Probing a spin transfer controlled magnetic nanowire with a single nitrogen-vacancy spin in bulk diamond

The point-like nature and exquisite magnetic field sensitivity of the nitrogen vacancy (NV) center in diamond can provide information about the inner workings of magnetic nanocircuits in complement with traditional transport techniques. Here we use a single NV in bulk diamond to probe the stray field of a ferromagnetic nanowire controlled by spin transfer (ST) torques. We first report an unambiguous measurement of ST tuned, parametrically driven, large-amplitude magnetic oscillations. At the same time, we demonstrate that such magnetic oscillations alone can directly drive NV spin transitions, providing a potential new means of control. Finally, we use the NV as a local noise thermometer, observing strong ST damping of the stray field noise, consistent with magnetic cooling from room temperature to $\sim$150 K.Comment: 6 pages, 5 figures, plus supplementary informatio

Temperature Dependent Photophysics of Single NV Centers in Diamond

We present a comprehensive study of the temperature and magnetic-field dependent photoluminescence (PL) of individual NV centers in diamond, spanning the temperature-range from cryogenic to ambient conditions. We directly observe the emergence of the NV's room-temperature effective excited state structure and provide a clear explanation for a previously poorly understood broad quenching of NV PL at intermediate temperatures around 50 K. We develop a model that quantitatively explains all of our findings, including the strong impact that strain has on the temperaturedependence of the NV's PL. These results complete our understanding of orbital averaging in the NV excited state and have significant implications for the fundamental understanding of the NV center and its applications in quantum sensing.Comment: 5 pages, 4 figures plus Supplementary Material. Questions and comments are welcome. arXiv admin note: text overlap with arXiv:2105.0807

Low temperature photo-physics of single NV centers in diamond

International audienceWe investigate the magnetic field dependent photo-physics of individual Nitrogen-Vacancy (NV) color centers in diamond under cryogenic conditions. At distinct magnetic fields, we observe significant reductions in the NV photoluminescence rate, which indicate a marked decrease in the optical readout efficiency of the NV's ground state spin. We assign these dips to excited state level anti-crossings, which occur at magnetic fields that strongly depend on the effective, local strain environment of the NV center. Our results offer new insights into the structure of the NVs' excited states and a new tool for their effective characterization. Using this tool, we observe strong indications for strain-dependent variations of the NV's orbital g-factor, obtain new insights into NV charge state dynamics, and draw important conclusions regarding the applicability of NV centers for low-temperature quantum sensing