Event Details

Spin ice, with its magnetic monopole excitations, is perhaps the outstanding example a classical, topological spin liquid. Nonetheless, the role of quantum effects in spin-ice materials remains poorly understood. This question gain fresh urgency from studies of "quantum spin-ice" materials such as Yb2Ti2O7 [1,2] and Pr2Zr2O7 [3], and recent experiments which suggest that the spin ice Dy2Ti2O7 may undergo a phase transition at very low temperature [4].

In this talk, we explore some of the new phenomena which can arise as a result of quantum fluctuations in a spin-ice material. We show how quantum tunnelling between different spin-ice configurations can convert spin-ice into a quantum spin liquid with photon-like excitations [5], review the numerical evidence that such a state exists [6-9], and discuss how it might be identified in experiment [8,9].

We also consider the nature of the quantum ground state in a realistic model of spin ice, directly motivated by Dy2Ti2O7. We identify the principles which govern magnetic order in the presence of long-range dipolar interactions, and use quantum Monte Carlo simulation to show that only a very small amount of quantum tunnelling is needed to convert these ordered states into a quantum spin liquid [10].

[1] K. Ross et al., Phys. Rev. X 1, 021002 (2012).
[2] L.-J. Chang et al., Nature Commun. 3, 992 (2012)
[3] K. Kimura et al., Nature Commun. 4, 1934 (2013)
[4] D. Pomaranski et al., Nature Phys. 9, 353 (2013).
[5] M. Hermele et al., Phys. Rev. B 69, 064404 (2004).
[6] A. Banerjee et al., Phys. Rev. Lett. 100, 047208 (2008)
[7] N. Shannon et al., Phys. Rev. Lett. 108, 067204 (2012).
[8] O. Benton et al., Phys. Rev. B 86, 075154 (2012).
[9] Y. Kato et al., arXiv:1411.1918
[10] P. McClarty et al., arXiv:1410.0451