nitrogenvacancy

The nitrogen-vacancy center, often written as nitrogen vacancy or NV center, is a point defect in diamond formed by a substitutional nitrogen atom adjacent to a lattice vacancy. The center most commonly exists in the negatively charged state (NV−), which hosts a spin-1 electronic system useful for quantum sensing and information applications.

In the NV− center, the electronic ground state is a spin triplet (S = 1). The spin sublevels can be optically initialized and read out at room temperature: green light excites the center, and the emitted fluorescence is brighter when the spin is in the ms = 0 state. The energy splitting between the ms = 0 and ms = ±1 levels at zero magnetic field is described by a zero-field splitting parameter D, approximately 2.87 GHz at room temperature, and D shifts with temperature (about tens of kHz per kelvin). Microwave radiation can drive transitions between spin sublevels, enabling optically detected magnetic resonance. The NV center is sensitive to magnetic fields, temperature, and electric fields, with coherence times that can range from microseconds to milliseconds depending on sample purity and isotopic composition. Interactions with nearby 13C nuclei in the diamond lattice cause hyperfine structure in the fluorescence spectrum.

Formation of NV centers can occur during diamond growth by incorporating nitrogen impurities, or post-growth by irradiation to create vacancies followed by annealing to mobilize vacancies so they pair with nitrogen. Isotopic purification (reducing 13C content) and surface engineering further improve coherence properties.

Applications of NV centers include nanoscale magnetometry, thermometry, and electrometry, as well as fundamental studies in quantum information processing. NV-based sensors are used in solid-state systems and, in nanodiamond form, in biological contexts, enabling noninvasive, high-resolution sensing.