Hyperfine level structure in nitrogen-vacancy centers near the ground-state level anticrossing

TL;DR

This paper investigates the hyperfine level structure of nitrogen-vacancy centers near the ground-state level anticrossing using spectroscopy and develops a theoretical model to describe level mixing and transition properties, aiding quantum sensing applications.

Contribution

It introduces a comprehensive theoretical model for hyperfine interactions in NV centers near GSLAC, validated by experimental ODMR data, enhancing understanding for quantum sensing.

Findings

Identified hyperfine-induced level mixing near GSLAC.

Fitted ODMR spectra with the theoretical model.

Provided insights into nuclear spin polarization.

Abstract

Energy levels of nitrogen-vacancy centers in diamond were investigated using optically detected magnetic-resonance spectroscopy near the electronic ground-state level anticrossing (GSLAC) at an axial magnetic field around 102.4~mT in diamond samples with a nitrogen concentration of 1~ppm and 200~ppm. By applying radiowaves in the frequency ranges from 0 to 40 MHz and from 5.6 to 5.9 GHz, we observed transitions that involve energy levels mixed by the hyperfine interaction. We developed a theoretical model that describes the level mixing, transition energies, and transition strengths between the ground-state sublevels, including the coupling to the nuclear spin of the NV center\textquotesingle s $^{14}$N and $^{13}$C atoms. The calculations were combined with the experimental results by fitting the ODMR spectral lines based on a theoretical model, which yielded information about the polarization of nuclear spins. This study is important for the optimization of experimental conditions in GSLAC-based applications, e.g., microwave-free magnetometry and microwave-free nuclear-magnetic-resonance probes.