Luminescence landscapes of nitrogen-vacancy centers in diamond: quasi-localized vibrational resonances and selective coupling

Among the known color centers of diamond, the nitrogen-vacancy (NV) center composed of a substitutional nitrogen and its nearest carbon vacancy could be the most promising photon emitter. In this work, we present the micro-photoluminescence (mu-PL) landscapes of two quasi-localized vibrational resonances (similar to 45 and similar to 63 meV) associated with the neutral (NV0) and negative (NV-) NV centers, respectively. A symmetric electron-phonon coupling theoretical model was used to simulate the mu-PL spectra with vibronic structures, so that the effective phonon densities of states and Huang-Rhys factors could be obtained for the two charge states of the NV centers. Our study also reveals that the perfect lattice optical phonon mode plays a more significant role in the luminescence of the NV0 state, whereas the quasi-localized vibrational resonance plays the dominant role in the case of NV-. These new results may deepen the existing understanding of the luminescence properties of the NV centers in diamond.