Hyperfine interaction in the ground state of the negatively charged nitrogen vacancy center in diamond

Abstract

The $^{14}\text{N}$, $^{15}\text{N}$, and $^{13}\text{C}$ hyperfine interactions in the ground state of the negatively charged nitrogen vacancy $({\text{NV}}^{\ensuremath{-}})$ center have been investigated using electron-paramagnetic-resonance spectroscopy. The previously published parameters for the $^{14}\text{N}$ hyperfine interaction do not produce a satisfactory fit to the experimental ${\text{NV}}^{\ensuremath{-}}$ electron-paramagnetic-resonance data. The small anisotropic component of the ${\text{NV}}^{\ensuremath{-}}$ hyperfine interaction can be explained from dipolar interaction between the nitrogen nucleus and the unpaired-electron probability density localized on the three carbon atoms neighboring the vacancy. Optical spin polarization of the ${\text{NV}}^{\ensuremath{-}}$ ground state was used to enhance the electron-paramagnetic-resonance sensitivity enabling detailed study of the hyperfine interaction with $^{13}\text{C}$ neighbors. The data confirmed the identification of three equivalent carbon nearest neighbors but indicated the next largest $^{13}\text{C}$ interaction is with six, rather than as previously assumed three, equivalent neighboring carbon atoms.