Sensitive detection of level anticrossing spectra of nitrogen vacancy centers in diamond

Abstract

We report a study of the magnetic field dependence of photoluminescence of ${\mathrm{NV}}^{\ensuremath{-}}$ centers (negatively charged nitrogen vacancy centers) in diamond single crystals. In such a magnetic field dependence characteristic sharp features are observed, which are coming from level anticrossings (LACs) in a coupled electron-nuclear spin system. For studying such LAC lines we use sensitive lock-in detection to measure the photoluminescence intensity. This experimental technique allows us to obtain new LAC lines. Additionally, a remarkably strong dependence of the LAC lines on the modulation frequency is found. Specifically, upon decrease of the modulation frequency from 12 kHz to 17 Hz the amplitude of the LAC lines increases by approximately two orders of magnitude. To take a quantitative account for such effects, we present a theoretical model, which describes the spin dynamics in a coupled electron-nuclear spin system under the action of an oscillating external magnetic field. Good agreement between experiments and theory allows us to conclude that the observed effects are originating from coherent spin polarization exchange in a coupled spin system comprising the spin-polarized ${\mathrm{NV}}^{\ensuremath{-}}$ center. Our results are of great practical importance allowing one to optimize the experimental conditions for probing LAC-derived lines in diamond crystals comprising ${\mathrm{NV}}^{\ensuremath{-}}$ centers and for indirect detection and identification of other paramagnetic defect centers.