We present a proposal for applying nanoscale magnetometry to the search for magnetic monopoles in spin ice materials. At low temperatures, there is a sufficiently low monopole density to enable the direct observation of magnetic fields from individual monopoles. Noise spectroscopy can capture the intrinsic fluctuations associated with monopole dynamics, allowing one to isolate the qualitative effects associated with both the Coulomb interaction between monopoles and the topological constraints implied by Dirac strings. We describe in detail three different nanoscale magnetometry platforms (muon spin rotation, nitrogen-vacancy defects, and nanoscale arrays of superconducting quantum interference devices) that can be used to detect monopoles in these experiments and analyze the advantages of each.
Proposal for the detection of magnetic monopoles in spin ice via nanoscale magnetometry
F. K. K. Kirschner, F. Flicker, A. Yacoby, N. Y. Yao, and S. J. Blundell
Phys. Rev. B 97, 140402(R) (2018)