The decomposition of the magnetic moments in spin ice into freely moving magnetic monopoles has added a new dimension to the concept of fractionalization, showing that geometrical frustration, even in the absence of quantum fluctuations, can lead to the apparent reduction of fundamental objects into quasi particles of reduced dimension . The resulting quasi-particles map onto a Coulomb gas in the grand canonical ensemble . By varying the chemical potential one can drive the ground state from a vacuum to a monopole crystal with the Zinc blend structure .
The condensation of monopoles into the crystallized state leads to a new level of fractionalization:
the magnetic moments appear to collectively break into two distinct parts; the crystal of magnetic charge and a magnetic fluid showing correlations characteristic of an emergent Coulomb phase .
The ordered magnetic charge is synonymous with magnetic order, while the Coulomb phase space is equivalent to that of hard core dimers close packed onto a diamond lattice . The relevance of these results to experimental systems will be discussed.
 C. Castelnovo, R. Moessner, and S. L. Sondhi, Nature 451, 42 (2008).
 L. D. C. Jaubert and P. C. W. Holdsworth, Nature Physics 5, 258 (2009).
 M. Brooks-Bartlett, A. Harman-Clarke, S. Banks, L. D. C. Jaubert and P. C. W. Holdsworth, In Preparation, (2013).
 C. L. Henley, Annual Review of Condensed Matter Physics 1, 179 (2010).
 D. A. Huse, W. Krauth, R. Moessner, and S. L. Sondhi, Phys. Rev. Lett. 91, 167004 (2003).