treatment of excited states, especially when they have multideterminant character, is one such case that is beyond the reach of conventional techniques based on density-functional theory. I will describe three technologically relevant cases of QE applied to defect excited states. First, using the nitrogen-vacancy center in diamond as an example, I will show that we can obtain quantitative accuracy for the optical transition dipole moments between excited states, as well as the permanent dipole moments that govern the susceptibility of the defect states to strain and electric fields. Then, I will discuss the more strongly correlated case of iron impurities in AlN, which have a complex manifold of excited states that may be relevant for nonradiative recombination. I will show how we can benchmark QE against ab-initio many-body methods. Finally, I will discuss methods for generating QE effective models for optical properties of erbium impurities in WS2.