Observing Magnetic Monopoles in Spin Ice via Electron Holography*

While the magnetic monopole proposed by Pierre Curie and Paul Dirac have remained elusive, emergent monopoles of the H field have been shown to exist in spin ice [1]. Signatures of these monopoles have been indirect so far, leaving their direct observation an open challenge since their discovery [2]. One such technique that could realize this direct observation is electron holography, due to the electron's sensitivity to magnetic fields via the Aharonov-Bohm effect [3]. We explore the possibility of imaging monopoles via electron holography through experimental measurements of monopole and spin ice analogs, and computational simulation of how monopoles would appear in a pyrochlore spin ice thin film [4]. These results suggest that imaging the dynamics of monopoles in thin films of spin ice, including the emergence of electric fields associated with fluctuations of closed loops of spins, through  electron holography is a realistic possibility.

[1] Castelnovo, C., et al. Nat 451(7174), 42–45 jan (2008).

[2] Castelnovo, C., et al. Annu Rev Conden Ma P 3(1), 35–55 (2012).

[3] Park, H. S., et al. Nat Nano 9(5), 337–342 may (2014).

[4] Jaubert, L., et al. Phys Rev Lett 118(20), 207206 may (2017).