Optical sensing of weak magnetic fields in superconductors using NV centers in diamond
ORAL
Abstract
Visible light fluorescent nitrogen-vacancy centers in diamond have emerged as high sensitivity sensors for nanoscale magnetometry. Here, we study spatial distributions of the magnetic induction upon penetration and expulsion of weak magnetic fields in several representative superconductors. In particular, vector magnetic field was measured with diffraction-limited spatial resolution on the surface of elemental (Pb and Nb), intermetallic (LuNi2B2C), and iron-based (Ba0.6K0.4Fe2As2, Ba(Fe0.93Co0.07)2As2, CaKFe4As4) superconductors in zero-field-cooling (ZFC) and field-cooling (FC) experiments. While ZFC shows robust screening, the structure of the Meissner state after FC ranges from conventional flux expulsion in Pb and LuNi2B2C, to paramagnetic Meissner effect in Nb, to virtually no expulsion in iron-based superconductors. We further apply this technique for accurate measurements of the first critical field and use it to estimate London penetration depth in several superconductors (arXiv:1709.02769).
*This work was supported by the US DOE, Office of Science, BES Materials Science and Engineering Division under contract # DE-AC02-07CH11358. W.M. was supported by the Gordon and Betty Moore Foundation's EPiQS Initiative through Grant GBMF4411.
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Presenters
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Naufer Nusran
- Ames Lab
- Ames Laboratory