Attention was focussed on the ability of a nitrogen-vacancy center to monitor an adjacent mesoscopic nuclear spin bath. For this purpose, comparative experiments were performed in which the nitrogen-vacancy spin evolved under the influence of surrounding 13C nuclei or, alternatively, in the presence of asynchronous alternating current fields engineered to emulate bath fluctuations. The study reveals substantial differences that underscore the limitations of the semi-classical picture when interpreting and predicting the outcome of experiments designed to probe small nuclear spin ensembles. In particular, the study elucidated the nitrogen-vacancy center response to bath fluctuations under common pulse sequences, and explored a detection protocol designed to probe time correlations of the nuclear spin bath dynamics. Furthermore, it was shown that the presence of macroscopic nuclear spin order was key to the emergence of semi-classical spin magnetometry.

Diamond Nitrogen-Vacancy Center as a Probe of Random Fluctuations in a Nuclear Spin Ensemble. A.Laraoui, J.S.Hodges, C.A.Ryan, C.A.Meriles: Physical Review B, 2011, 84[10], 104301