Wednesday, June 19, 2013

1306.4120 (Marion Brooks-Bartlett et al.)

Monopole Crystallization and Magnetic Moment Fractionalization on a
Pyrochlore Lattice

Marion Brooks-Bartlett, Simon T. Banks, Ludovic D. C. Jaubert, Adam Harman-Clarke, Peter C. W. Holdsworth
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 classical geometrical frustration can lead to the apparent reduction of fundamental objects into quasi-particles of reduced dimension. The resulting quasi-particles map onto a grand canonical Coulomb gas. By varying the chemical potential one can drive the ground state from a vacuum to a monopole crystal analogous to the zinc blende structure but with a new level of fractionalization: the intrinsic magnetic moments appear to collectively break into two distinct parts; the monopole crystal and a magnetic fluid showing correlations characteristic of an emergent Coulomb phase different from the monopole vacuum. The monopole crystal is synonymous with magnetic order, while the Coulomb phase space is equivalent to that of close packed dimers on a diamond lattice. These concepts are tested by numerical simulation and their relevance to experimental systems is discussed.
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