• Title:Level anti-crossing studies in nitrogen – vacancy centers in diamond crystals
  • Start Date/Time:2017-04-27 / 14:00
  • End Date/Time :2017-04-27 / 16:00
    • Speaker:Porf. Marcis Auzins (University of Latvia)
    • Place:Lecture Room A of NCTS, 4F, 3rd General Building, Nat'l Tsing Hua Univ.
    • Host:Prof. Ray-Kuang Lee (NTHU)
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      Abstract: Over the recent years, negatively charged nitrogen-vacancy centers (NV) in diamond have emerged as a promising future technology for sensing applications. That is due to their high sensitivity and inherent scalability, which ranges from single NV centers, offering a few nanometres spatial resolution, to bulk sensors, providing enhanced field sensitivity. Despite these advantages, however, several important fundamental and technological challenges of NV-based sensing remain open.

      Recent developments in magnetic field sensing with negatively charged nitrogen-vacancy centers in diamond employ magnetic-field dependent features in the photoluminescence. These features can be studied in presence of the microwave radiation or this radiation can be eliminated [1].

      In the present study in addition of the laser radiation which polarized the NV centers in the ground state, we employ microwave field in different frequency ranges. When the microwave field frequency is in the range of 5,9 GHz and the magnetic field around 0.1 T is applied, we are studying microwave radiation caused resonant depolarisation of the NV centres in the ground state due to transitions between mixed levels in the vicinity of anti-crossing point and distant spin state magnetic sub-level. Dependence of the contrast of optically detected magnetic resonances and width of these resonances on the strength of the magnetic field is measured. Measured signals are compared with a numerical model that accounts for the hyperfine interaction of NV electronic angular momentum with the nitrogen nuclear spin and magnetic field.

      If the microwave field frequency is much lower, below 100 MHz, but strength of the external magnetic field still is around 0.1 T, we are studying NV centre angular momentum resonant depolarisation by the microwave radiation causing transitions between magnetic sub-levels in the vicinity of the anti-crossing point. Again, the width and contrast of these signals as they depend on the external magnetic field, are measured. The experimental results are compared with the numerical model.

      Finally, the effect of cross relaxation between NV centres and substitutional nitrogen [2] on the optically detected magnetic resonances in the vicinity of the magnetic field of 0.05 T – their contrast and width, is studied.

      All the studies are supported by the model of NV centre interaction with light in the presence of magnetic field and microwave radiation, based on our previous experience of similar studies in atomic systems [3].

      [1] Huijie Zheng et. al arXiv:1701.06838v1, 24 Jan 2017
      [2] L.T. Hall et al Nature Communications, 5 January 2016
      [3] M. Auzinsh, D. Budker, S. Rochester Optically Polarised Atoms, Oxford University Press, 2014.
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