Searching for Exotic Spin-Dependent Interactions with Diamond-Based Vector Magnetometer

We propose a new method to search for exotic spin-spin interactions between electrons and nucleons using a diamond-based vector magnetometer. The vector magnetometer can be constructed from ensembles of nitrogen-vacancy centers along different axes in a diamond. The \(^{14}\mathrm{N} \) nuclear spins of nitrogen-vacancy centers in the same diamond can be polarized through the dynamic nuclear polarization method to serve as spin sources. With the vector magnetometer, the sought-after exotic interactions can be distinguished from the magnetic dipole-dipole interaction. For the axion-mediated interaction \( V_{PP} \), new upper bounds of the coupling \( |g_{P}^{e} g_{P}^{N}| \) are expected within the force range from 10 nm to 100 \( \mu \)m. For the \( Z' \)-mediated interaction \( V_{AA} \), new upper bounds of the coupling \( |g_{A}^{e} g_{A}^{N}| \) are expected within the force range from 10 nm to 1 cm. The new upper bounds for \( V_{PP} \) and \( V_{AA} \) are both expected to be more than 5 orders of magnitude more stringent than existing constraints at the force range of 1 \( \mu \)m with the total measurement time of one day.