Fig. 2: Hyperfine energy level structure in the ground state and coherence of the NV− center in diamond.
a–c Coupling of the electron spin to the 15N and a nearby 13C nuclear spin close to zero magnetic fields with a polar angle θ0 = 60∘. The abscissa of all figures shows the total magnitude of the applied magnetic field. A transverse zero-field splitting of E = 1.25 MHz is applied to mimic the effect of the surface. a, b Depict the case when there is 0 and 1 13C nuclear spin coupled to the NV− center. Shift of position of the level avoided crossings induced by the E splitting is proportional to the Azz hyperfine coupling term. c Shows multiple closely positioned splits due to two additional weakly coupled 13C nuclear spins. d Calculated free induction decay time curves of the NV− center as a function of applied magnetic fields for different values of the E-splitting. e Calculated T2 time as a function of distance from the surface for a shallow NV center at selected magnetic fields. f Comparison between the T2 curves computed for the NV centers in fluorinated and mixed terminations.
