Nitrogen-vacancy (NV) centers placed within about 1 nanometer of a diamond surface would make the most sensitive nanoscale magnetometers, but that close to the surface their spin coherence is destroyed by magnetic noise from the fluctuating nuclear spins of the surface termination. Using first-principles simulations, this work shows that the interplay between surface-induced strain at the NV site and a small applied constant magnetic field can be tuned to substantially extend the spin coherence time of a 1-nm-deep NV, pushing it toward the intrinsic spin-phonon-limited regime at room temperature in isotopically 12C-enriched diamond. The same protocol benefits deeper (about 10 nm) NVs in natural diamond, and because the achievable coherence depends on the direction of the applied field relative to the strain, it simultaneously enables vector magnetometry at the nanoscale.
Recent advances in the engineering of diamond surfaces make it possible to stabilize the charge state of 7-30 nanometers deep nitrogen-vacancy (NV) quantum sensors in diamond and to remove the charge…