Low-field feature in the magnetic spectra of NV⁻centers in diamond

Abstract

The low-magnetic-field feature in the magnetic field dependence of the luminescence of negatively charged nitrogen-vacancy (NV − ) centers in diamond has been experimentally observed for the first time. This feature, centered at the zero magnetic field-henceforth the zero field line-and observed with a magnetic field sweep of NV − center luminescence (magnetic spectrum), is quite narrow. The properties of this line are considerably different from those of other narrow NV − magnetic spectrum lines. Its amplitude is weakly dependent on the orientation of the single-crystal sample with respect to the external magnetic field. This line is also observed in a powdered sample. The shape of the line changes drastically with a change in the polarization of excitation light. The amplitude of the line nonlinearly depends on excitation light intensity. For low intensities this dependence is close to the square law. We attribute the occurrence of this line to the dipole-dipole interaction between different NV − centers.

A method for simulating level anti-crossing spectra of diamond crystals containing NV− color centers

“…same amplitude for the different orientations considered here; consequently, the total polarization does not have a feature at zero field. This is consistent with the assumption [28] that this line is merely due to the polarization transfer between NV − centers with different orientations. In experiments this line becomes visible only because the luminescence intensity of the differently oriented NV − centers is not the same (due to the different absorption efficiency of the incident light).…”

“…In experiments this line becomes visible only because the luminescence intensity of the differently oriented NV − centers is not the same (due to the different absorption efficiency of the incident light). As a consequence, the zero-field LAC line (in contrast to all other LAC lines) is a second-order effect and its intensity quadratically depends on the light intensity [28]. Hence, our calculation can account for additional LAC lines at around 500 G and 590 G, which were reported before and come from polarization exchange between different defect centers.…”

“…Since such defect centers are often "dark" centers, information about such interactions can be deduced indirectly from Level Anti-Crossng (LAC) spectra. Experimentally such LAC spectra of diamond single crystals containing NV − centers can be studied by monitoring the magnetic field dependence of the photoluminescence intensity, which contains sharp features associated with LACs [21][22][23][24][25][26][27][28][29][30][31][32][33][34][35]. To probe such "LAC lines" no resonant microwave or radiofrequency pumping is required.…”

“…As we show below, for simulating some LAC lines one should treat a mutil-spin system, which dramatically increases the dimensionality of the spin Hamiltonian matrices. In principle, full quantum mechanical treatment of polarization transfer, which would explicitly include the dynamics in both triplet states, 3 A and 3 E, is possible [28,34,42,43]; however, it requires introducing the density matrix of a multi-level system (including the energy levels of the excited states) and working in the Liouville space rather than in the Hilbert space. As a consequence, the dimensionality of the Liouville super-matrices becomes too large and numerical solution of the equation for the density matrix of the system becomes extremely time consuming, if at all possible.…”

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

“…In this work, we report a study of LAC-lines in diamond single crystals by using modulation of the external magnetic field. Generally, LAC-lines are observed by monitoring photoluminescence as a function of the external magnetic field; a prerequisite for such experiments [29][30][31][32][33][34][35][36][37] is precise orientation of the diamond crystal (so that the magnetic field is parallel to [111] crystal axis with a precision of better than one tenth of a degree). Typically, the LAC-line at 1024 G is relatively easy to detect; however, observation of weaker satellite lines coming from interaction with other paramagnetic centers is technically more demanding.…”