Pinch points and Kasteleyn transitions in kagome ice

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Complex disordered states—from liquids and glasses to exotic quantum matter—are ubiquitous in nature. Their key properties include finite entropy, power-law correlations and emergent organizing principles. In spin ice, spin correlations are determined by the ‘ice rules’ organizing principle that stabilizes a magnetic state with the same zero-point entropy as water ice. The entropy can be manipulated with great precision by an applied magnetic field: when directed along the three-fold crystallographic axis, the field produces a state of finite entropy, known as kagome ice. Here, we investigate the spin-ice material Ho2Ti2O7 by tilting the magnetic field slightly away from that axis. We thus realize a classic statistical system named after Kasteleyn, in which the entropy of a critical phase can be continuously tuned. Our neutron scattering experiments reveal how this process occurs at a microscopic level.

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Figure 1: Spin ice and kagome ice.
Figure 2: Measured and simulated diffuse scattering in Ho2Ti2O7.
Figure 3: Pinch-point scattering in kagome ice.
Figure 4: Kasteleyn physics.
Figure 5: Critical-point termination of kagome-ice plateau.


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It is a pleasure to acknowledge the sample environment team at ISIS (in particular R. Down and J. Keeping) and the ILL (J.-L. Ragazzoni and O. Losserand) and we would like to thank A. S. Wills, R. Moessner and P. C. W. Holdsworth for valuable discussions. We thank the EPSRC (UK) for financial support; work in London was also supported by a Wolfson Royal Society Research Merit Award.

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Correspondence to T. Fennell.

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Fennell, T., Bramwell, S., McMorrow, D. et al. Pinch points and Kasteleyn transitions in kagome ice. Nature Phys 3, 566–572 (2007) doi:10.1038/nphys632

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