Quantum embedding study of strain and charge induced Stark effects on the NV⁻ center in diamond

The NV⁻ color center in diamond has been demonstrated as a powerful nanosensor for quantum metrology, due to the sensitivity of its optical and spin properties to external electric, magnetic, and strain fields. In view of these applications, we use quantum embedding to derive a many-body description of strain and charge induced Stark effects on the NV⁻ center. We quantify how strain longitudinal to the axis of NV⁻ shifts the excited states in energy, while strain with a component transverse to the NV axis splits the degeneracies of the ³E and ¹E states. The largest effects are for the optically relevant ³E manifold, which splits into Eₓ and Ey with transverse strain. From these responses we extract strain susceptibilities for the Ex/y states within the quasi-linear regime. Additionally, we study the many-body dipole matrix elements of the NV⁻ and find a permanent dipole 1.64 D at zero strain, which is ~ 30 % smaller than that obtained from recent density functional theory calculations. We also determine the transition dipole between the Eₓ and Ey and how it evolves with strain.