Multi-dimensional quantum spectroscopy

Single atomic defects in diamond can serve as magnetic field sensors with exquisite sensitivity and nanoscale resolution, providing an attractive alternative to traditional detectors in nuclear magnetic resonance experiments. Indeed, single nitrogen–vacancy (NV) centers have been used to determine the positions of ~30 proximal atoms. However, most of this work has been performed on an idealized "test bed system", individual ¹³C atoms inside the diamond host lattice surrounding the NV center.

In this talk, we focus on the differences of nuclear spin environments of spins residing inside the diamond and on the surface of the diamond. For sparse ¹³C spin environments, the hyperfine coupling to the NV center is the dominant coupling while nuclear-nuclear couplings are minor. This is opposite for surface spins where the nuclear-nuclear coupling is dominant and presents the primary source for structure determination of macromolecules and molecular complexes covalently bound to the diamond surface.

We show newly developed spectroscopy sequences that allow to cover both regimes in multi-dimensional experiments. We show an improved localization of nuclear spins inside the diamond by encoding the nuclear spin position into frequencies only. This removes ambiguities found in past analysis schemes that used e.g., the line-shape and signal amplitude of a weak-measurement spectrum. Furthermore, we demonstrate a sequence for measuring the nuclear-nuclear couplings. We demonstrate the measurement of internuclear couplings of ¹³C spins inside the diamond at room temperature and give an outlook on the steps needed to combine our recent advances in surface preparation with these new sequences.