Magnetic Coulomb Phase in the Spin Ice Ho ₂ Ti ₂ O ₇

TLDR

Magnetic monopoles, predicted but not observed in particle physics, are theoretically expected to emerge as emergent excitations in spin‑ice materials such as Ho₂Ti₂O₇ and Dy₂Ti₂O₇. Polarized neutron scattering on Ho₂Ti₂O₇ and Dy₂Ti₂O₇ reveals signatures consistent with magnetic monopoles, supporting their presence in these spin‑ice compounds.

Abstract

Magnetic Monopoles Magnets come with a north and a south pole. Despite being predicted to exist, searches in astronomy and in high-energy particle physics experiments for magnetic monopoles (either north or south on their own) have defied observation. Theoretical work in condensed-matter systems has predicted that spin-ice structures may harbor such elusive particles (see the Perspective by Gingras ). Fennell et al. (p. 415 , published online 3 September) and Morris et al. (p. 411 , published online 3 September) used polarized neutron scattering to probe the spin structure forming in two spin-ice compounds—Ho 2 Ti 2 O 7 and Dy 2 Ti 2 O 7 —and present results in support of the presence of magnetic monopoles in both materials.