Many-body description of shallow NV− centers in diamond: role of surface coupling on quantum sensors and qubits

Strongly correlated defect states found in negatively charged nitrogen-vacancy (NV−) centers offer an excellent platform for the control of individual excitations due to the defect's highly localized nature. This means the center's spatially localized bound states are well isolated from sources of decoherence, making it a leading candidate for quantum sensors and solid state qubit systems. To guarantee good sensing capabilities, engineering the defect as close as possible to the surface (a few nanometers in depth) is preferable. Nevertheless, shallow NV- centers are prone to decoherence due to the coupling to the surface impurities. In this work, we study sub-surface NV- centers in diamond using various surface types (100 and 111) and surface terminations (hydrogen and nitrogen terminators). Using density functional theory and many-body perturbation theory methods, we provide an accurate theoretical description for understanding various couplings and control mechanisms in these shallow NV- centers. We discuss the stability of the defect embedded into large slabs (up to 8 nm thickness) which constitute more than 13,000 electrons. Our results show the first realistic simulation of sub-surface NV- defects within the framework of stochastic many-body theory.