Title: Proposal for the Detection of Magnetic Monopoles in Spin Ice via Nanoscale Magnetometry,
Abstract: We present a proposal for applying nanoscale magnetometry to the search for
magnetic monopoles in the spin ice materials holmium and dysprosium titanate.
Employing Monte Carlo simulations of the dipolar spin ice model, we find that
when cooled to below $1.5\,$K these materials exhibit a sufficiently low
monopole density to enable the direct observation of magnetic fields from
individual monopoles. At these temperatures we demonstrate that 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
nanoSQUID arrays) that can be used to detect monopoles in these experiments,
and analyze the advantages of each.