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Spin ice, a family of rare-earth pyrochlore magnets, offers perhaps the most celebrated example of a classical spin-liquid state, described by a U(1) gauge theory, complete with magnetic monopole excitations.
This underlying gauge symmetry manifests itself in singular, “point-point” features in neutron scattering experiments.
In this talk we present evidence for a new kind of spin liquid on the pyrochlore lattice [1]. This new spin liquid arises in a realistic model of anisotropic exchange on the pyrochlore lattice. It can be described by tensor field-theory with a continuous gauge symmetry, sharing a number of common features with (linearised) general relativity. And, just as the gauge structure of spin ice is visible through “point-points” in neutron scattering, so fluctuations in this new spin liquid lead to extended “pinch lines” – a prediction which can be tested directly in experiment. We discuss the application of these ideas to two pyrochlore magnets of current interest, Yb2Ti2O7 and Tb2Ti2O7.

[1] O. Benton, L. Jaubert, H. Yan and N. Shannon, arXiv:1510.01007v1

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