The diamond Nitrogen-Vacancy center as a probe of random fluctuations in a nuclear spin ensemble

TL;DR

This paper investigates how Nitrogen-Vacancy centers in diamond can be used to detect and analyze fluctuations in nearby nuclear spin environments, revealing limitations of classical models and proposing new protocols for probing spin dynamics.

Contribution

The study compares NV center responses to actual nuclear spins and engineered fields, highlighting semi-classical model limitations and introducing a protocol to measure nuclear spin bath correlations.

Findings

NV centers detect differences between real nuclear spins and engineered fields.

Semi-classical models are insufficient for small nuclear spin ensembles.

A new protocol probes time correlations in nuclear spin bath dynamics.

Abstract

New schemes that exploit the unique properties of Nitrogen-Vacancy (NV) centers in diamond are presently being explored as a platform for high-resolution magnetic sensing. Here we focus on the ability of a NV center to monitor an adjacent mesoscopic nuclear spin bath. For this purpose, we conduct comparative experiments where the NV spin evolves under the influence of surrounding 13C nuclei or, alternatively, in the presence of asynchronous AC fields engineered to emulate bath fluctuations. Our 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, our study elucidates the NV center response to bath fluctuations under common pulse sequences, and explores a detection protocol designed to probe time correlations of the nuclear spin bath dynamics. Further, we show that the presence of macroscopic nuclear spin order is key to the emergence of semi-classical spin magnetometry.