The quasi-particle excitations above the degenerate ground state manifold of model spin ice constitute a Coulomb fluid of “magnetic monopoles” [1]. As a model Coulomb fluid, spin ice is thus susceptible to the Wien effect - a universal and robust charge density enhancement for Coulomb systems in an external field [2], whose origin is in the non-equilibrium response to an external field. I will review the physics of the Wien effect for both a lattice electrolyte [3] and its magnetic equivalent highlighting how the non-equilibrium environment allows a response forbidden by symmetry for a system in equilibrium. I will show that spin ice exhibits the Wien effect in the presence of an AC magnetic field [4] and further show that the monopole density increase is directly related to the non-linear magnetic response providing a signal of the Wien effect that is specific to magnetic systems. I will discuss conditions required to observe our predictions of the AC Wien effect in the non-linear susceptibility of Dy2Ti2O7.
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[1] C. Castelnovo, R. Moessner, and S. L. Sondhi, Nature, 451, 42 (2008), I. A. Ryzhkin, Journal of Experimental and Theoretical Physics 101, 481 (2005).
[2] L. Onsager, The Journal of Chemical Physics 2, 599, (1934).
[3] V. Kaiser, S. T. Bramwell, P. C. W. Holdsworth, R. Moessner, arXiv:1412.4981.
[4] V. Kaiser, S. T. Bramwell, P. C. W. Holdsworth, R. Moessner, Nature Materials, 12, 1033-1037 doi :10.1038/nmat3729, (2013).
| Subject : | : | oral |
| Topics | : | Statistical mechanics and computation of large deviation rate functions |
| PDF version | : |  PDF version |
